Angular 2显示和隐藏元素 [英] Angular 2 Show and Hide an element

问题描述

我在Angular 2中隐藏和显示依赖于布尔变量的元素时遇到问题.

I'm having a problem hiding and showing an element depending of a boolean variable in Angular 2.

这是div显示和隐藏的代码:

this is the code for the div to show and hide:

<div *ngIf="edited==true" class="alert alert-success alert-dismissible fade in" role="alert">
        <strong>List Saved!</strong> Your changes has been saved.
</div>

该变量已被编辑"，并存储在我的组件中:

the variable is "edited" and it's stored in my component:

export class AppComponent implements OnInit{

  (...)
  public edited = false;
  (...)
  saveTodos(): void {
   //show box msg
   this.edited = true;
   //wait 3 Seconds and hide
   setTimeout(function() {
       this.edited = false;
       console.log(this.edited);
   }, 3000);
  }
}

元素是隐藏的，当saveTodos函数启动时，将显示该元素，但是3秒钟后，即使变量返回为false，该元素也不会隐藏.为什么?

The element is hidden, when saveTodos function starts, the element is shown, but after 3 seconds, even if the variable come back to be false, the element does not hide. Why?

推荐答案

您应使用* ngIf指令

You should use the *ngIf Directive

<div *ngIf="edited" class="alert alert-success box-msg" role="alert">
        <strong>List Saved!</strong> Your changes has been saved.
</div>


export class AppComponent implements OnInit{

  (...)
  public edited = false;
  (...)
  saveTodos(): void {
   //show box msg
   this.edited = true;
   //wait 3 Seconds and hide
   setTimeout(function() {
       this.edited = false;
       console.log(this.edited);
   }.bind(this), 3000);
  }
}

---

更新:在Timeout回调内部时，缺少对外部作用域的引用.

---

Update: you are missing the reference to the outer scope when you are inside the Timeout callback.

所以像我在上面添加的那样添加.bind(this)

so add the .bind(this) like I added Above

Q:已编辑是全局变量.您在* ngFor循环中的处理方式是什么? –布劳恩

Q : edited is a global variable. What would be your approach within a *ngFor-loop? – Blauhirn

A:我会将edit作为属性添加到要迭代的对象上.

A : I would add edit as a property to the object I am iterating over.

<div *ngFor="let obj of listOfObjects" *ngIf="obj.edited" class="alert alert-success box-msg" role="alert">
        <strong>List Saved!</strong> Your changes has been saved.
</div>


export class AppComponent implements OnInit{
   
  public listOfObjects = [
    {
       name : 'obj - 1',
       edit : false
    },
    {
       name : 'obj - 2',
       edit : false
    },
    {
       name : 'obj - 2',
       edit : false
    } 
  ];
  saveTodos(): void {
   //show box msg
   this.edited = true;
   //wait 3 Seconds and hide
   setTimeout(function() {
       this.edited = false;
       console.log(this.edited);
   }.bind(this), 3000);
  }
}

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