Angular 6自定义指令在值更改后不更新 [英] Angular 6 custom directive not updating after value change

问题描述

我想制作一个动态菜单，菜单本身具有css类，如果我选中一个复选框，则菜单必须从左向右更改位置.

I want to make a dynamic menu, the menu itself has css class in which if i check a checkbox the menu has to change position from left to right.

现在，该指令有效，但只有一次，当程序加载时，如果我尝试更改程序中的复选框，则不会发生任何事情.

Right now the directive works, but only once, when the program loads, if i try to change the check the checkbox within the program nothing happens.

html:

<div class="wrapper">

        <div class="app-menu" adjustSide side="{{position}}">

            <router-outlet></router-outlet>
        </div>

</div>

我尝试了(side)="position" ， [side] ="position" 和 [(side)] ="position" .

和指令:

  @Input('side') private side:string;


    private el: HTMLInputElement;

    constructor( private renderer: Renderer2, private elementRef: ElementRef ) { 
        this.el = this.elementRef.nativeElement; 
    }

     ngOnChanges(changes: { [propName: string]: SimpleChange }) {

        if (this.side == 'left') {
            this.renderer.addClass(this.el, 'offset-left');
            this.renderer.removeClass(this.el, 'offset-right');
        }else{
            this.renderer.removeClass(this.el, 'offset-left');
            this.renderer.addClass(this.el, 'offset-right');
        }
    }

我仍在学习有角度的知识，因此由于某些原因，我不明白为什么新值似乎没有达到指令，但我不知道为什么.

I'm still learning angular, so for some reason i don't understand why it seems the new value doesn't reach to the directive, but i have no idea why.

我做错了什么?我错过了什么吗?

What i'm doing wrong? did i missed something?

推荐答案

您的代码存在一些问题.

There are a few issues with your code.

只需将 adjustSide 用作 @Input 别名，这样就不必在指令中声明其他属性.

Just use the adjustSide as an @Input alias so that you don't have to declare other properties on your directive.

只需像这样使用它:

<div class="wrapper">
  <div class="app-menu" [adjustSide]="position">
    <router-outlet></router-outlet>
  </div>
</div>

指令应如下所示:

import { Directive, ElementRef, Renderer2, Input, OnChanges } from '@angular/core';

@Directive({
  selector: '[adjustSide]'
})
export class AdjustSizeDirective implements OnChanges {

  @Input('adjustSide') side: string;

  constructor(
    private el: ElementRef,
    private renderer: Renderer2
  ) { }

  ngOnChanges() {

    console.log('Side changed to : ', this.side);

    if (this.side == 'left') {
        this.renderer.addClass(this.el.nativeElement, 'offset-left');
        this.renderer.removeClass(this.el.nativeElement, 'offset-right');
    }
    else{
        this.renderer.removeClass(this.el.nativeElement, 'offset-left');
        this.renderer.addClass(this.el.nativeElement, 'offset-right');
    }
  }

}

如果您查看控制台，将会看到 ngOnChanges 被调用.我已经通过它记录了 this.side 的值.

If you have a look at the console, you'll see the ngOnChanges getting called. I've logged the value of this.side through that.

这是 StackBlitz示例您的情况.

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