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详解Angular中的模板语法

青灯夜游
发布: 2021-04-23 10:37:21
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本篇文章给大家详细介绍一下Angular中的模板语法。有一定的参考价值,有需要的朋友可以参考一下,希望对大家有所帮助。

详解Angular中的模板语法

相关教程推荐:《angular教程

插值表达式

  • test-interpolation.component.ts
@Component({
  selector: 'app-test-interpolation',
  templateUrl: './test-interpolation.component.html',
  styleUrls: ['./test-interpolation.component.css']
})
export class TestInterpolationComponent implements OnInit {

  title = '插值表达式';

  constructor() { }

  ngOnInit() {
  }

  getValue(): string {
    return '值';
  }
}
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  • test-interpolation.component.html
<div class="panel panel-primary">
  <div class="panel-heading">基插值语法</div>
  <div class="panel-body">
    <h3>
      欢迎来到 {{title}}!
    </h3>
    <h3>2+2 = {{2 + 2}}</h3>
    <h3>调用方法{{getValue()}}</h3>
  </div>
</div>
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模板变量

  • test-template-variables.component.ts
@Component({
  selector: &#39;app-test-template-variables&#39;,
  templateUrl: &#39;./test-template-variables.component.html&#39;,
  styleUrls: [&#39;./test-template-variables.component.css&#39;]
})
export class TestTempRefVarComponent implements OnInit {

  constructor() { }

  ngOnInit() {
  }

  public saveValue(value: string): void {
    console.log(value);
  }
}
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  • test-template-variables.component.html
<div class="panel panel-primary">
  <div class="panel-heading">模板变量</div>
  <div class="panel-body">
    <input #templateInput>
    <p>{{templateInput.value}}</p>
    <button class="btn btn-success" (click)="saveValue(templateInput.value)">局部变量</button>
  </div>
</div>
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值绑定、事件绑定、双向绑定

值绑定:[]

  • test-value-bind.component.ts
@Component({
  selector: &#39;app-test-value-bind&#39;,
  templateUrl: &#39;./test-value-bind.component.html&#39;,
  styleUrls: [&#39;./test-value-bind.component.css&#39;]
})
export class TestValueBindComponent implements OnInit {

  public imgSrc = &#39;./assets/imgs/1.jpg&#39;;

  constructor() { }

  ngOnInit() {
  }
}
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  • test-value-bind.component.html
<div class="panel panel-primary">
  <div class="panel-heading">单向值绑定</div>
  <div class="panel-body">
    <img [src]="imgSrc" />
  </div>
</div>
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事件绑定:()

  • test-event-bind-component.ts
@Component({
  selector: &#39;app-test-event-binding&#39;,
  templateUrl: &#39;./test-event-binding.component.html&#39;,
  styleUrls: [&#39;./test-event-binding.component.css&#39;]
})
export class TestEventBindingComponent implements OnInit {

  constructor() { }

  ngOnInit() {
  }

  public btnClick(event: any): void {
    console.log(event + &#39;测试事件绑定!&#39;);
  }
}
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  • test-event-bind.component.html
<div class="panel panel-primary">
    <div class="panel-heading">事件绑定</div>
    <div class="panel-body">
        <button class="btn btn-success" (click)="btnClick($event)">点击按钮</button>
    </div>
</div>
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双向绑定:[()]

  • test-twoway-binding.component.ts
@Component({
  selector: &#39;app-test-twoway-binding&#39;,
  templateUrl: &#39;./test-twoway-binding.component.html&#39;,
  styleUrls: [&#39;./test-twoway-binding.component.css&#39;]
})
export class TestTwowayBindingComponent implements OnInit {

  public fontSizePx = 14;

  constructor() { }

  ngOnInit() {
  }

}
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  • test-twoway-binding.component.html
<div class="panel panel-primary">
  <div class="panel-heading">双向绑定</div>
  <div class="panel-body">
    <app-font-resizer [(size)]="fontSizePx"></app-font-resizer>
    <div [style.font-size.px]="fontSizePx">Resizable Text</div>
  </div>
</div>
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  • font-resizer.component.ts
@Component({
  selector: &#39;app-font-resizer&#39;,
  templateUrl: &#39;./font-resizer.component.html&#39;,
  styleUrls: [&#39;./font-resizer.component.css&#39;]
})
export class FontResizerComponent implements OnInit {

  @Input()
  size: number | string;

