如何只用ng-container创建一个if-else Angular模板?

时间:2017-05-31 14:44:51

标签: angular if-statement angular-template

我想在我的角度模板中创建一个if-else语句。我从那开始:

<ng-container *ngIf="contributeur.deb; else newDeb" >
    [... HERE IS A RESULT 1]
</ng-container>
<ng-template #newDeb>
    [... HERE IS A RESULT 2]
</ng-template>

我试图只使用ng-container:

<ng-container *ngIf="contributeur.deb; else newDeb" >
    [... HERE IS A RESULT 1]
</ng-container>
<ng-container #newDeb>
    [... HERE IS A RESULT 2]
</ng-container >

不幸的是,这不起作用。我有这个错误:

ERROR TypeError: templateRef.createEmbeddedView is not a function
    at ViewContainerRef_.createEmbeddedView (eval at <anonymous> (vendor.bundle.js:11), <anonymous>:10200:52)
    at NgIf._updateView (eval at <anonymous> (vendor.bundle.js:96), <anonymous>:2013:45)
    at NgIf.set [as ngIfElse] (eval at <anonymous> (vendor.bundle.js:96), <anonymous>:1988:18)
    at updateProp (eval at <anonymous> (vendor.bundle.js:11), <anonymous>:11172:37)
    at checkAndUpdateDirectiveInline (eval at <anonymous> (vendor.bundle.js:11), <anonymous>:10873:19)
    at checkAndUpdateNodeInline (eval at <anonymous> (vendor.bundle.js:11), <anonymous>:12290:17)
    at checkAndUpdateNode (eval at <anonymous> (vendor.bundle.js:11), <anonymous>:12258:16)
    at debugCheckAndUpdateNode (eval at <anonymous> (vendor.bundle.js:11), <anonymous>:12887:59)
    at debugCheckDirectivesFn (eval at <anonymous> (vendor.bundle.js:11), <anonymous>:12828:13)
    at Object.eval [as updateDirectives] (ActionsButtons.html:5)

有人能解释一下这段代码出了什么问题吗?

2 个答案:

答案 0 :(得分:30)

The code for the ngIf directive期望传递对else分支的模板(TemplateRef)的引用,它将调用createEmbeddedView来显示嵌套内容。因此,尝试对else内容使用任何其他类型的元素是没有意义的 - 它只是不起作用。如果需要,您可以在ng-container内嵌入ng-template

这可能看似不直观,但请记住,structural directives(即您使用*调用的那些)总是表示为ng-template下的<ng-container *ngIf="contributeur.deb; else newDeb" > ... </ng-container> <ng-template #newDeb> ... </ng-template> 引擎盖,无论它们附加什么样的元素 - 这两段代码是相同的:

<ng-template [ngIf]="contributeur.deb; else newDeb">
    <ng-container>
        ...
    </ng-container>
</ng-template>
<ng-template #newDeb>
    ...
</ng-template>
git fetch PARENT

答案 1 :(得分:2)

我不喜欢如果不是的标准Angular结构。然后,我找到了 ngSwitch 的替代解决方案:

<ng-container [ngSwitch]="isFirstChoice(foo) ? 1 : (isSecondChoice(foo) ? 2 : -1)">
  <ng-container *ngSwitchCase="1">
    ...first choice...
  </ng-container>
  <ng-container *ngSwitchCase="2">
    ...second choice...
  </ng-container>
  <ng-container *ngSwitchDefault>
    ...another choice...
  </ng-container>
</ng-container>

要回答您的请求,我将使用以下内容:

<ng-container [ngSwitch]="contributeur.deb && 'isDeb'">
  <ng-container *ngSwitchCase="'isDeb'">
    ......
  </ng-container>
  <ng-container *ngSwitchDefault>
    ......
  </ng-container>
</ng-container>