在Angular中使用类Redux工具—ngrx/store

摘要：因为我们正好要使用，此时我们就可以用的服务来监听了当然，我们不能忘了清空订阅最后一步就是在有返回的时候调用表单的现在我们可以在组件里显示提醒了

原文：Connect Angular Forms to @ngrx/store

这篇文章中，我们将要讨论如何用ngrx/effects连接Angular表单和ngrx/store

我们最终的结果是这样的

ew-story0.component.ts

@Component({
  selector: "new-story-form",
  template: `
    

       ...controls
    
    
Success!
    
{{error}}
})
class NewStoryFormComponent {...}

方便起见，我们会写一个简单的reducer来组织管理我们应用里的所有的表单

状态（the state）将由一个用ID作为key，表格数据作为value的简单对象构成

举个例子

connect-form.reducer.ts

const initialState = {
  newStory: {
    title: "",
    description: ""
  },
  contactUs: {
    email: "",
    message: ""
  }
}

export function forms(state = initialState, action) {
}

我们先构建一个action——UPDATE_FORM。这个action由两个key：path和value组成

connect-form1.reducer.ts

store.dispatch({
  type: UPDATE_FORM,
  payload: {
    path: "newStory",
    value: formValue
  }
});

然后这个reducer将负责更新state

connect-form2.reducer.ts

export function forms(state = initialState, action) {
  if(action.type === UPDATE_FORM) { 
                       // newStory:           formValue
    return { ...state, [action.payload.path]: action.payload.value }
  }
}

我们想要基于state更新表单，所以我们需要path作为输入，然后取出store中正确的片段

connect-form.directive.ts

@Directive({
  selector: "[connectForm]"
})
export class ConnectFormDirective {
  @Input("connectForm") path: string;

  constructor(private formGroupDirective: FormGroupDirective,
    private store: Store ) {
      
    ngOnInit() {
      // Update the form value based on the state
      this.store.select(state => state.forms[this.path]).take(1).subscribe(formValue => {
        this.formGroupDirective.form.patchValue(formValue);
      });
    }
  }
}

我们抓取表单directive实例然后从store里更新表单数据

当表单数据改变时我们也需要更新表单状态。我们可以通过订阅（subscribe）这个valueChanges的可观察对象（observable）然后调度（dispatch）这个UPDATE_FORM的action来获取值

connect-form1.directive.ts

this.formChange = this.formGroupDirective.form.valueChanges
  .subscribe(value => {
    this.store.dispatch({
      type: UPDATE_FORM,
      payload: {
        value,
        path: this.path, // newStory
      }
    });
})

这就是表单和State同步所要做的全部工作了

有两件事我们要在这个部分完成

基于HTTP响应返回来显示通知给用户——我们需要保证通知直接传给组件并且不储存信息在store里

有两点原因

通常，没有其他的组件需要这个信息

我们不想每次都重置store

当提交成功时重置表单

我们将让Angular尽其所能，处理好前端表单校验并重置表单

成功的Action包含表单的path属性所以我们可以知道到底哪个表单需要重置，同时什么时候需要去使用（emit）这个成功的事件

connect-form2.directive.ts

const FORM_SUBMIT_SUCCESS = "FORM_SUBMIT_SUCCESS";
const FORM_SUBMIT_ERROR = "FORM_SUBMIT_ERROR";
const UPDATE_FORM = "UPDATE_FORM";

export const formSuccessAction = path => ({
  type: FORM_SUBMIT_SUCCESS,
  payload: {
    path
  }
});

同成功的action一样，因为有path的存在，我们也知道何时去使用（emit）错误异常 的事件

connect-form3.directive.ts

export const formErrorAction = ( path, error ) => ({
  type: FORM_SUBMIT_ERROR,
  payload: {
    path,
    error
  }
});

我们需要创建 成功 和 错误异常 的输出 然后 监听 FORM_SUBMIT_ERROR 和 FORM_SUBMIT_SUCCESS 的 action。

因为我们正好要使用 ngrx/effects ，此时我们就可以用 Action 的服务（service）来监听actions了

connect-form3.directive.ts

@Directive({
  selector: "[connectForm]"
})
export class ConnectFormDirective {
  @Input("connectForm") path : string;
  @Input() debounce : number = 300;
  @Output() error = new EventEmitter();
  @Output() success = new EventEmitter();
  formChange : Subscription;
  formSuccess : Subscription;
  formError : Subscription;

  constructor( private formGroupDirective : FormGroupDirective,
               private actions$ : Actions,
               private store : Store ) {
  }

  ngOnInit() {
    this.store.select(state => state.forms[this.path])
      .debounceTime(this.debounce)
      .take(1).subscribe(val => {
      this.formGroupDirective.form.patchValue(val);
    });

    this.formChange = this.formGroupDirective.form.valueChanges
      .debounceTime(this.debounce).subscribe(value => {
        this.store.dispatch({
          type: UPDATE_FORM,
          payload: {
            value,
            path: this.path,
          }
        });
      });

    this.formSuccess = this.actions$
      .ofType(FORM_SUBMIT_SUCCESS)
      .filter(( { payload } ) => payload.path === this.path)
      .subscribe(() => {
        this.formGroupDirective.form.reset();
        this.success.emit();
      });

    this.formError = this.actions$
      .ofType(FORM_SUBMIT_ERROR)
      .filter(( { payload } ) => payload.path === this.path)
      .subscribe(( { payload } ) => this.error.emit(payload.error))
  }
}

当然，我们不能忘了清空订阅

connect-form4.directive.ts

ngOnDestroy() {
  this.formChange.unsubscribe();
  this.formError.unsubscribe();
  this.formSuccess.unsubscribe();
}

最后一步就是在有返回的时候调用表单的actions

connect-form4.directive.ts

import {
  formErrorAction,
  formSuccessAction
} from "../connect-form.directive";

@Effect() addStory$ = this.actions$
  .ofType(ADD_STORY)
  .switchMap(action =>
    this.storyService.add(action.payload)
    .switchMap(story => (Observable.from([{
      type: "ADD_STORY_SUCCESS"
    }, formSuccessAction("newStory")])))
    .catch(err => (Observable.of(formErrorAction("newStory", err))))
  )

 

现在我们可以在组件里显示提醒了

ew-story.component.ts

 @Component({
  selector: "new-story-form",
  template: `
    

       ...controls
      Submit
    
    
Success!
    
{{error}}
  `
})
class NewStoryFormComponent {

  constructor(private store: Store ) {}

  onError(error) {
    this.error = error;
  }

  onSuccess() {
    this.success = true;
  }

  submit() {
    // You can also take the payload from the form state in your effect 
    // with the withLatestFrom observable
    this.store.dispatch({
      type: ADD_STORY,
      payload: ...
    })
  }

}