表达式中的表达式AngularJS

Question

Is it possible to evaluate an expression within an expression?

For example:

<span ng-bind-template="{{test}}"></span>

Where test is as follows:

$scope.test = '{{a}} is equal to {{b}}';

a and b can be anything, lets assume two integers.

So I want to essentially evaluate it twice.

Maybe I should just create a filter and use $interpolate in there?

Answer 1

You can $compile it manually with:

scope.a = "1";
scope.b = "1";
var element = $compile('{{a}} is equal to {{b}}')(scope);

Answer 2

You have several options. A singular expression can be evaluated using the $parse service. This is something without the mustaches, ie {{ }}. Notice the first call creates a function for the expression, the second call passes an object to evaluate it against:

parseA = $parse('a');
console.log(parseA({ a: 1 })); // 1 

A complex expression can be evaluated using $interpolate . This will parse the code for the mustaches and evaluate the expressions inside them against an object you pass. Again, first call creates the function for interpolation, the second call evaluates it against what you pass in. I believe this is what you are looking for:

interpolate = $interpolate('{{a}} is equal to {{b}}');
console.log(interpolate({ a: 1, b: 2})); // 1 is equal to 2 

Finally, if you want to have a full data-bound segment of code, you use $compile . This will bind a $scope to the element, so it has listeners and participates in digest, etc.

compile = $compile('<div>{{a}}</div>');
scope = $scope.$new();
scope.a = 1; 
compile(scope); // <div>1</div> 

Here is a full working fiddle using all three techniques: http://jsfiddle.net/jeremylikness/CAHKE/