如何在我的angularjs指令中切换属性的值，如contenteditable？

you see my directive to toggle (true/false) the state of a contenteditable element. If i put the "editable" var into a ng-class, it changes correctly. but i'am not able to change the value of an attribute on click. How can i solve this problem, what i'am missing here?you see my directive to toggle (true/false) the