详解Angular中的模板语法

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。

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';
  }
}

• 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>

模板变量

• test-template-variables.component.ts

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

  constructor() { }

  ngOnInit() {
  }

  public saveValue(value: string): void {
    console.log(value);
  }
}

• 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>

值绑定、事件绑定、双向绑定

值绑定：[]

• test-value-bind.component.ts

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

  public imgSrc = './assets/imgs/1.jpg';

  constructor() { }

  ngOnInit() {
  }
}

• 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>

事件绑定：()

• test-event-bind-component.ts

@Component({
  selector: 'app-test-event-binding',
  templateUrl: './test-event-binding.component.html',
  styleUrls: ['./test-event-binding.component.css']
})
export class TestEventBindingComponent implements OnInit {

  constructor() { }

  ngOnInit() {
  }

  public btnClick(event: any): void {
    console.log(event + '测试事件绑定！');
  }
}

• test-event-bind.component.html

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    666a865bc6b58bd00bd75fb3013bf55d事件绑定16b28748ea4df4d9c2150843fecfba68
    4707d5d5b651f1cbaed9f4528beadc49
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    16b28748ea4df4d9c2150843fecfba68
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双向绑定：[()]

• test-twoway-binding.component.ts

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

  public fontSizePx = 14;

  constructor() { }

  ngOnInit() {
  }

}

• 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>

• font-resizer.component.ts

@Component({
  selector: 'app-font-resizer',
  templateUrl: './font-resizer.component.html',
  styleUrls: ['./font-resizer.component.css']
})
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);
  }
}

• 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>

内置结构型指令

*ngIf

• test-ng-if.component.ts

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

  isShow = true;

  constructor() { }

  ngOnInit() {
  }
}

• 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>

*ngFor

• test-ng-for.component.ts

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

  races = [
    {name: 'star'},
    {name: 'kevin'},
    {name: 'kent'}
  ];

  constructor() { }

  ngOnInit() {
  }

}

• 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>

ngSwitch

• test-ng-switch.component.ts

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

  status = 1;

  constructor() { }

  ngOnInit() {
  }

}

• 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>

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: 'app-test-ng-class',
  templateUrl: './test-ng-class.component.html',
  styleUrls: ['./test-ng-class.component.scss']
})
export class TestNgClassComponent implements OnInit {
  public currentClasses: {};

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

  constructor() { }

  ngOnInit() {
    this.currentClasses = {
      'saveable': this.canSave,
      'modified': this.isUnchanged,
      'special': this.isSpecial
    };
  }
}

• 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>

• test-ng-class.component.less

.saveable {
    font-size: 18px;
}

.modified {
    font-weight: bold;
}

.special {
    background-color: #ff3300;
}

NgStyle

• test-ng-style.component.ts

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

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

  constructor() { }

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

}

• 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>

NgModel

• test-ng-model.component.ts

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

  name = 'kevin';

  constructor() { }

  ngOnInit() {
  }

}

• 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>

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: 'app-test-pipe',
  templateUrl: './test-pipe.component.html',
  styleUrls: ['./test-pipe.component.css']
})
export class TestPipeComponent implements OnInit {

  currentTime: Date = new Date();
  
  str = 'aaa';

  money = 34.567;


  constructor() {
  }

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

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>

非空断言

• test-not-null-assert.component.ts

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

  public currentValue: any = null;

  constructor() { }

  ngOnInit() {
  }

}

• 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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