如何从可观察对象中检索值以用于服务API调用

Question

我有一个使用ngrx-store的Angular应用程序。我为我的功能组件提供了以下文件

<componentname>.actions.ts
<componentname>.effects.ts
<componentname>.model.ts
<componentname>.module.ts
<componentname>.reducer.ts
<componentname>.state.ts
<componentname>.selectors.ts
<componentname>-routing.module.ts

我对Observables和NGRX store都是新手，我需要一些帮助来从store中检索一个值(emailAddress)，以便在服务API调用中使用。在服务方法中，我可以订阅并通过控制台记录值，但是，当进行服务调用时，该值为空，因此我无法获得数据。

如何在订阅emailAddress选择器的同时调用服务API，以确保值存在。存储中的电子邮件地址只在用户登录时存储一次，该值永远不会更改。

我的组件

import { selectStrava } from "@app/strava/strava.selector";
import { selectEmailAddress } from "@app/core/auth/auth.selectors";

@Component({
    selector: "srm-strava",
    templateUrl: "./strava.component.html",
    styleUrls: ["./strava.component.scss"],
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class StravaComponent implements OnInit {
    @Input()
    strava$: Observable<Strava>;


    constructor(private stravaStore: Store<IStravaState>) {
        this.strava$ = this.stravaStore.pipe(select(selectStrava));
        }

    ngOnInit() {
        this.stravaStore.dispatch(new GetStravaAuthorization());
    }
}

我的组件选择器

import { createFeatureSelector, createSelector } from '@ngrx/store';
import * as fromAppStore from "@app/core/auth/auth.reducer";
import { IStravaState } from './strava.state';

export const selectStravaState = createFeatureSelector<IStravaState>('strava');
export const state = createSelector(selectStravaState, (stravaState: IStravaState) => stravaState);
export const selectStrava = createSelector(state, (stravaState: IStravaState) => stravaState.strava);

我的API服务中的方法

constructor(http: HttpClient, notificationService: NotificationService, appState: Store<AppState>) {
        this.http = http;
        this.notificationService = notificationService;
        this.appState = appState;               
    }

    public getStravaAuthorization(): Observable<Strava> {    
        this.emailAddress$ = this.appState.pipe(select(selectEmailAddress));
        //the following outputs to the console OK
        this.emailAddress$.subscribe(res => { console.log(res) });            
        //the email address is blank on the next call
        let getStravaApi = `${AppSettings.CONTACTS_API_HOST}employee/strava?emailaddress=${this.emailAddress$}`;
        return this.http.get<Strava>(getStravaApi).pipe(
            tap(result => console.log('getStravaAccess: executed with email ')),
            map(result => result));            

    };

我的效果如下

@Effect()
    getStravaAuthorization$ = this.actions$.pipe(
        ofType<GetStravaAuthorization>(StravaActionTypes.GetStravaAuthorization), mergeMap(() => this.stravaService.getStravaAuthorization()
            .pipe(map((strava: Strava) => new GetStravaAuthorizationSuccess(strava))))
    );

从存储中检索值的电子邮件地址选择器是

export const selectEmailAddress = createSelector(
    selectAuth, (state: AuthState) => {
        if ((state.userDetails === null || state.userDetails === undefined))
            return "";
        else
            return state.userDetails.email
                ;
    }
);

我的控制台日志如下

console.log output

按照建议将代码从服务移动到组件后，我现在在this.emailAddress$上得到一个错误，指出“无法为'new‘选择重载表达式类型不匹配参数emailAddress应该具有可分配给字符串的类型，但它具有可观察的类型

更新的组件代码

import { Component, ChangeDetectionStrategy, OnInit, Input } from "@angular/core";
import { Observable } from "rxjs";
import { take } from "rxjs/operators";
import { Store, select } from "@ngrx/store";
import { GetStravaAuthorization } from "@app/strava/strava.actions";
import { Strava } from "@app/strava/strava.model";
import { IStravaState } from "@app/strava/strava.state"
import { AuthState } from "@app/core/auth/auth.model.ts";
import { AppState } from "@app/core/core.state.ts"
import { selectStrava } from "@app/strava/strava.selector";
import { selectEmailAddress } from "@app/core/auth/auth.selectors";

@Component({
    selector: "srm-strava",
    templateUrl: "./strava.component.html",
    styleUrls: ["./strava.component.scss"],
    changeDetection: ChangeDetectionStrategy.OnPush
})
export class StravaComponent implements OnInit {
    @Input()
    strava$: Observable<Strava>;
    @Input()
    emailAddress$: Observable<string>;

    constructor(private stravaStore: Store<IStravaState>, private appState: Store<AppState>) {
        this.strava$ = this.stravaStore.pipe(select(selectStrava));
    }

    ngOnInit() {
        this.emailAddress$ = this.appState.pipe(select(selectEmailAddress));
        this.stravaStore.dispatch(new GetStravaAuthorization(this.emailAddress$));
    }
}

更新代码

我的组件

ngOnInit() {
        this.appState
            .pipe(
                select(selectEmailAddress),
                first()
            )
            .subscribe((emailAddress) => {
                this.stravaStore.dispatch(new GetStravaAuthorization(emailAddress)); //dispatch action with the payload containing email address
            });
    }

