Angularjs how to cancel resource promise when switching routes

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孤街浪徒

I\'m just getting my feet wet with Angularjs. I have an issue which I think has something to do with promises.

Let\'s say I load route \'A\' which makes several ajax

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迷失自我

2020-11-30 05:12

There is a similar question with the answer "How to cancel $resource requests".

While it does not address the question exactly it gives all ingredients to cancel resource request when route is switched:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8" />
  <title>Cancel resource</title>
  <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.3.9/angular.js"></script>
  <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.3.9/angular-resource.js"></script>
  <script>
angular.module("app", ["ngResource"]).
factory(
  "services",
  ["$resource", function($resource)
  {
    function resolveAction(resolve)
    {
      if (this.params)
      {
        this.timeout = this.params.timeout;
        this.params.timeout = null;
      }

      this.then = null;
      resolve(this);
    }

    return $resource(
      "http://md5.jsontest.com/",
      {},
      {
        MD5:
        {
          method: "GET",
          params: { text: null },
          then: resolveAction
        },
      });
  }]).
controller(
  "Test",
  ["services", "$q", "$timeout", function(services, $q, $timeout)
  {
    this.value = "Sample text";
    this.requestTimeout = 100;

    this.call = function()
    {
      var self = this;

      self.result = services.MD5(
      {
        text: self.value,
        timeout: $q(function(resolve)
        {
          $timeout(resolve, self.requestTimeout);
        })
      });
    }
  }]);
  </script>
</head>
<body ng-app="app" ng-controller="Test as test">
  <label>Text: <input type="text" ng-model="test.value" /></label><br/>
  <label>Timeout: <input type="text" ng-model="test.requestTimeout" /></label><br/>
  <input type="button" value="call" ng-click="test.call()"/>
  <div ng-bind="test.result.md5"></div>
</body>
</html>

How it works

$resource merges action definition, request params and data to build a config parameter for an $http request.
a config parameter passed into an $http request is treated as a promise like object, so it may contain then function to initialize config.
action's then function may pass timeout promise from params into the config.

Please look at "Cancel Angularjs resource request" for details.

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难免孤独

2020-11-30 05:13

I cancel the promise with $q.reject(). I think that this way is more simple:

In SitesServices.js:

;(() => {
  app.services('SitesServices', sitesServices)
  sitesServices.$inject = ['$http', '$q']
  function sitesServices($http, $q) {

    var sitesPromise = $q.defer()
    this.getSites = () => {
      var url = 'api/sites'
      sitesPromise.reject()
      sitesPromise = $q.defer()
      $http.get(url)
        .success(sitesPromise.resolve)
        .error(sitesPromise.reject)

      return sitesPromise.promise
    }
  }
})()

In SitesController.js:

;(() => {
  app.controller('SitesController', sitesControler)
  sitesControler.$inject = ['$scope', 'SitesServices']
  function sitesControler($scope, SitesServices) {
    $scope.sites = []

    $scope.getSites = () => {
      SitesServices.getSites().then(sites => {
        $scope.sites = sites
      })
    }
  }
})()

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南方客

2020-11-30 05:14

Take a look at this post

You could do what he is doing and resolve the promise to abort the request on a route change (or state change if using ui router).

It may not be the easiest thing to make happen but seems like it can work.

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醉酒成梦

2020-11-30 05:14

Checking the docs for $resource I found a link to this little beauty. https://docs.angularjs.org/api/ng/service/$http#usage

timeout – {number|Promise} – timeout in milliseconds, or promise that should abort the request when resolved.

I've used it with some success. It go a little something like this.

export default function MyService($q, $http) {
  "ngInject";
  var service = {
    getStuff: getStuff,
  };

  let _cancelGetStuff = angular.noop;

  return service;

  function getStuff(args) {
    _cancelGetStuff(); // cancel any previous request that might be ongoing.

    let canceller = $q( resolve => { _cancelGetStuff = resolve; });

    return $http({
      method: "GET",
      url: <MYURL>
      params: args,
      timeout: canceller
    }).then(successCB, errorCB);

    function successCB (response) {
      return response.data;
    }

    function errorCB (error) {
      return $q.reject(error.data);
    }
  }
}

Keep in mind

This assumes you only want the results from the last request
The canceled requests still call successCB but the response is undefined.
It may also call errorCB, the error.status will be -1 just like if the request timed out.

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夕颜

2020-11-30 05:26

First of all, I decided I needed to use $http since I couldn't find any solution that used $resource, nor could I get it to work on my own.

So here's what my factory turned into, based on @Sid's answer here, using the guide at http://www.bennadel.com/blog/2616-aborting-ajax-requests-using-http-and-angularjs.htm

.factory('AllSites',function($http,$q){

    function getSites(categoryID) {

        // The timeout property of the http request takes a deferred value
        // that will abort the underying AJAX request if / when the deferred
        // value is resolved.
        var deferredAbort  = $q.defer();

        // Initiate the AJAX request.
        var request = $http({
            method: 'get',
            url: 'api/categorySites/'+categoryID,
            timeout: deferredAbort.promise
        });

        // Rather than returning the http-promise object, we want to pipe it
        // through another promise so that we can "unwrap" the response
        // without letting the http-transport mechansim leak out of the
        // service layer.
        var promise = request.then(
            function( response ) {
                return( response.data );
            },
            function() {
                return( $q.reject( 'Something went wrong' ) );
            }
        );

        // Now that we have the promise that we're going to return to the
        // calling context, let's augment it with the abort method. Since
        // the $http service uses a deferred value for the timeout, then
        // all we have to do here is resolve the value and AngularJS will
        // abort the underlying AJAX request.
        promise.abort = function() {
            deferredAbort.resolve();
        };

        // Since we're creating functions and passing them out of scope,
        // we're creating object references that may be hard to garbage
        // collect. As such, we can perform some clean-up once we know
        // that the requests has finished.
        promise.finally(
            function() {
                promise.abort = angular.noop;
                deferredAbort = request = promise = null;
            }
        );

        return( promise );
    }

    // Return the public API.
    return({
        getSites: getSites
    });

});

Then, in my controller (route 'A' from my problem):

var allSitesPromise = AllSites.getSites(categoryID);

$scope.$on('$destroy',function(){
    allSitesPromise.abort();
});

allSitesPromise.then(function(allSites){
    // do stuff here with the result
}

I wish the factory wasn't so messy, but I'll take what I can get. However, now there's a separate, related issue Here where, though the promise was cancelled, the next actions are still delayed. If you have an answer for that, you can post it there.

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