Can ng-show directive be used with a delay

Question

I have a spinner this is shown with ng-show="loading>0"

Is there a way I can display this spinner with a delay (say 1 second)?

I can't use a timeout because with multiple requests de loading counter will get out of sync.

What I need is a delay on the ng-show via css transition or similar

Answer 1

My suspicion is that you are looking for a general purpose spinner that includes a delay. The standard, show after 200ms or something like that.

This is a perfect candidate for a directive, and actually pretty easy to accomplish.

I know this is a long code example, but the primary piece is the directive. It's pretty simple.

Listen to a few scope variables and shows after some configurable delay. If the operation takes longer than the delay, it will just get canceled and never show up.

(function() {
  'use strict';

  function SpinnerDirective($timeout) {
    return {
      restrict: 'E',
      template: '<i class="fa fa-cog fa-spin"></i>',
      scope: {
        show: '=',
        delay: '@'
      },
      link: function(scope, elem, attrs) {
        var showTimer;

        //This is where all the magic happens!
        // Whenever the scope variable updates we simply
        // show if it evaluates to 'true' and hide if 'false'
        scope.$watch('show', function(newVal){
          newVal ? showSpinner() : hideSpinner();
        });
        
        function showSpinner() {
          //If showing is already in progress just wait
          if (showTimer) return;

          //Set up a timeout based on our configured delay to show
          // the element (our spinner)
          showTimer = $timeout(showElement.bind(this, true), getDelay());
        }

        function hideSpinner() {
          //This is important. If the timer is in progress
          // we need to cancel it to ensure everything stays
          // in sync.
          if (showTimer) {
            $timeout.cancel(showTimer);
          }

          showTimer = null;

          showElement(false);
        }

        function showElement(show) {
          show ? elem.css({display:''}) : elem.css({display:'none'});
        }

        function getDelay() {
          var delay = parseInt(scope.delay);

          return angular.isNumber(delay) ? delay : 200;
        }
      }
    };
  }

  function FakeService($timeout) {
    var svc = this,
      numCalls = 0;

    svc.fakeCall = function(delay) {
      numCalls += 1;

      return $timeout(function() {

        return {
          callNumber: numCalls
        };

      }, delay || 50);
    };
  }

  function MainCtrl(fakeService) {
    var vm = this;

    vm.makeCall = function(delay) {
      vm.isBusy = true;
      fakeService.fakeCall(delay)
        .then(function(result) {
          vm.result = result;
        }).finally(function() {
          vm.isBusy = false;
        });
    }
  }

  angular.module('spinner', [])
    .service('fakeService', FakeService)
    .controller('mainCtrl', MainCtrl)
    .directive('spinner', SpinnerDirective);

}());

<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css" rel="stylesheet" />
<link href="//maxcdn.bootstrapcdn.com/font-awesome/4.2.0/css/font-awesome.min.css" rel="stylesheet">
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.3.8/angular.min.js"></script>

<div class="container" ng-app="spinner">
  <div class="row" ng-controller="mainCtrl as ctrl">
    <div class="col-sm-12">
      <h2>{{ctrl.result | json}}
        <spinner show="ctrl.isBusy" delay="200"></spinner>
      </h2>
      <button type="button" 
              class="btn btn-primary" 
              ng-click="ctrl.makeCall(2000)" 
              ng-disabled="ctrl.isBusy">Slow Call
      </button>
      <button type="button" 
              class="btn btn-default" 
              ng-click="ctrl.makeCall()" 
              ng-disabled="ctrl.isBusy">Fast Call
      </button>
    </div>
  </div>
</div>