Question

我对angular2很新，我对变化检测有疑问。在加载我的页面时，我需要调用一些API来获取构建我的网页的信息。我所做的是当我收到这些信息（包含在数组中）时，我想使用* ngFor迭代它。这是我的课程组件代码。

import {Component,Input} from 'angular2/core';
import {courseCompDiagram, sepExInWeeks} from "../js/coursesTreatment.js";
import {getSampleWeeks} from "../js/courseMng.js";

@Component({
    selector: 'course',
    directives:[Exercises],
    template: `
    <div class="course">
        <h2>{{aCourse.name}}</h2>
        <div class='diag-container row'> 
            <div id="Completion{{aCourse.name}}"></div>

            <div *ngFor="#week of weeks"> {{week.weekNb}} </div>
        </div>
    </div>`
})

export class Course{
    //This is inputed from a parent component
    @Input() aCourse;
    this.weeks = [];

    ngAfterViewInit(){
        //I call this method and when the callbacks are finished,
        //It does the following lines
        courseCompDiagram(this.aCourse, function(concernedCourse){
            //When my API call is finished, I treat the course, and store the results in weeks
            this.weeks = sepExInWeeks(concernedCourse.course.exercises);
        });
        //This is not supposed to stay in my code,
        //but is here to show that if I call it here,
        //the weeks will effectively change
        this.weeks = getSampleWeeks();
    }


}

首先，我想知道angular2没有检测到this.weeks发生变化的事实是否正常。然后我不知道我是否应该使用ngAfterViewInit函数来完成我的工作。问题是我开始这样做，因为在我的courseCompDiagram中我需要使用jquery来查找包含id {{1并修改它（使用高图表）。但也许我应该在加载页面的其他一些方面做这一切？我尝试使用this主题中所述的ngZone和ChangeDetectionStrategy，但我没有设法让它适用于我的案例。

任何帮助都会受到赞赏，即使它没有完全解决问题。

Answer 1

export class Course{
    //This is inputed from a parent component
    @Input() aCourse;
    this.weeks = [];

    constructor(private _zone:NgZone) {}

    ngAfterViewInit(){
        //I call this method and when the callbacks are finished,
        //It does the following lines
        courseCompDiagram(this.aCourse, (concernedCourse) => {
            //When my API call is finished, I treat the course, and store the results in weeks
            this._zone.run(() => {
              this.weeks = sepExInWeeks(concernedCourse.course.exercises);
            });
        });
        //This is not supposed to stay in my code,
        //but is here to show that if I call it here,
        //the weeks will effectively change
        this.weeks = getSampleWeeks();
    }


}

Answer 2

您应该使用箭头函数来使用词法this，如下所述：

courseCompDiagram(this.aCourse, (concernedCourse) => {
  // When my API call is finished, I treat the course,
  // and store the results in weeks
  this.weeks = sepExInWeeks(concernedCourse.course.exercises);
});

作为原始回调问题，this关键字与您的组件实例不对应。

有关箭头函数词汇的更多提示，请参阅此链接：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions。

否则，我对您的代码有一个示例评论。您应该利用observable进行HTTP调用。就我所见，在你的代码中似乎并非如此......

回调后Angular2变更检测不起作用

2 个答案: