feat(signals): replace idKey with selectId when defining custom entity ID (#4396)

Closes #4217, #4392

Co-authored-by: Tim Deschryver <28659384+timdeschryver@users.noreply.github.com>

Author: markostanimirovic

modules/signals/entities/spec/helpers.ts

@@ -0,0 +1,4 @@
+import { SelectEntityId } from '../src';
+import { Todo } from './mocks';
+
+export const selectTodoId: SelectEntityId<Todo> = (todo) => todo._id;

modules/signals/entities/spec/updaters/add-entities.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntities, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId as selectId } from '../helpers';
 
 describe('addEntities', () => {
   it('adds entities if they do not exist', () => {
@@ -115,36 +116,36 @@ describe('addEntities', () => {
     expect(store.userEntities()).toEqual([user1, user3, user2]);
   });
 
-  it('adds entities with the specified idKey if they do not exist', () => {
+  it('adds entities with a custom id if they do not exist', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
-    patchState(store, addEntities([todo2, todo3], { idKey: '_id' }));
+    patchState(store, addEntities([todo2, todo3], { selectId }));
 
     expect(store.entityMap()).toEqual({ y: todo2, z: todo3 });
     expect(store.ids()).toEqual(['y', 'z']);
     expect(store.entities()).toEqual([todo2, todo3]);
 
     patchState(
       store,
-      addEntities([todo1], { idKey: '_id' }),
-      addEntities([] as Todo[], { idKey: '_id' })
+      addEntities([todo1], { selectId }),
+      addEntities([] as Todo[], { selectId })
     );
 
     expect(store.entityMap()).toEqual({ y: todo2, z: todo3, x: todo1 });
     expect(store.ids()).toEqual(['y', 'z', 'x']);
     expect(store.entities()).toEqual([todo2, todo3, todo1]);
   });
 
-  it('does not add entities with the specified idKey if they already exist', () => {
+  it('does not add entities with a custom id if they already exist', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
     patchState(
       store,
-      addEntities([todo1], { idKey: '_id' }),
-      addEntities([todo2, todo1], { idKey: '_id' }),
-      addEntities([] as Todo[], { idKey: '_id' })
+      addEntities([todo1], { selectId }),
+      addEntities([todo2, todo1], { selectId }),
+      addEntities([] as Todo[], { selectId })
     );
 
     const entityMap = store.entityMap();
@@ -153,8 +154,8 @@ describe('addEntities', () => {
 
     patchState(
       store,
-      addEntities([] as Todo[], { idKey: '_id' }),
-      addEntities([todo2, { ...todo2, text: 'NgRx' }, todo1], { idKey: '_id' })
+      addEntities([] as Todo[], { selectId }),
+      addEntities([todo2, { ...todo2, text: 'NgRx' }, todo1], { selectId })
     );
 
     expect(store.entityMap()).toBe(entityMap);
@@ -164,14 +165,14 @@ describe('addEntities', () => {
     expect(store.ids()).toEqual(['x', 'y']);
     expect(store.entities()).toEqual([todo1, todo2]);
 
-    patchState(store, addEntities([todo1, todo3, todo2], { idKey: '_id' }));
+    patchState(store, addEntities([todo1, todo3, todo2], { selectId }));
 
     expect(store.entityMap()).toEqual({ x: todo1, y: todo2, z: todo3 });
     expect(store.ids()).toEqual(['x', 'y', 'z']);
     expect(store.entities()).toEqual([todo1, todo2, todo3]);
   });
 
-  it('adds entities with the specified idKey to the specified collection if they do not exist', () => {
+  it('adds entities with a custom id to the specified collection if they do not exist', () => {
     const Store = signalStore(
       withEntities({
         entity: type<Todo>(),
@@ -184,7 +185,7 @@ describe('addEntities', () => {
       store,
       addEntities([todo3, todo2], {
         collection: 'todo',
-        idKey: '_id',
+        selectId,
       })
     );
 
@@ -194,20 +195,20 @@ describe('addEntities', () => {
 
     patchState(
       store,
-      addEntities([todo1], { collection: 'todo', idKey: '_id' }),
-      addEntities([] as Todo[], { collection: 'todo', idKey: '_id' })
+      addEntities([todo1], { collection: 'todo', selectId }),
+      addEntities([] as Todo[], { collection: 'todo', selectId })
     );
 
     expect(store.todoEntityMap()).toEqual({ z: todo3, y: todo2, x: todo1 });
     expect(store.todoIds()).toEqual(['z', 'y', 'x']);
     expect(store.todoEntities()).toEqual([todo3, todo2, todo1]);
   });
 
-  it('does not add entities with the specified idKey to the specified collection if they already exist', () => {
+  it('does not add entities with a custom id to the specified collection if they already exist', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/add-entity.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntity, withEntities } from '../../src';
 import { Todo, todo1, todo2, User, user1, user2 } from '../mocks';
+import { selectTodoId as selectId } from '../helpers';
 
 describe('addEntity', () => {
   it('adds entity if it does not exist', () => {
@@ -96,31 +97,31 @@ describe('addEntity', () => {
     expect(store.userEntities()).toEqual([user1]);
   });
 
-  it('adds entity with the specified idKey if it does not exist', () => {
+  it('adds entity with a custom id if it does not exist', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
-    patchState(store, addEntity(todo1, { idKey: '_id' }));
+    patchState(store, addEntity(todo1, { selectId }));
 
     expect(store.entityMap()).toEqual({ x: todo1 });
     expect(store.ids()).toEqual(['x']);
     expect(store.entities()).toEqual([todo1]);
 
-    patchState(store, addEntity(todo2, { idKey: '_id' }));
+    patchState(store, addEntity(todo2, { selectId }));
 
     expect(store.entityMap()).toEqual({ x: todo1, y: todo2 });
     expect(store.ids()).toEqual(['x', 'y']);
     expect(store.entities()).toEqual([todo1, todo2]);
   });
 
-  it('does not add entity with the specified idKey if it already exists', () => {
+  it('does not add entity with a custom id if it already exists', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
     patchState(
       store,
-      addEntity(todo1, { idKey: '_id' }),
-      addEntity(todo2, { idKey: '_id' })
+      addEntity(todo1, { selectId }),
+      addEntity(todo2, { selectId })
     );
 
     const entityMap = store.entityMap();
@@ -129,10 +130,10 @@ describe('addEntity', () => {
 
     patchState(
       store,
-      addEntity(todo1, { idKey: '_id' }),
-      addEntity({ ...todo1, text: 'NgRx' }, { idKey: '_id' }),
-      addEntity(todo2, { idKey: '_id' }),
-      addEntity(todo1, { idKey: '_id' })
+      addEntity(todo1, { selectId }),
+      addEntity({ ...todo1, text: 'NgRx' }, { selectId }),
+      addEntity(todo2, { selectId }),
+      addEntity(todo1, { selectId })
     );
 
     expect(store.entityMap()).toBe(entityMap);
@@ -143,7 +144,7 @@ describe('addEntity', () => {
     expect(store.entities()).toEqual([todo1, todo2]);
   });
 
-  it('adds entity with the specified idKey to the specified collection if it does not exist', () => {
+  it('adds entity with a custom id to the specified collection if it does not exist', () => {
     const Store = signalStore(
       withEntities({
         entity: type<Todo>(),
@@ -152,24 +153,24 @@ describe('addEntity', () => {
     );
     const store = new Store();
 
-    patchState(store, addEntity(todo1, { collection: 'todo', idKey: '_id' }));
+    patchState(store, addEntity(todo1, { collection: 'todo', selectId }));
 
     expect(store.todoEntityMap()).toEqual({ x: todo1 });
     expect(store.todoIds()).toEqual(['x']);
     expect(store.todoEntities()).toEqual([todo1]);
 
-    patchState(store, addEntity(todo2, { collection: 'todo', idKey: '_id' }));
+    patchState(store, addEntity(todo2, { collection: 'todo', selectId }));
 
     expect(store.todoEntityMap()).toEqual({ x: todo1, y: todo2 });
     expect(store.todoIds()).toEqual(['x', 'y']);
     expect(store.todoEntities()).toEqual([todo1, todo2]);
   });
 
-  it('does not add entity with the specified idKey to the specified collection if it already exists', () => {
+  it('does not add entity with a custom id to the specified collection if it already exists', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/remove-all-entities.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { removeAllEntities, setAllEntities, withEntities } from '../../src';
 import { Todo, todo1, todo2, User, user1, user2 } from '../mocks';
+import { selectTodoId } from '../helpers';
 
 describe('removeAllEntities', () => {
   it('removes all entities', () => {
@@ -27,7 +28,7 @@ describe('removeAllEntities', () => {
       store,
       setAllEntities([todo1, todo2], {
         collection: 'todo',
-        idKey: '_id',
+        selectId: selectTodoId,
       })
     );
     patchState(store, removeAllEntities({ collection: 'todo' }));

modules/signals/entities/spec/updaters/remove-entities.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntities, removeEntities, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId } from '../helpers';
 
 describe('removeEntities', () => {
   it('removes entities by ids', () => {
@@ -24,7 +25,7 @@ describe('removeEntities', () => {
 
     patchState(
       store,
-      addEntities([todo1, todo2, todo3], { idKey: '_id' }),
+      addEntities([todo1, todo2, todo3], { selectId: selectTodoId }),
       removeEntities((todo) => todo.completed)
     );
 
