Miqdad Ali Miqdad Ali - 6 months ago 428
AngularJS Question

AngularJS abort all pending $http requests on route change

Please go through the code first

app.js

var app = angular.module('Nimbus', ['ngRoute']);


route.js

app.config(function($routeProvider) {
$routeProvider
.when('/login', {
controller: 'LoginController',
templateUrl: 'templates/pages/login.html',
title: 'Login'
})
.when('/home', {
controller: 'HomeController',
templateUrl: 'templates/pages/home.html',
title: 'Dashboard'
})
.when('/stats', {
controller: 'StatsController',
templateUrl: 'templates/pages/stats.html',
title: 'Stats'
})
}).run( function($q, $rootScope, $location, $route, Auth) {
$rootScope.$on( "$routeChangeStart", function(event, next, current) {
console.log("Started");


/* this line not working */
var canceler = $q.defer();
canceler.resolve();

});

$rootScope.$on("$routeChangeSuccess", function(currentRoute, previousRoute){
$rootScope.title = ($route.current.title) ? $route.current.title : 'Welcome';
});
})


home-controller.js

app.controller('HomeController',
function HomeController($scope, API) {
API.all(function(response){
console.log(response);
})
}
)


stats-controller.js

app.controller('StatsController',
function StatsController($scope, API) {
API.all(function(response){
console.log(response);
})
}
)


api.js

app.factory('API', ['$q','$http', function($q, $http) {
return {
all: function(callback) {
var canceler = $q.defer();
var apiurl = 'some_url'
$http.get(apiurl,{timeout: canceler.promise}).success(callback);
}
}
}]);


When I move from home to stats , again API will send http request, I have many http calls like this, I pasted only few lines of code.

What I need is I need to cancel abort all pending http requests on routechangestart or success

Or any other way to implement the same ?

Answer

I put together some conceptual code for this. It might need tweaking to fit your needs. There's a pendingRequests service that has an API for adding, getting and cancelling requests, a httpService that wraps $http and makes sure all requests are tracked.

By leveraging the $http config object (docs) we can get a way to cancel a pending request.

I've made a plnkr, but you're going to need quick fingers to see requests getting cancelled since the test-site I found typically responds within half a second, but you will see in the devtools network tab that requests do get cancelled. In your case, you would obviously trigger the cancelAll() call on the appropriate events from $routeProvider.

The controller is just there to demonstrate the concept.

DEMO

angular.module('app', [])
// This service keeps track of pending requests
.service('pendingRequests', function() {
  var pending = [];
  this.get = function() {
    return pending;
  };
  this.add = function(request) {
    pending.push(request);
  };
  this.remove = function(request) {
    pending = _.filter(pending, function(p) {
      return p.url !== request;
    });
  };
  this.cancelAll = function() {
    angular.forEach(pending, function(p) {
      p.canceller.resolve();
    });
    pending.length = 0;
  };
})
// This service wraps $http to make sure pending requests are tracked 
.service('httpService', ['$http', '$q', 'pendingRequests', function($http, $q, pendingRequests) {
  this.get = function(url) {
    var canceller = $q.defer();
    pendingRequests.add({
      url: url,
      canceller: canceller
    });
    //Request gets cancelled if the timeout-promise is resolved
    var requestPromise = $http.get(url, { timeout: canceller.promise });
    //Once a request has failed or succeeded, remove it from the pending list
    requestPromise.finally(function() {
      pendingRequests.remove(url);
    });
    return requestPromise;
  }
}])
// The controller just helps generate requests and keep a visual track of pending ones
.controller('AppCtrl', ['$scope', 'httpService', 'pendingRequests', function($scope, httpService, pendingRequests) {
  $scope.requests = [];
  $scope.$watch(function() {
    return pendingRequests.get();
  }, function(pending) {
    $scope.requests = pending;
  })

  var counter = 1;
  $scope.addRequests = function() {
    for (var i = 0, l = 9; i < l; i++) {
      httpService.get('https://public.opencpu.org/ocpu/library/?foo=' + counter++);  
    }
  };
  $scope.cancelAll = function() {
    pendingRequests.cancelAll();
  }
}]);