我正在尝试将我的ngrx状态封装在共享服务类中,以从我的组件中抽象出实现细节.
在app.module.ts提供程序中注册的示例服务类
@Injectable()
export class PatientService {
state: Observable<PatientState>;
constructor(
private store: Store<AppState>,) {
this.state = store.select<PatientState>('patients');
}
}
我已经验证了我的操作,reducer和effect正在按预期工作,但是,当我订阅组件中的服务状态时,它返回undefined.
使用共享服务的示例组件订阅：
@Component({
...
})
export class DashboardComponent implements OnInit {
constructor(
private patientService: PatientService,) {}
ngOnInit(): void {
// dispatches action to load patient from API
this.patientService.loadPatient();
this.patientService.state.subscribe(patientState => {
console.log('patientState',patientState);
// Does not work. Logs undefined.
});
}
}
如果我直接订阅商店,它会按预期工作.
例：
@Component({
...
})
export class DashboardComponent implements OnInit {
constructor(
private patientActions: PatientActions,private store: Store<AppState>,) {}
ngOnInit(): void {
this.store.dispatch(this.patientActions.loadPatient());
this.store.select<PatientState>('patients').subscribe(patientState => {
console.log('patientState',patientState);
// Works as expected.
});
}
}
我究竟做错了什么？
我已经实现了类似的用例.你的尝试很好,我用这种方式工作：
@Injectable()
export class PatientService {
// Define Observable
patientState$: Observable<PatientState>;
constructor(private store: Store<AppState>) {
// Get data from the store
this.patientState$= store.select<PatientState>('patients');
}
getState(): PatientState {
// subscribe to it so i don't have to deal with observables in components
let patientState: PatientState = null;
this.patientState$.subscribe(ps => patientState = ps);
return patientState;
}
}
@Component({
...
})
export class DashboardComponent implements OnInit {
patientState = new PatientState;
constructor(
private patientService: PatientService,) {}
ngOnInit(): void {
// Simply get the Object from the store without dealing with observables
this.patientState = this.patientService.getState();
}
}
我在observables的末尾使用$所以我知道每次触摸变量时它是否是Observable,这样我就不会感到困惑.