@@ -99,7 +100,7 @@ describe('removeEntities', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId: selectTodoId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/remove-entity.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntities, removeEntity, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2 } from '../mocks';
+import { selectTodoId } from '../helpers';
 
 describe('removeEntity', () => {
   it('removes entity', () => {
@@ -18,7 +19,7 @@ describe('removeEntity', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
-    patchState(store, addEntities([todo2, todo3], { idKey: '_id' }));
+    patchState(store, addEntities([todo2, todo3], { selectId: selectTodoId }));
 
     const entityMap = store.entityMap();
     const ids = store.ids();
@@ -39,7 +40,7 @@ describe('removeEntity', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId: selectTodoId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/set-all-entities.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { setAllEntities, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId as selectId } from '../helpers';
 
 describe('setAllEntities', () => {
   it('replaces entity collection with provided entities', () => {
@@ -57,34 +58,34 @@ describe('setAllEntities', () => {
     expect(store.userEntities()).toEqual([]);
   });
 
-  it('replaces entity collection with provided entities with the specified idKey', () => {
+  it('replaces entity collection with provided entities with a custom id', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
-    patchState(store, setAllEntities([todo2, todo3], { idKey: '_id' }));
+    patchState(store, setAllEntities([todo2, todo3], { selectId }));
 
     expect(store.entityMap()).toEqual({ y: todo2, z: todo3 });
     expect(store.ids()).toEqual(['y', 'z']);
     expect(store.entities()).toEqual([todo2, todo3]);
 
-    patchState(store, setAllEntities([todo3, todo2, todo1], { idKey: '_id' }));
+    patchState(store, setAllEntities([todo3, todo2, todo1], { selectId }));
 
     expect(store.entityMap()).toEqual({ z: todo3, y: todo2, x: todo1 });
     expect(store.ids()).toEqual(['z', 'y', 'x']);
     expect(store.entities()).toEqual([todo3, todo2, todo1]);
 
-    patchState(store, setAllEntities([] as Todo[], { idKey: '_id' }));
+    patchState(store, setAllEntities([] as Todo[], { selectId }));
 
     expect(store.entityMap()).toEqual({});
     expect(store.ids()).toEqual([]);
     expect(store.entities()).toEqual([]);
   });
 
-  it('replaces specified entity collection with provided entities with the specified idKey', () => {
+  it('replaces specified entity collection with provided entities with a custom id', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/set-entities.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { setEntities, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId as selectId } from '../helpers';
 
 describe('setEntities', () => {
   it('adds entities if they do not exist', () => {
@@ -115,43 +116,43 @@ describe('setEntities', () => {
     ]);
   });
 
-  it('adds entities with the specified idKey if they do not exist', () => {
+  it('adds entities with a custom id if they do not exist', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
-    patchState(store, setEntities([todo2, todo3], { idKey: '_id' }));
+    patchState(store, setEntities([todo2, todo3], { selectId }));
 
     expect(store.entityMap()).toEqual({ y: todo2, z: todo3 });
     expect(store.ids()).toEqual(['y', 'z']);
     expect(store.entities()).toEqual([todo2, todo3]);
 
     patchState(
       store,
-      setEntities([todo1], { idKey: '_id' }),
-      setEntities([] as Todo[], { idKey: '_id' })
+      setEntities([todo1], { selectId }),
+      setEntities([] as Todo[], { selectId })
     );
 
     expect(store.entityMap()).toEqual({ y: todo2, z: todo3, x: todo1 });
     expect(store.ids()).toEqual(['y', 'z', 'x']);
     expect(store.entities()).toEqual([todo2, todo3, todo1]);
   });
 
-  it('replaces entities with the specified idKey if they already exist', () => {
+  it('replaces entities with a custom id if they already exist', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
     patchState(
       store,
-      setEntities([todo1], { idKey: '_id' }),
-      setEntities([todo2, { ...todo1, text: 'Signals' }], { idKey: '_id' }),
-      setEntities([] as Todo[], { idKey: '_id' })
+      setEntities([todo1], { selectId }),
+      setEntities([todo2, { ...todo1, text: 'Signals' }], { selectId }),
+      setEntities([] as Todo[], { selectId })
     );
 
     patchState(
       store,
-      setEntities([] as Todo[], { idKey: '_id' }),
+      setEntities([] as Todo[], { selectId }),
       setEntities([todo3, todo2, { ...todo2, text: 'NgRx' }, todo1], {
-        idKey: '_id',
+        selectId,
       })
     );
 
