* ngFor:#vs let的含义? [英] *ngFor: meaning of # vs let?

问题描述

Am以angular2开头，遇到了两种不同的语法，但不确定它们的区别-或更确切地说它们是如何工作的.

Am starting out in angular2 and have run into 2 different syntax but am not sure of the difference - or rather how they work.

我看到了:

 <select class="form-control" required
      [(ngModel)]="model.power"
        ngControl="power" #power="ngForm" >
      <option *ngFor="let p of powers" [value]="p">{{p}}</option>
    </select>

但这也可行

<div *ngFor="#game of games" (click)="gotoGame(game)" class="col-1-4">
        <span>{{game.id}}</span>{{game.name}}
        <br> {{game.description}}
        <br> {{game.genre.name}}
  </div>

是另一个的别名吗?一个人比另一个人有什么优势?

is one just an alias of the other? what are the advantages of one over the other?

推荐答案

在beta.17中，语法更改了，只有这种形式才有效

In beta.17 the syntax changed and only this form is valid anymore

<select class="form-control" required
  [(ngModel)]="model.power"
    ngControl="power" #power="ngForm" >
  <option *ngFor="let p of powers" [value]="p">{{p}}</option>
</select>

另请参见 https://github.com/angular/angular/blob/master/CHANGELOG.md#200-beta17-2016-04-28

更改BREAK

引用#...现在始终表示ref-.

BREAKING CHANGES

The reference #... now always means ref-.

之前:

• 在ngFor之外，#...表示引用.
• 在ngFor内，它表示局部变量.

• Outside of ngFor, a #... meant a reference.
• Inside of ngFor, it meant a local variable.

此模式令人困惑.

之后:

• <template #abc>现在定义了对TemplateRef的引用，而不是模板内部使用的输入变量.
• 在声明局部变量的结构指令(例如*ngFor)中，不赞成使用#....请使用let.
• <div *ngFor="#item of items">现在变为<div *ngFor="let item of items">
• var-...已过时.
• 使用#或*ngFor之外的ref-
• 对于ngFor，请使用以下语法:<template ngFor let-... [ngForOf]="...">

• <template #abc> now defines a reference to a TemplateRef, instead of an input variable used inside of the template.
• Inside of structural directives that declare local variables, such as *ngFor, usage of #... is deprecated. Use let instead.
• <div *ngFor="#item of items"> now becomes <div *ngFor="let item of items">
• var-... is deprecated.
• use # or a ref- outside of *ngFor
• for ngFor, use the syntax: <template ngFor let-... [ngForOf]="...">

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