我的效果

@Effect()

    getStravaAuthorization$ = this.actions$
        .pipe(
            ofType<GetStravaAuthorization>(StravaActionTypes.GetStravaAuthorization),
            mergeMap((action) => {
                // passing the action's payload (email address) below to service

             return this.stravaService.getStravaAuthorization(action.payload);
            },
                map((strava: Strava) => new GetStravaAuthorizationSuccess(strava)))
        );

我的服务

 public getStravaAuthorization(emailAddress): Observable<Strava> {
            let getStravaApi = `${AppSettings.CONTACTS_API_HOST}employee/strava?emailaddress=${emailAddress}`;
            return this.http.get<Strava>(getStravaApi).pipe(
                tap(result => console.log('getStravaAccess: executed with emaiL address ')),
                map(result => result));
        }

行为

export class GetStravaAuthorization implements Action {
    readonly type = StravaActionTypes.GetStravaAuthorization;
    constructor(public payload: string) { }
}

export class GetStravaAuthorizationSuccess implements Action {
    readonly type = StravaActionTypes.GetStravaAuthorizationSuccess;
    constructor(public payload: Strava) { }
}

需要指出的是，EmailAddress不是IStraviaState的一部分

import { Strava } from "@app/strava/strava.model";

export interface IStravaState {
    strava: Strava;
}

export const initialStravaState: IStravaState = {
    strava: null
};
export class Strava {
    stravaAuthorization: StravaAuthorization
}

export class StravaAuthorization {
    entityId: string;
    accessToken: string;
    refreshToken: string;
    isAuthorized: boolean;
}

现在我在更新后的代码中看到了错误

Component error

effect error

Answer 1

在下面的代码行中，您将传递this.emailAddress$，假设它是电子邮件地址的值，而它是一个Observable。这就是它行不通的原因。

let getStravaApi = `${AppSettings.CONTACTS_API_HOST}employee/strava?emailaddress=${this.emailAddress$}`;

我强烈建议您从您的组件传递电子邮件，因为该服务在很大程度上不应该访问商店。如果你仍然想在你的服务中订阅状态，你可以这样做：

public getStravaAuthorization(): Observable<Strava> {    
        return this.appState.pipe(
          select(selectEmailAddress),
          first(), // the subscription is immediately ended after retrieval
          mergeMap((emailAddress) => { // getting email address and chaining observables
            let getStravaApi = `${AppSettings.CONTACTS_API_HOST}employee/strava?emailaddress=${emailAddress}`;
            return this.http.get<Strava>(getStravaApi);

          }),
          tap(result => console.log('getStravaAccess: executed with email ')),
          map(result => result)); // you actually don't need this if you're not modifying result
        );
    };

根据您更新的组件进行回答。

请确保您的操作支持名为payload的参数。例如，类似于：

export class MyAction {
  readonly type = MY_TYPE;
  constructor(public payload: string) {}
}

组件：

export class StravaComponent implements OnInit {
    @Input()
    strava$: Observable<Strava>;
    @Input()
    emailAddress$: Observable<string>;

    constructor(private stravaStore: Store<IStravaState>, private appState: Store<AppState>) {
        this.strava$ = this.stravaStore.pipe(select(selectStrava));
    }

    ngOnInit() {
      this.appState
        .pipe(
           select(selectEmailAddress),
           first()
        )
        .subscribe((emailAddress) => {
          this.stravaStore.dispatch(new GetStravaAuthorization(emailAddress)); //dispatch action with the payload containing email address
        });
    }
}

效果：

  @Effect()
    getStravaAuthorization$ = this.actions$
    .pipe(
        ofType<GetStravaAuthorization>(StravaActionTypes.GetStravaAuthorization),
        mergeMap((action) => {
          // passing the action's payload (email address) below to service
          return this.stravaService.getStravaAuthorization(action.payload);
        },
        map((strava: Strava) => new GetStravaAuthorizationSuccess(strava)))
    );

服务：

public getStravaAuthorization(emailAddress): Observable<Strava> {  
        // assigning the emailAdress to the url's param  
        let getStravaApi = `${AppSettings.CONTACTS_API_HOST}employee/strava?emailaddress=${emailAddress}`;
        return this.http.get<Strava>(getStravaApi).pipe(
            tap(result => console.log('getStravaAccess: executed with email ')),
            map(result => result));            

    };

Answer 2

在构建请求时，您似乎正在尝试将可观察对象用作字符串值。

let getStravaApi = `${AppSettings.CONTACTS_API_HOST}employee/strava?emailaddress=${this.emailAddress$}`;`

有几种方法可以实现这一点，我将分享async/await路线。

您可以通过使用.toPromise()方法将其转换为promise来等待可观察对象的结果。

public async getStravaAuthorization(): Observable<Strava> {
  ...
  const emailAddress = await this.emailAddress$.toPromise();
  ...
}

• toPromise
• async/await

Answer 3

您应该从getStravaAuthorization效果中选择电子邮件地址。因此，您可以从您的组件发送: new GetStravaAuthorization()而不带电子邮件，但当电子邮件不为空或未定义时，效果将从您的选择器获取电子邮件，并将其传递给我们的服务。

       @Effect()
        getStravaAuthorization$ = this.actions$.pipe(
            ofType<GetStravaAuthorization>(StravaActionTypes.GetStravaAuthorization),
                 switchMap(() => this.store.pipe(select(selectEmailAddress))), 
                 filter(Boolean), 
                 mergeMap((email: string) => this.stravaService.getStravaAuthorization(email)
                .pipe(map((strava: Strava) => new GetStravaAuthorizationSuccess(strava))))
    );