setProp
setProp
Accepts an object of type T, a key of type K extends keyof T, and a value of
type T[K]. Sets the property and returns a new, updated object without mutating
the original one.
Immutability is explained in the immutability & serializable state concept.
Example
const cat = { id: 1, type: 'cat', name: 'Fluffy' };
const renamedCat = setProp(cat, 'name', 'Bella');
// renamedCat will be:
// {id: 1, type: 'cat', name: 'Bella'};
Example — with rxState()
import { Component } from '@angular/core';
import { Subject } from 'rxjs';
import { rxState } from '@rx-angular/state';
import { setProp } from '@rx-angular/cdk/transformations';
@Component({
/* ... */
})
export class ProfileComponent {
readonly changeName$ = new Subject<string>();
private readonly state = rxState<ComponentState>(({ connect }) => {
connect(this.changeName$, (state, name) => setProp(state, 'name', name));
});
// Imperative alternative
changeName(name: string): void {
this.state.set(setProp(this.state.get(), 'name', name));
}
}
Example — signals-first
import { signal } from '@angular/core';
import { setProp } from '@rx-angular/cdk/transformations';
const profile = signal<Profile>({ id: 1, type: 'cat', name: 'Fluffy' });
profile.update((state) => setProp(state, 'name', 'Bella'));
Edge cases
setProp(nonObject, 'prop' as any, 42) > { prop: 42 };
setProp(null as any, 'prop', 42) > { prop: 42 };
setProp(null as any, null as any, 42) > null;
setProp([state], 'concat', () => []) > { concat: () => [] };
setProp(state, 'nonExisting' as any, 42) > { ...state, nonExisting: 42 };
setProp(state, null as any, 42) > state;
Signature
function setProp<T extends object, K extends keyof T>(object: T, key: K, value: T[K]): T;