Angular2：组件未更新

Question

我正在为我所做的一些项目构建一个有角度的应用程序。 我有一个详细页面，显示项目的详细信息。

问题：当我转到项目详细信息页面时，一切都正确。 但是，当我切换项目变量 （通过使用页面上的导航）时，依赖项组件不会更新，它们没有获得正确的项目ID。

包含所有组件的projectdetail.html页面：

<div class="container-content" *ngIf="project">
    <div class="projectdetail">
        <div class="thumbnail header">
            <img [src]="project.img" [alt]="project.name" class="projectImage" />
            <div>
                <h2>{{project.name}}</h2>
                <!--The programming component that you can see in the image-->
                <programming-languages [ids]="project.languages"></programming-languages>
            </div>
        </div>
        <div>
            <carousel interval="5000" noWrap="false">
                <slide *ngFor="let slidez of slides; let index=index">
                    <img [src]="slidez.image" class="carouselimg" />
                    <div class="carousel-caption">
                        <h4>Slide {{slidez.id}}</h4>
                        <p>{{slidez.text}}</p>
                    </div>
                </slide>
             </carousel>
        </div>
        <div class="thumbnail detail">
            <p>{{project.description}}</p>
        </div>
    </div>
    <div class="projects hidden-mm hidden-sm hidden-xs">
        <projectsidelist [notShowId]="selectedProjectId"></projectsidelist>
    </div>
</div>

语言组件代码：

import { Component, Input, OnInit } from '@angular/core';

import { ProgrammingLanguagesService } from '../services/programminglanguages.service';
import { ProgrammingLanguage } from '../models/programmingLanguage';

@Component({
    selector: 'programming-languages',
    templateUrl: 'app/components/programminglanguages.component.html',
    providers: [ProgrammingLanguagesService]  
})
export class ProgrammingLanguages implements OnInit {
    @Input()
    ids: number[];
    programmingLanguages: ProgrammingLanguage[];
    constructor(private programmingLanguagesService: ProgrammingLanguagesService) {

    }

    getProgrammingLanguages() {
        this.programmingLanguagesService.getProgrammingLanguages().subscribe(programmingLanguages => {
            var result: ProgrammingLanguage[] = [];
            this.ids.forEach((key: number) => {
                programmingLanguages.forEach((programmingLanguage: ProgrammingLanguage) => {
                    if (programmingLanguage.id == key)
                    {
                        result.push(programmingLanguage);
                    }
                })
            })       
            this.programmingLanguages = result;
        });
    }

    ngOnInit() {
        setTimeout(() => this.getProgrammingLanguages(), 0);
    }
}

编程语言html：

<div class="languageoverlay">
    <span *ngFor="let programmingLanguage of programmingLanguages; let lastElement = last">
        <img [src]="programmingLanguage.img" [alt]="programmingLanguage.name" />
        <span [hidden]="lastElement" class="languageseperator">+</span>
    </span>
</div>

如果您需要额外的代码，请询问或参考github

Github包含所有代码

运行github时的解释：转到http://localhost:3000/#/projectdetail/5 ，然后单击左侧栏上的另一个项目。 然后您看到问题了！

Answer 1

您正确地向组件传递了一个ID数组，但是您从未听过所做的更改，因此可以快速解决该问题：

在programminglanguages.component.ts中更改此代码：

import { Component, Input, OnInit } from '@angular/core';

至

import { Component, Input, OnInit, OnChanges} from '@angular/core';

和

export class ProgrammingLanguages implements OnInit {

至

export class ProgrammingLanguages implements OnInit, OnChanges {

最后将这个生命周期函数添加到您的类主体中：

 ngOnChanges(): void {
        this.getProgrammingLanguages();
    }