为什么$ scope适用于某些表达式而不适用于其他表达式？

I have this in a controller:

我在控制器中有这个:

$scope.address = new Address();
$scope.hasAddress = $scope.address.street !== undefined && $scope.address.street.length > 0;

And this markup:

这个标记:

<p>{{address.street !== undefined && address.street.length > 0}}</p>
<p>{{hasAddress}}</p>

And then this, indirectly through some includes:

然后,间接通过一些包括:

<input type="text" ... ng-model="address.street" required>

When the input first appears, the street is undefined, so the rendered html says:

当输入首次出现时,街道未定义,因此渲染的html说:

<p>false</p><p>false</p>

as expected. But when I enter characters into the input, the html is rendered as:

正如所料。但是当我在输入中输入字符时,html呈现为:

<p>true</p><p>false</p>

Why doesn't the hasAddress variable update? It's changed indirectly by the address object. Is this a case where I use $scope.$apply()? (and oh no, a new thing where I don't know what the heck I'm doing).

为什么hasAddress变量不更新?它由地址对象间接改变。这是我使用$ scope的情况。$ apply()? (哦,不,我不知道我在做什么的新事物)。

1 个解决方案

#1

That's because nothing in your JS is telling it to update.

那是因为你的JS中没有任何东西告诉它更新。

Add to your input: ng-change="updateVar()", then in your JavaScript:

添加到您的输入:ng-change =“updateVar()”,然后在您的JavaScript中:

$scope.updateVar = function() {
  $scope.hasAddress = $scope.address.street !== undefined && $scope.address.street.length > 0;
}

#1