@@ -168,7 +169,7 @@ describe('setEntities', () => {
     ]);
   });
 
-  it('adds entities with the specified idKey to the specified collection if they do not exist', () => {
+  it('adds entities with a custom id to the specified collection if they do not exist', () => {
     const Store = signalStore(
       withEntities({
         entity: type<Todo>(),
@@ -181,7 +182,7 @@ describe('setEntities', () => {
       store,
       setEntities([todo3, todo2], {
         collection: 'todo',
-        idKey: '_id',
+        selectId,
       })
     );
 
@@ -191,20 +192,20 @@ describe('setEntities', () => {
 
     patchState(
       store,
-      setEntities([todo1], { collection: 'todo', idKey: '_id' }),
-      setEntities([] as Todo[], { collection: 'todo', idKey: '_id' })
+      setEntities([todo1], { collection: 'todo', selectId }),
+      setEntities([] as Todo[], { collection: 'todo', selectId })
     );
 
     expect(store.todoEntityMap()).toEqual({ z: todo3, y: todo2, x: todo1 });
     expect(store.todoIds()).toEqual(['z', 'y', 'x']);
     expect(store.todoEntities()).toEqual([todo3, todo2, todo1]);
   });
 
-  it('replaces entities with the specified idKey to the specified collection if they already exist', () => {
+  it('replaces entities with a custom id to the specified collection if they already exist', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/set-entity.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { setEntity, withEntities } from '../../src';
 import { Todo, todo1, todo2, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId as selectId } from '../helpers';
 
 describe('setEntity', () => {
   it('adds entity if it does not exist', () => {
@@ -86,33 +87,33 @@ describe('setEntity', () => {
     ]);
   });
 
-  it('adds entity with the specified idKey if it does not exist', () => {
+  it('adds entity with a custom id if it does not exist', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
-    patchState(store, setEntity(todo1, { idKey: '_id' }));
+    patchState(store, setEntity(todo1, { selectId }));
 
     expect(store.entityMap()).toEqual({ x: todo1 });
     expect(store.ids()).toEqual(['x']);
     expect(store.entities()).toEqual([todo1]);
 
-    patchState(store, setEntity(todo2, { idKey: '_id' }));
+    patchState(store, setEntity(todo2, { selectId }));
 
     expect(store.entityMap()).toEqual({ x: todo1, y: todo2 });
     expect(store.ids()).toEqual(['x', 'y']);
     expect(store.entities()).toEqual([todo1, todo2]);
   });
 
-  it('replaces entity with the specified idKey if it already exists', () => {
+  it('replaces entity with a custom id if it already exists', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
     patchState(
       store,
-      setEntity(todo1, { idKey: '_id' }),
-      setEntity(todo2, { idKey: '_id' })
+      setEntity(todo1, { selectId }),
+      setEntity(todo2, { selectId })
     );
-    patchState(store, setEntity({ ...todo2, text: 'NgRx' }, { idKey: '_id' }));
+    patchState(store, setEntity({ ...todo2, text: 'NgRx' }, { selectId }));
 
     expect(store.entityMap()).toEqual({
       x: todo1,
@@ -122,7 +123,7 @@ describe('setEntity', () => {
     expect(store.entities()).toEqual([todo1, { ...todo2, text: 'NgRx' }]);
   });
 
-  it('adds entity with the specified idKey to the specified collection if it does not exist', () => {
+  it('adds entity with a custom id to the specified collection if it does not exist', () => {
     const Store = signalStore(
       withEntities({
         entity: type<Todo>(),
@@ -131,24 +132,24 @@ describe('setEntity', () => {
     );
     const store = new Store();
 
-    patchState(store, setEntity(todo1, { collection: 'todo', idKey: '_id' }));
+    patchState(store, setEntity(todo1, { collection: 'todo', selectId }));
 
     expect(store.todoEntityMap()).toEqual({ x: todo1 });
     expect(store.todoIds()).toEqual(['x']);
     expect(store.todoEntities()).toEqual([todo1]);
 
-    patchState(store, setEntity(todo2, { collection: 'todo', idKey: '_id' }));
+    patchState(store, setEntity(todo2, { collection: 'todo', selectId }));
 
     expect(store.todoEntityMap()).toEqual({ x: todo1, y: todo2 });
     expect(store.todoIds()).toEqual(['x', 'y']);
     expect(store.todoEntities()).toEqual([todo1, todo2]);
   });
 
