獲取ngFor數組的長度後，管道改造

Question

我有以下模板：

<div *ngFor="let item of myArray | customPipe1 | customPipe2; let l = length"> 
    Here is the length of my ngFor : {{l}} 
</div> 

不幸的是長度不ngFor存在。我該如何解決這個問題，以便在我的ngFor中有長度可用？

Answer 1

<div *ngFor="let item of myArray | customPipe1 | customPipe2 as result"> 
    Here is the length of my ngFor : {{result.length}} 
</div> 

也https://angular.io/api/common/NgForOf

Answer 2

看到另一個解決方案可以是以下

<div *ngFor="let item of myArray | customPipe1 | customPipe2; let l = count"> 
    Here is the length of my ngFor : {{l}} 
</div> 

Plunker Example

參見

• https://github.com/angular/angular/blob/master/packages/common/src/directives/ng_for_of.ts#L15-L17

Answer 3

好了，這不是很好的角度DOC文檔，你可以在下面的角源代碼中找到 -

https://github.com/angular/angular/blob/master/packages/common/src/directives/ng_for_of.ts

* ngFor接受計數PARAMS。

constructor(public $implicit: T, public ngForOf: NgIterable<T>, public index: number,public count: number) { 
} 

因此，我們可以得到這樣的計數 -

<div *ngFor="let item of items | pipe; let l = count"> 
<div>{{count}}</div> 
</div>