angularjs - How to watch for a property change in a directive -

i have angular directive (with isolate scope) set this

<div ng="$last" somedirective datajson=mydata myprop="{{ mydata.myspecialprop }}"></div> 

(which gets rendered multiple times because it's inside ng-repeat.)

following instructions of so answer, tried observe myprop changes in directive, however, code inside $scope.watch never runs when property changes (on click event). tried scope.$watch(attrs.myprop, function(a,b){...)and never ran either. how watch change in myprop

myapp.directive('somedirective', function(){    return {       restrict: 'ae',       scope: {          datajson: '=',          myprop: '@       },       link: function(scope, elem, attrs){        scope.$watch(scope.myprop, function(a,b){          if (a != b){               console.log("doesn't called when not equal b");           }else{           }         });      }  }); } 

update: click event changes property handle in controller , i'm guessing isn't reflected in isolate scope directive $watch never getting triggered. there way handle that?

when use interpolation binding (@) cannot use scope.$watch, reserved two-way bindings (=) or internal scope properties.

instead, need use attrs.$observe similar job:

link: function(scope, elem, attrs){    attrs.$observe('myprop', function(newval, oldval) {      // debug purposes      console.log('new', newval, 'old', oldval);      if (newval != oldval){           console.log("doesn't called when newval not equal oldval");       } else {           // ...      }     });  } 

also, everytime myprop change, newval will different oldval, bit weird skip case 1 happen.

note: forgot doublequotes datajson two-way binding: datajson="mydata"