-  it('replaces entity with the specified idKey to the specified collection if it already exists', () => {
+  it('replaces entity with a custom id to the specified collection if it already exists', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/update-all-entities.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntities, updateAllEntities, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId } from '../helpers';
 
 describe('updateAllEntities', () => {
   it('updates all entities', () => {
@@ -76,7 +77,7 @@ describe('updateAllEntities', () => {
       store,
       addEntities([todo1, todo2, todo3], {
         collection: 'todo',
-        idKey: '_id',
+        selectId: selectTodoId,
       }),
       updateAllEntities({ completed: false }, { collection: 'todo' })
     );

modules/signals/entities/spec/updaters/update-entities.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntities, updateEntities, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId } from '../helpers';
 
 describe('updateEntities', () => {
   it('updates entities by ids', () => {
@@ -37,7 +38,10 @@ describe('updateEntities', () => {
     const Store = signalStore(withEntities<Todo>());
     const store = new Store();
 
-    patchState(store, addEntities([todo1, todo2, todo3], { idKey: '_id' }));
+    patchState(
+      store,
+      addEntities([todo1, todo2, todo3], { selectId: selectTodoId })
+    );
 
     patchState(
       store,
@@ -181,7 +185,7 @@ describe('updateEntities', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId: selectTodoId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));

modules/signals/entities/spec/updaters/update-entity.spec.ts

@@ -1,6 +1,7 @@
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntities, updateEntity, withEntities } from '../../src';
 import { Todo, todo1, todo2, todo3, User, user1, user2, user3 } from '../mocks';
+import { selectTodoId } from '../helpers';
 
 describe('updateEntity', () => {
   it('updates entity', () => {
@@ -56,7 +57,7 @@ describe('updateEntity', () => {
   it('does not modify entity state if entity do not exist', () => {
     const todoMeta = {
       entity: type<Todo>(),
-      idKey: '_id',
+      selectId: selectTodoId,
     } as const;
 
     const Store = signalStore(withEntities(todoMeta));
@@ -102,7 +103,7 @@ describe('updateEntity', () => {
       store,
       addEntities([todo1, todo2, todo3], {
         collection: 'todo',
-        idKey: '_id',
+        selectId: selectTodoId,
       }),
       updateEntity(
         { id: todo1._id, changes: { text: '' } },

modules/signals/entities/spec/with-entities.spec.ts

@@ -2,6 +2,7 @@ import { isSignal } from '@angular/core';
 import { patchState, signalStore, type } from '@ngrx/signals';
 import { addEntities, withEntities } from '../src';
 import { Todo, todo2, todo3, User, user1, user2 } from './mocks';
+import { selectTodoId } from './helpers';
 
 describe('withEntities', () => {
   it('adds entity feature to the store', () => {
@@ -50,7 +51,7 @@ describe('withEntities', () => {
     const todoMeta = {
       entity: type<Todo>(),
       collection: 'todo',
-      idKey: '_id',
+      selectId: selectTodoId,
     } as const;
 
     const Store = signalStore(withEntities<User>(), withEntities(todoMeta));

modules/signals/entities/src/helpers.ts

@@ -4,10 +4,15 @@ import {
   EntityId,
   EntityPredicate,
   EntityState,
+  SelectEntityId,
 } from './models';
 
-export function getEntityIdKey(config?: { idKey?: string }): string {
-  return config?.idKey ?? 'id';
+const defaultSelectId: SelectEntityId<{ id: EntityId }> = (entity) => entity.id;
+
+export function getEntityIdSelector(config?: {
+  selectId?: SelectEntityId<any>;
+}): SelectEntityId<any> {
+  return config?.selectId ?? defaultSelectId;
 }
 
 export function getEntityStateKeys(config?: { collection?: string }): {
@@ -65,9 +70,9 @@ export function getEntityUpdaterResult(
 export function addEntityMutably(
   state: EntityState<any>,
   entity: any,
-  idKey: string
+  selectId: SelectEntityId<any>
 ): DidMutate {
-  const id = entity[idKey];
+  const id = selectId(entity);
 
   if (state.entityMap[id]) {
     return DidMutate.None;
@@ -82,12 +87,12 @@ export function addEntityMutably(
 export function addEntitiesMutably(
   state: EntityState<any>,
   entities: any[],
-  idKey: string
+  selectId: SelectEntityId<any>
 ): DidMutate {
   let didMutate = DidMutate.None;
 
   for (const entity of entities) {
-    const result = addEntityMutably(state, entity, idKey);
+    const result = addEntityMutably(state, entity, selectId);
 
     if (result === DidMutate.Both) {
       didMutate = result;
@@ -100,9 +105,9 @@ export function addEntitiesMutably(
 export function setEntityMutably(
   state: EntityState<any>,
   entity: any,
-  idKey: string
+  selectId: SelectEntityId<any>
 ): DidMutate {
-  const id = entity[idKey];
+  const id = selectId(entity);
 
