Assuming that I have an expression-like string in my scope
$scope.expressionString = 'model.key == "anything"'
You can use
$eval to evaluate your expression , there are two ways to do it in your case
In the controller store the evaluated value of the expression like below
$scope.expressionString = $scope.$eval('model.key == "anything"')
and then in the view simply use it without using $eval in the view