(Angular2) JSON 数据 (http.get()) 未定义，并且数据不会在组件中更新

Question

My http-data.service 接受 json 作为组件模板中的输出。最初，控制台显示前几个调用是未定义的，并且后续调用已经采用 json，但是如果您检查组件，则组件会显示将数据输出到组件的方法只调用一次，并且由于数据尚未到达，它写入未定义， 但在 json 到来后没有更新。帮忙请理解为什么？谢谢

我的http-data.service：

import {Injectable} from '@angular/core';
import {Http} from '@angular/http';
import {Response} from '@angular/http';
import {Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/map';
@Injectable()
export class HttpService{
constructor(private http: Http) {}
getDataOrganizations(): Observable<any[]>{
return this.http.get('http://localhost:3010/data')
.map((resp:Response)=>{
let dataOrganizations = resp.json().organization;
return dataOrganizations;
});
}
getDataModules(): Observable<any[]> {       
return this.http.get('http://localhost:3010/data')
.map((resp: Response)=> {
let dataModules = resp.json().modules;
return dataModules;
});
}
getDataPresets(): Observable<any[]> {       
return this.http.get('http://localhost:3010/data')
.map((resp: Response)=> {
let dataPresets = resp.json().presets;
return dataPresets;
});
}
getDataModuleItems(): Observable<any[]> {       
return this.http.get('http://localhost:3010/data')
.map((resp: Response)=> {
let dataModuleItems = resp.json().module_items;
return dataModuleItems;
});
}
}

我的data-all.service

import { Injectable, EventEmitter } from '@angular/core';
import {Response} from '@angular/http';
import { ModuleModel } from './model-module';
import { ModuleItemsModel } from './model-module-items';
import data from '../data/data-all';
import { PriceService } from './price.service';
import { HttpService } from './http-data.service';
@Injectable()
export class ModuleDataService {
constructor(private priceService: PriceService, private httpService: HttpService){
this.dataMinMaxSum = {minSum: 0, maxSum: 0}
}
private currentPopupView: EventEmitter<any> = new EventEmitter<any>();
private dataModules: ModuleModel[] = this.getDataModules();
private dataMinMaxSum: {};
private dataCalculateVariationOrg: any[];
private dataChangeExecutor: any[];
subscribe(generatorOrNext?: any, error?: any, complete?: any) {
this.currentPopupView.subscribe(generatorOrNext, error, complete);
}
calculte(){
return this.priceService.getDataPrice();
}
getDataModules(){
this.httpService.getDataModules().subscribe(((modules)=>{this.dataModules = modules; console.log(this.dataModules);}));
console.log('dataModules');
console.log(this.dataModules);
return this.dataModules;
}
---------------------------------------------------------------------------
}

我的left-block.component

import { Component, OnInit} from '@angular/core';
import { ModuleDataService } from '../../service/data-all.service';
import { ModuleModel } from '../../service/model-module';
@Component({
moduleId: module.id,
selector: 'modules-left-block',
templateUrl: './modules-left-block.html',
styleUrls: ['modules-left-block.css']
})
export class ModuleLeft implements OnInit{
modules: ModuleModel[];
constructor(private modulesAll: ModuleDataService){}

ngOnInit(){
this.modules = this.modulesAll.getDataModules();
console.log("view");
console.log(this.modulesAll.getDataModules());
}
onToggle(module: any){
this.modulesAll.toggleModules(module);
}
}

我的left-block.component.html

<div class="modules-all">
<div class="modules-all-title">Все модули</div>
<div class="module-item" *ngFor="let module of modules" [ngClass]="{ 'active': module.completed }" (click)="onToggle(module)">{{module?.title}}</div>
</div>

在组件中，this.modulesAll.getDataModules((方法是为什么它只执行一次而不更新(在控制台中写入=>未定义(，如果有任何想法，写，谢谢。

Answer 1

这种行为是由于.subscribe()方法不等待数据到达，我猜你已经知道这一点。您面临的问题是，您必须.subscribewron 地方的getDataModules()服务。您不应该subscribe到另一个服务中的服务(在本例中为 leat(。将subscribe方法移动到left-block.component，它应该可以工作。

getDataModules() {
this.httpService.getDataModules().subscribe(((modules) => {
this.dataModules = modules;
console.log(this.dataModules);
}));
console.log('dataModules');
console.log(this.dataModules);
return this.dataModules;
}

它应该看起来像这样：

@Component({
moduleId: module.id,
selector: 'modules-left-block',
templateUrl: './modules-left-block.html',
styleUrls: ['modules-left-block.css']
})
export class ModuleLeft implements OnInit {
modules: ModuleModel[] = new ModuleModel();
constructor(private modulesAll: ModuleDataService, private httpService: HttpService) {}
ngOnInit() {
this.getDataModles();
//this.modules = this.modulesAll.getDataModules();
console.log("view");
//console.log(this.modulesAll.getDataModules());
}
onToggle(module: any) {
this.modulesAll.toggleModules(module);
}
getDataModules(): void {
this.httpService.getDataModules().subscribe(((modules) => {
this.modules = modules;
console.log(this.dataModules);
}));
}
}