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Question

我几天前刚开始角度，并做了英雄之旅应用程序。我正在尝试添加一组步骤，以根据选择的英雄在textarea中显示。如果选择了hero1，它应该显示第1步，当点击“下一步”时，它应该显示第2步。我无法弄清楚如何正确显示它。目前，当我点击下一步时，它会显示“[object Promise]”。任何帮助将不胜感激。

校准detail.component.ts

import { Component, OnInit, Input } from '@angular/core';
import { Headers, Http } from '@angular/http';
import { Hero } from '../hero.class';
import { Step } from '../step.class';
import { ActivatedRoute, Params } from '@angular/router';
import { Location } from '@angular/common';
import { InMemoryDataService } from '../in-memory-data.service';
import { HeroService } from '../hero.service';
import { StepService } from '../step.service';
import { Observable } from 'rxjs/Rx';
import 'rxjs/Rx';

@Component({
moduleId: module.id,
selector: 'app-calibration-detail',
templateUrl: './calibration-detail.component.html',
styleUrls: ['./calibration-detail.component.css']
})

export class CalibrationDetailComponent implements OnInit {

@Input()
hero: Hero;
step: Step;

private mainStepText: String = "Main window text"; //It doesnt want to accept this.hero.id
private statusStepText: String = "Status window text";

constructor(
 private heroService: HeroService,
 private stepService: StepService,
 private route: ActivatedRoute,
 private location: Location,
 private http: Http,
 //private memoryService: InMemoryDataService
) { }


ngOnInit(): void {
 this.route.params
   .switchMap((params: Params) => this.heroService.getHero(+params['id']))
   .subscribe(hero => this.hero = hero);

 this.route.params
   .switchMap((params: Params) => this.stepService.getStep(+params['id']))
   .subscribe(step => this.step = step);
}

goBack(): void {
this.location.back();
}

save(): void {
this.heroService.update(this.hero)
  .then(() => this.goBack());
}
next(): void {
this.mainStepText = this.stepService.getStep(this.step.id).toString();
}
}

steps.components.ts

import { Component, OnInit } from '@angular/core';
import { Step } from '../step.class';
import { StepService } from '../step.service';
import { Router } from '@angular/router';

@Component({
moduleId: module.id,
selector: 'app-steps',
templateUrl: './steps.component.html',
styleUrls: ['./steps.component.css']
})
export class StepsComponent implements OnInit {
steps: Step[];
selectedStep: Step;

constructor(
private router: Router,
private stepService: StepService) 
{ }

getSteps(): void {
this.stepService.getSteps().then(steps => this.steps = steps);
}

ngOnInit(): void {
this.getSteps();
}

onSelect(step: Step): void {
this.selectedStep = step;
}
gotoDetail(): void {
this.router.navigate(['/detail', this.selectedStep.id]);
}
}

step.service.ts

import { Injectable }    from '@angular/core';
import { Headers, Http } from '@angular/http';
import 'rxjs/add/operator/toPromise';
import { Step } from './step.class';

@Injectable()
export class StepService {

private headers = new Headers({'Content-Type': 'application/json'});
private stepsUrl = 'api/steps';  // URL to web api

constructor(private http: Http) { }

getSteps(): Promise<Step[]> {
return this.http.get(this.stepsUrl)
           .toPromise()
           .then(response => response.json().data as Step[])
           .catch(this.handleError);
}

getStep(id: number): Promise<Step> {
const url = `${this.stepsUrl}/${id}`;
return this.http.get(url)
  .toPromise()
  .then(response => response.json().data as Step)
  .catch(this.handleError);
}

private handleError(error: any): Promise<any> {
console.error('An error occurred', error); // for demo purposes only
return Promise.reject(error.message || error);
} 
}

校准细节component.html

<div class="grid grid-pad">
<div class="col-1-2">
<div *ngIf="hero">
  <h2 class="labelName">{{hero.name}} details!</h2>
</div>
<div *ngIf="step">
  <div class="mainWindow">
    <textarea readonly="textareaEdit" ng-model="textareaValue" [(ngModel)]="mainStepText"></textarea>
 </div>
  <div class="status">
    <textarea readonly="textareaEdit2" style="background-color: #7B797B;" ng-model="textareaValue" [(ngModel)]="statusStepText"></textarea>
  </div>
 </div> 
 </div>
 <div class="col-1-2">
  <div class="container">
    <div class="pull-right">
        <button style ="min-height: 70px" (click)="empty1()">Empty</button>
        <button style ="min-height: 70px" (click)="save()">Ok</button>
        <button style ="min-height: 70px" (click)="next()">Next</button>
        <button style ="min-height: 70px" (click)="goBack()">Back</button>
        <button style ="min-height: 70px" (click)="empty3()">Empty</button>
    </div>
  </div>
  </div>
  </div>

Answer 1

问题在于对步骤服务的调用：

this.mainStepText = this.stepService.getStep(this.step.id).toString();

对getStep的调用返回一个Promise对象，当你对它运行.toString（）时，返回“[Object Promise]”。你想要做的是用以下内容替换它：

修改的

this.stepService.getStep(this.step.id).then(data => (this.mainStepText = data.name));

这样，您将处理返回的Promise并将其包含的数据设置为本地变量。