   if (state.entityMap[id]) {
     state.entityMap[id] = entity;
@@ -118,12 +123,12 @@ export function setEntityMutably(
 export function setEntitiesMutably(
   state: EntityState<any>,
   entities: any[],
-  idKey: string
+  selectId: SelectEntityId<any>
 ): DidMutate {
   let didMutate = DidMutate.None;
 
   for (const entity of entities) {
-    const result = setEntityMutably(state, entity, idKey);
+    const result = setEntityMutably(state, entity, selectId);
 
     if (didMutate === DidMutate.Both) {
       continue;

modules/signals/entities/src/index.ts

@@ -10,5 +10,11 @@ export { updateEntity } from './updaters/update-entity';
 export { updateEntities } from './updaters/update-entities';
 export { updateAllEntities } from './updaters/update-all-entities';
 
-export { EntityId, EntityMap, EntityState, NamedEntityState } from './models';
+export {
+  EntityId,
+  EntityMap,
+  EntityState,
+  NamedEntityState,
+  SelectEntityId,
+} from './models';
 export { withEntities } from './with-entities';

modules/signals/entities/src/models.ts

@@ -21,11 +21,7 @@ export type NamedEntityComputed<Entity, Collection extends string> = {
   [K in keyof EntityComputed<Entity> as `${Collection}${Capitalize<K>}`]: EntityComputed<Entity>[K];
 };
 
-export type EntityIdProps<Entity> = {
-  [K in keyof Entity as Entity[K] extends EntityId ? K : never]: Entity[K];
-};
-
-export type EntityIdKey<Entity> = keyof EntityIdProps<Entity> & string;
+export type SelectEntityId<Entity> = (entity: Entity) => EntityId;
 
 export type EntityPredicate<Entity> = (entity: Entity) => boolean;
 

modules/signals/entities/src/updaters/add-entities.ts

@@ -1,14 +1,14 @@
 import { PartialStateUpdater } from '@ngrx/signals';
 import {
   EntityId,
-  EntityIdKey,
   EntityState,
   NamedEntityState,
+  SelectEntityId,
 } from '../models';
 import {
   addEntitiesMutably,
   cloneEntityState,
-  getEntityIdKey,
+  getEntityIdSelector,
   getEntityStateKeys,
   getEntityUpdaterResult,
 } from '../helpers';
@@ -18,7 +18,7 @@ export function addEntities<Entity extends { id: EntityId }>(
 ): PartialStateUpdater<EntityState<Entity>>;
 export function addEntities<Entity, Collection extends string>(
   entities: Entity[],
-  config: { collection: Collection; idKey: EntityIdKey<Entity> }
+  config: { collection: Collection; selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function addEntities<
   Entity extends { id: EntityId },
@@ -29,18 +29,18 @@ export function addEntities<
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function addEntities<Entity>(
   entities: Entity[],
-  config: { idKey: EntityIdKey<Entity> }
+  config: { selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<EntityState<Entity>>;
 export function addEntities(
   entities: any[],
-  config?: { collection?: string; idKey?: string }
+  config?: { collection?: string; selectId?: SelectEntityId<any> }
 ): PartialStateUpdater<EntityState<any> | NamedEntityState<any, string>> {
-  const idKey = getEntityIdKey(config);
+  const selectId = getEntityIdSelector(config);
   const stateKeys = getEntityStateKeys(config);
 
   return (state) => {
     const clonedState = cloneEntityState(state, stateKeys);
-    const didMutate = addEntitiesMutably(clonedState, entities, idKey);
+    const didMutate = addEntitiesMutably(clonedState, entities, selectId);
 
     return getEntityUpdaterResult(clonedState, stateKeys, didMutate);
   };

modules/signals/entities/src/updaters/add-entity.ts

@@ -1,14 +1,14 @@
 import { PartialStateUpdater } from '@ngrx/signals';
 import {
   EntityId,
-  EntityIdKey,
   EntityState,
   NamedEntityState,
+  SelectEntityId,
 } from '../models';
 import {
   addEntityMutably,
   cloneEntityState,
-  getEntityIdKey,
+  getEntityIdSelector,
   getEntityStateKeys,
   getEntityUpdaterResult,
 } from '../helpers';
@@ -18,7 +18,7 @@ export function addEntity<Entity extends { id: EntityId }>(
 ): PartialStateUpdater<EntityState<Entity>>;
 export function addEntity<Entity, Collection extends string>(
   entity: Entity,
-  config: { collection: Collection; idKey: EntityIdKey<Entity> }
+  config: { collection: Collection; selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function addEntity<
   Entity extends { id: EntityId },
@@ -29,18 +29,18 @@ export function addEntity<
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function addEntity<Entity>(
   entity: Entity,
-  config: { idKey: EntityIdKey<Entity> }
+  config: { selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<EntityState<Entity>>;
 export function addEntity(
   entity: any,
-  config?: { collection?: string; idKey?: string }
+  config?: { collection?: string; selectId?: SelectEntityId<any> }
 ): PartialStateUpdater<EntityState<any> | NamedEntityState<any, string>> {
-  const idKey = getEntityIdKey(config);
+  const selectId = getEntityIdSelector(config);
   const stateKeys = getEntityStateKeys(config);
 
