angularjs directive controller function executes many time

问题

In angularjs , I am making a treeview using directive.

return {
        restrict: "E",
        //replace: true,
        scope: {member: '=', ShowDetailsCtrlFunc : '&'},
        template: "<li><span ng-click=ShowDetailsCtrlFunc()>{{member.NodeName}}</span></li>",       
        controller: 'MainCtrl',
        link: linkerfunc        
    }

Things are fine, but i observed that controller function calls multiple times while loading. Would be a great learning if explain me the concept behind this. Or is it possible to handle this and let the function execute only once ? I have created below plunker for same.

plunkr

Thanks

来源：https://stackoverflow.com/questions/48669479/angularjs-directive-controller-function-executes-many-time