Conditional binding with AngularJS, concatenate and bind value if property is not empty

问题

I am new to Angular and am trying to bind a string to a model if the value !== empty. This work for one input, but I would like to combine multiple text inputs into one string.

<input type="text" ng-model="data.source">
<input type="text" ng-model="data.medium">     

<span ng-show="data.source"><h3>{{'additionToSource' + data.source}}</h3></span>
<span ng-show="data.medium"><h3>{{'additionToMedium' + data.medium}}</h3>

回答1:

Live demo here (click).

You could simply add the ng-show or ng-hide directive to the h3 itself if you are wanting to hide the whole element.

Alternatively, you could use ternary in the binding to determine what is bound:

{{foo ? 'some string '+foo : ''}}

Explanation:

foo //if $scope.foo is truthy (not empty)
? 'some string '+foo //bind a string with $scope.foo concatenated to the end
: '' //otherwise, bind in an empty string

For your code, it would be:

<h3>{{data.source ? 'additionToString' + data.source : ''}}</h3>

Based on your comments, you may also be looking to return a binding with a function: Live demo (click).

<input ng-model="foo">

<h3 ng-show="foo">{{bar()}}</h3>
<h3>{{foo ? bar() : ''}}</h3>

JavaScript:

$scope.foo = '';
$scope.bar = function() {
  return 'added value '+$scope.foo;
};

来源：https://stackoverflow.com/questions/21538773/conditional-binding-with-angularjs-concatenate-and-bind-value-if-property-is-no