   return (state) => {
     const clonedState = cloneEntityState(state, stateKeys);
-    const didMutate = addEntityMutably(clonedState, entity, idKey);
+    const didMutate = addEntityMutably(clonedState, entity, selectId);
 
     return getEntityUpdaterResult(clonedState, stateKeys, didMutate);
   };

modules/signals/entities/src/updaters/set-all-entities.ts

@@ -1,12 +1,12 @@
 import { PartialStateUpdater } from '@ngrx/signals';
 import {
   EntityId,
-  EntityIdKey,
   EntityState,
   NamedEntityState,
+  SelectEntityId,
 } from '../models';
 import {
-  getEntityIdKey,
+  getEntityIdSelector,
   getEntityStateKeys,
   setEntitiesMutably,
 } from '../helpers';
@@ -16,7 +16,7 @@ export function setAllEntities<Entity extends { id: EntityId }>(
 ): PartialStateUpdater<EntityState<Entity>>;
 export function setAllEntities<Entity, Collection extends string>(
   entities: Entity[],
-  config: { collection: Collection; idKey: EntityIdKey<Entity> }
+  config: { collection: Collection; selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function setAllEntities<
   Entity extends { id: EntityId },
@@ -27,18 +27,18 @@ export function setAllEntities<
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function setAllEntities<Entity>(
   entities: Entity[],
-  config: { idKey: EntityIdKey<Entity> }
+  config: { selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<EntityState<Entity>>;
 export function setAllEntities(
   entities: any[],
-  config?: { collection?: string; idKey?: string }
+  config?: { collection?: string; selectId?: SelectEntityId<any> }
 ): PartialStateUpdater<EntityState<any> | NamedEntityState<any, string>> {
-  const idKey = getEntityIdKey(config);
+  const selectId = getEntityIdSelector(config);
   const stateKeys = getEntityStateKeys(config);
 
   return () => {
     const state: EntityState<any> = { entityMap: {}, ids: [] };
-    setEntitiesMutably(state, entities, idKey);
+    setEntitiesMutably(state, entities, selectId);
 
     return {
       [stateKeys.entityMapKey]: state.entityMap,

modules/signals/entities/src/updaters/set-entities.ts

@@ -1,13 +1,13 @@
 import { PartialStateUpdater } from '@ngrx/signals';
 import {
   EntityId,
-  EntityIdKey,
   EntityState,
   NamedEntityState,
+  SelectEntityId,
 } from '../models';
 import {
   cloneEntityState,
-  getEntityIdKey,
+  getEntityIdSelector,
   getEntityStateKeys,
   getEntityUpdaterResult,
   setEntitiesMutably,
@@ -18,7 +18,7 @@ export function setEntities<Entity extends { id: EntityId }>(
 ): PartialStateUpdater<EntityState<Entity>>;
 export function setEntities<Entity, Collection extends string>(
   entities: Entity[],
-  config: { collection: Collection; idKey: EntityIdKey<Entity> }
+  config: { collection: Collection; selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function setEntities<
   Entity extends { id: EntityId },
@@ -29,18 +29,18 @@ export function setEntities<
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function setEntities<Entity>(
   entities: Entity[],
-  config: { idKey: EntityIdKey<Entity> }
+  config: { selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<EntityState<Entity>>;
 export function setEntities(
   entities: any[],
-  config?: { collection?: string; idKey?: string }
+  config?: { collection?: string; selectId?: SelectEntityId<any> }
 ): PartialStateUpdater<EntityState<any> | NamedEntityState<any, string>> {
-  const idKey = getEntityIdKey(config);
+  const selectId = getEntityIdSelector(config);
   const stateKeys = getEntityStateKeys(config);
 
   return (state) => {
     const clonedState = cloneEntityState(state, stateKeys);
-    const didMutate = setEntitiesMutably(clonedState, entities, idKey);
+    const didMutate = setEntitiesMutably(clonedState, entities, selectId);
 
