Googlemaps change custom directives attribute value is not working

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I’m working on google map. I want change the markers set base on dropdown select. But the problem is that the element that I bind is not recoginized by angularjs: the {{markers}} in markers attribute was passed as string… upon inspecting it passed the “{{markers}}” once I removed the {{}} I get error…

<div style="padding-top:100px;padding-left:40;">
   <input type="search" id="search" placeholder="Search" ng-model="mymarks">
  <button class="button" ng-click=""  title="search"> test</button>      
   </div>

   <app-map id="appmap" style="height:700px;margin:0px;"
        center="loc"
        markers="{{mymarks}}"
         zoom=14  >