  @Output()
  sizeChange = new EventEmitter<number>();

  constructor() { }

  ngOnInit() {
  }

  decrement(): void {
    this.resize(-1);
  }

  increment(): void {
    this.resize(+1);
  }

  resize(delta: number) {
    this.size = Math.min(40, Math.max(8, +this.size + delta));
    this.sizeChange.emit(this.size);
  }
}
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  • font-resizer.component.html
<div style="border: 2px solid #333">
  <p>这是子组件</p>
  <button (click)="decrement()" title="smaller">-</button>
  <button (click)="increment()" title="bigger">+</button>
  <label [style.font-size.px]="size">FontSize: {{size}}px</label>
</div>
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内置结构型指令

*ngIf

  • test-ng-if.component.ts
@Component({
  selector: &#39;app-test-ng-if&#39;,
  templateUrl: &#39;./test-ng-if.component.html&#39;,
  styleUrls: [&#39;./test-ng-if.component.css&#39;]
})
export class TestNgIfComponent implements OnInit {

  isShow = true;

  constructor() { }

  ngOnInit() {
  }
}
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  • test-ng-if.component.html
<div class="panel panel-primary">
  <div class="panel-heading">*ngIf的用法</div>
  <div class="panel-body">
    <p *ngIf="isShow" style="background-color:#ff3300">显示内容</p>
  </div>
</div>
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*ngFor

  • test-ng-for.component.ts
@Component({
  selector: &#39;app-test-ng-for&#39;,
  templateUrl: &#39;./test-ng-for.component.html&#39;,
  styleUrls: [&#39;./test-ng-for.component.css&#39;]
})
export class TestNgForComponent implements OnInit {

  races = [
    {name: &#39;star&#39;},
    {name: &#39;kevin&#39;},
    {name: &#39;kent&#39;}
  ];

  constructor() { }

  ngOnInit() {
  }

}
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  • test-ng-for.component.html
<div class="panel panel-primary">
  <div class="panel-heading">*ngFor用法</div>
  <div class="panel-body">
    <h3>名字列表</h3>
    <ul>
      <li *ngFor="let name of names;let i=index;">
       {{i}}-{{name.name}}
      </li>
    </ul>
  </div>
</div>
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ngSwitch

  • test-ng-switch.component.ts
@Component({
  selector: &#39;app-test-ng-switch&#39;,
  templateUrl: &#39;./test-ng-switch.component.html&#39;,
  styleUrls: [&#39;./test-ng-switch.component.css&#39;]
})
export class TestNgSwitchComponent implements OnInit {

  status = 1;

  constructor() { }

  ngOnInit() {
  }

}
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  • test-ng-switch.component.html
<div class="panel panel-primary">
  <div class="panel-heading">ngSwitch用法</div>
  <div class="panel-body">
    <div [ngSwitch]="status">
      <p *ngSwitchCase="0">Good</p>
      <p *ngSwitchCase="1">Bad</p>
      <p *ngSwitchDefault>Exception</p>
    </div>
  </div>
</div>
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内置属性型指令

HTML 属性与 DOM 属性关系

  • 少量的 HTML 属性与 DOM 属性之间有着一对一的映射关系, 如 id;
  • 有些 HTML 属性没有对应的 DOM 属性, 如 colspan;
  • 有些 DOM 属性没有对应的 HTML 属性, 如 textContent;
  • 就算名字相同, HTML 属性和 DOM 属性也不是同一样东西;
  • HTML 属性的值指定了初始值, DOM 属性的值表示当前值; HTML 属性的值不可改变, DOM 属性的值可以改变。
  • 模板绑定是通过 DOM 属性和事件来工作的, 而不是 HTML 属性。

注意: 插值表达式与属性绑定是同一个东西, 插值表达式属于 DOM 属性绑定。

NgClass

  • test-ng-class.component.ts
@Component({
  selector: &#39;app-test-ng-class&#39;,
  templateUrl: &#39;./test-ng-class.component.html&#39;,
  styleUrls: [&#39;./test-ng-class.component.scss&#39;]
})
export class TestNgClassComponent implements OnInit {
  public currentClasses: {};

  public canSave = true;
  public isUnchanged = true;
  public isSpecial = true;

  constructor() { }

  ngOnInit() {
    this.currentClasses = {
      &#39;saveable&#39;: this.canSave,
      &#39;modified&#39;: this.isUnchanged,
      &#39;special&#39;: this.isSpecial
    };
  }
}
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  • test-ng-class.component.html
<div class="panel panel-primary">
  <div class="panel-heading">NgClass用法</div>
  <div class="panel-body">
    <div [ngClass]="currentClasses">设置多个样式</div>
    <div [class.modified]=&#39;true&#39;></div>
  </div>
</div>
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  • test-ng-class.component.less
.saveable {
    font-size: 18px;
}

