Angular27 指令

1 自定概述

2 自定义指令

　　详情参见《揭秘Angular2》

　　2.1 属性指令

　　　　》工具代码

<div class="panel panel-primary">
  <div class="panel-heading">
    <ng-content select=".heading"></ng-content>
  </div>
  <div class="panel-body">
    <ng-content select=".body"></ng-content>
  </div>
  <div class="panel-footer">
    {{currentDate | date : "yyyy-MM-dd HH:mm:ss"}}
  </div>
</div>

HTML

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

@Component({
  selector: 'panel',
  templateUrl: './panel.component.html',
  styleUrls: ['./panel.component.scss']
})
export class PanelComponent implements OnInit {

  currentDate : Date;

  constructor() { }

  ngOnInit() {
    this.currentDate = new Date();
    setInterval(() => {
      this.currentDate = new Date();
    }, 1000);
  }

}

TS

　　　　》指令代码

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

@Directive({
  selector: '[appMyHighLight]'
})
export class MyHighLightDirective {

  @Input()
  highlightColor : string;

  constructor(
    private _elementRef : ElementRef // 依赖注入：ElementRef对象用来操作DOM节点
  ) { }

  @HostListener("mouseenter") // 监听鼠标移入事件
  onMouseEnter() {
    this.highlight(this.highlightColor);
  }

  @HostListener("mouseleave") // 监听鼠标移除事件
  onmouseleave() {
    this.highlight(null);
  }

  // 利用 ElementRef 修改DOM
  private highlight(color : string) {
    this._elementRef.nativeElement.style.backgroundColor = color;
  }

}

TS

　　　　》应用指令的组件

<panel>
  <div class="heading">
    测试组件01
  </div>
  <div appMyHighLight highlightColor="#ff3300" class="body">
    <p>重庆是个好地方</p>
  </div>
</panel>

HTML

import { Component, OnInit } from '@angular/core';
import { TestService } from '../services/test.service';

@Component({
  selector: 'test01',
  templateUrl: './test01.component.html',
  styleUrls: ['./test01.component.scss']
})
export class Test01Component implements OnInit {


  constructor(
  ) { }

  ngOnInit() {
  }

  onClick() : void {
    // 将对象转化成JSON字符串并存储道浏览器缓存中
    window.localStorage.setItem("user", JSON.stringify({name: "王杨帅", age: 9}));
  }

}

TS

　　2.2 结构性指令

　　　　》指令代码

import { Directive, Input, TemplateRef, ViewContainerRef } from '@angular/core';

@Directive({
  selector: '[appDelay]'
})
export class DelayDirective {

  constructor(
    private templateRef: TemplateRef<any>,
    private viewContainerRef: ViewContainerRef
  ) { }

  @Input() set appDelay(time: number) {
      setTimeout(() => {
          this.viewContainerRef.createEmbeddedView(this.templateRef);
      }, time);
  }

}

TS

　　　　》应用指令的组件

<panel>
  <div class="heading">
    测试组件02
  </div>
  <div class="body">
    <div *ngFor="let item of [1,2,3]">
        <span *appDelay="500 * item">
            第 {{item}} 张卡片
        </span>
    </div>
  </div>
</panel>

HTML

import { Component, OnInit } from '@angular/core';
import { TestService } from '../services/test.service';

@Component({
  selector: 'test02',
  templateUrl: './test02.component.html',
  styleUrls: ['./test02.component.scss']
})
export class Test02Component implements OnInit {

  constructor(
  ) { }

  ngOnInit() {
  }

  onClick() : void {
    // 从浏览器缓存中获取数据【PS: 获取到的是string类型的数据】
    let data = localStorage.getItem("user");
    console.log(data);

    // 将JSON字符串转化成对象
    let json_data = JSON.parse(data);
    
    console.log(json_data.name);
    window.localStorage.removeItem("user");
  }

}

TS