     return getEntityUpdaterResult(clonedState, stateKeys, didMutate);
   };

modules/signals/entities/src/updaters/set-entity.ts

@@ -1,13 +1,13 @@
 import { PartialStateUpdater } from '@ngrx/signals';
 import {
   EntityId,
-  EntityIdKey,
   EntityState,
   NamedEntityState,
+  SelectEntityId,
 } from '../models';
 import {
   cloneEntityState,
-  getEntityIdKey,
+  getEntityIdSelector,
   getEntityStateKeys,
   getEntityUpdaterResult,
   setEntityMutably,
@@ -18,7 +18,7 @@ export function setEntity<Entity extends { id: EntityId }>(
 ): PartialStateUpdater<EntityState<Entity>>;
 export function setEntity<Entity, Collection extends string>(
   entity: Entity,
-  config: { collection: Collection; idKey: EntityIdKey<Entity> }
+  config: { collection: Collection; selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function setEntity<
   Entity extends { id: EntityId },
@@ -29,18 +29,18 @@ export function setEntity<
 ): PartialStateUpdater<NamedEntityState<Entity, Collection>>;
 export function setEntity<Entity>(
   entity: Entity,
-  config: { idKey: EntityIdKey<Entity> }
+  config: { selectId: SelectEntityId<NoInfer<Entity>> }
 ): PartialStateUpdater<EntityState<Entity>>;
 export function setEntity(
   entity: any,
-  config?: { collection?: string; idKey?: string }
+  config?: { collection?: string; selectId?: SelectEntityId<any> }
 ): PartialStateUpdater<EntityState<any> | NamedEntityState<any, string>> {
-  const idKey = getEntityIdKey(config);
+  const selectId = getEntityIdSelector(config);
   const stateKeys = getEntityStateKeys(config);
 
   return (state) => {
     const clonedState = cloneEntityState(state, stateKeys);
-    const didMutate = setEntityMutably(clonedState, entity, idKey);
+    const didMutate = setEntityMutably(clonedState, entity, selectId);
 
     return getEntityUpdaterResult(clonedState, stateKeys, didMutate);
   };

projects/ngrx.io/content/guide/signals/signal-store/entity-management.md

@@ -217,9 +217,9 @@ patchState(this.todoStore, removeEntities([2, 4]));
 
 The default property name for an identifier is `id` and is of type `string` or `number`.
 
-It is possible to specify a different name, but the type must still be `string` or `number`. You can specify the id only when adding or setting an entity. It is not possible to define it via `withEntities`.
+It is possible to specify a custom ID selector, but the return type must still be a `string` or `number`. Custom ID selectors should be provided when adding or setting an entity. It is not possible to define it via `withEntities`.
 
-Therefore, all variations of the `add*` and `set*` functions have an optional (last) parameter, which is an object literal and allows to define the id property via `idKey`.
+Therefore, all variations of the `add*` and `set*` functions have an optional (last) parameter, which is an object literal that allows to specify the `selectId` function.
 
 For example:
 
@@ -230,18 +230,20 @@ interface Todo {
   finished: boolean;
 }
 
+const selectId: SelectEntityId<Todo> = (todo) => todo.key;
+
 patchState(
   this.todoStore,
   addEntities(
     [
       { key: 2, name: 'Car Washing', finished: false },
       { key: 3, name: 'Cat Feeding', finished: false },
     ],
-    { idKey: 'key' }
+    { selectId }
   )
 );
 
-patchState(this.todoStore, setEntity({ key: 4, name: 'Dog Feeding', finished: false }, { idKey: 'key' }));
+patchState(this.todoStore, setEntity({ key: 4, name: 'Dog Feeding', finished: false }, { selectId }));
 ```
 
 The `update*` and `remove*` methods, which expect an id value, automatically pick the right one. That is possible because every entity belongs to a map with its id as the key.
@@ -306,17 +308,19 @@ The names of the state properties changed from:
 
 All functions that operate on entities require a collection parameter. Those are `add*`, `set*`, `update*`, and `remove*`. They are type-safe because you need to provide the collection to avoid getting a compilation error.
 
-If you have a customized id property, you need to include the `idKey` parameter in the object literal, too:
+If you have a customized id property, you need to include the `selectId` function in the object literal, too:
 
 ```typescript
+const selectId: SelectEntityId<Todo> = (todo) => todo.key;
+
 patchState(
   this.todoStore,
   addEntities(
     [
       { key: 2, name: 'Car Washing', finished: false },
       { key: 3, name: 'Cat Feeding', finished: false },
     ],
-    { idKey: 'key', collection: 'todo' }
+    { selectId, collection: 'todo' }
   )
 );
 ```