.modified {
    font-weight: bold;
}

.special {
    background-color: #ff3300;
}
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NgStyle

  • test-ng-style.component.ts
@Component({
  selector: &#39;app-test-ng-style&#39;,
  templateUrl: &#39;./test-ng-style.component.html&#39;,
  styleUrls: [&#39;./test-ng-style.component.css&#39;]
})
export class TestNgStyleComponent implements OnInit {

  currentStyles: { };
  canSave = false;
  isUnchanged = false;
  isSpecial = false;

  constructor() { }

  ngOnInit() {
    this.currentStyles = {
      &#39;font-style&#39;: this.canSave ? &#39;italic&#39; : &#39;normal&#39;,
      &#39;font-weight&#39;: !this.isUnchanged ? &#39;bold&#39; : &#39;normal&#39;,
      &#39;font-size&#39;: this.isSpecial ? &#39;36px&#39; : &#39;12px&#39;
    };
  }

}
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  • test-ng-style.component.html
<div class="panel panel-primary">
  <div class="panel-heading">NgStyle用法</div>
  <div class="panel-body">
    <div [ngStyle]="currentStyles">
      用NgStyle批量修改内联样式!
    </div>
    <div [style.font-size]="isSpecial? &#39;36px&#39; : &#39;12px&#39;"></div>
  </div>
</div>
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NgModel

  • test-ng-model.component.ts
@Component({
  selector: &#39;app-test-ng-model&#39;,
  templateUrl: &#39;./test-ng-model.component.html&#39;,
  styleUrls: [&#39;./test-ng-model.component.css&#39;]
})
export class TestNgModelComponent implements OnInit {

  name = &#39;kevin&#39;;

  constructor() { }

  ngOnInit() {
  }

}
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  • test-ng-model.component.html
<div class="panel panel-primary">
    <div class="panel-heading">NgModel的用法</div>
    <div class="panel-body">
        <p class="text-danger">ngModel只能用在表单类的元素上面</p>
        <input type="text" name="name" [(ngModel)]="name">
    </div>
</div>
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小工具

管道

Angular 内置的常用管道:

  • uppercase 与 lowercase

uppercase 将字母转换成大写 {{‘aaa’ | uppercase}}
lowercase 将字母转换成小写 {{‘BBB’ | lowercase}}

  • Date

{{ birthday | date: ‘yyyy-MM-dd HH:mm:ss’}}

  • number

{{ pi | number: ‘2.2-2’}}
2.2-2: 表示是保留 2 位整数和 2 位小数。
2-2: 表示最少 2 位小数,最大 2 位小数。

  • 示例

test-pipe.component.ts

@Component({
  selector: &#39;app-test-pipe&#39;,
  templateUrl: &#39;./test-pipe.component.html&#39;,
  styleUrls: [&#39;./test-pipe.component.css&#39;]
})
export class TestPipeComponent implements OnInit {

  currentTime: Date = new Date();
  
  str = &#39;aaa&#39;;

  money = 34.567;


  constructor() {
  }

  ngOnInit() {
    window.setInterval(
      () => { this.currentTime = new Date() }
      , 1000);
  }
}
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test-pipe.component.html

<div class="panel panel-primary">
    <div class="panel-heading">管道的用法</div>
    <div class="panel-body">
      {{ currentTime | date:&#39;yyyy-MM-dd HH:mm:ss&#39; }}
    </div>
    <div class="panel-body">
      {{ str | uppercase }}
    </div>
    <div class="panel-body">
      {{ money | number: &#39;2.2-2&#39; }}
    </div>
</div>
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非空断言

  • test-not-null-assert.component.ts
@Component({
  selector: &#39;app-test-safe-nav&#39;,
  templateUrl: &#39;./test-not-null-assert.component.html&#39;,
  styleUrls: [&#39;./test-not-null-assert.component.css&#39;]
})
export class TestSafeNavComponent implements OnInit {

  public currentValue: any = null;

  constructor() { }

  ngOnInit() {
  }

}
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  • test-not-null-assert.component.html
<div class="panel panel-primary">
  <div class="panel-heading">安全取值</div>
  <div class="panel-body">
    名字:{{currentValue?.name}}
  </div>
</div>
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