Use output from services to controllers

Question

I want to result of my $http.get from my service to my controller.

myserviceSample.js

  function messagesService($q,$http){
    var messages;
    $http({
      method: 'GET',
      url: 'http://api.com/feedback/list'
    })
    .then(function success(response){

      messages = response.data;
      console.log(messages);
    },function error(response){
      console.log('error'+ response);
    });
    console.log(messages);

    return {
      loadAllItems : function() {
        return $q.when(messages);
      }
    };
  }

})();

mycontrollerSample.js

  function MessagesController(messagesService) {
    var vm = this;

    vm.messages = [];

    messagesService
      .loadAllItems()
      .then(function(messages) {
        console.log(messages);
        vm.messages = [].concat(messages);
      });
  } 
})();

The above code results gives undefined output. What i miss?

Answer 1

$q.when object does expect promise/object to make it working. In your case you have to pass promise object to $q.when as you are doing $http.get call. Here messages object doesn't hold promise of $http.get, so you could change the implementation of method like below.

Service

function messagesService($q,$http){
    var messages = $http({
      method: 'GET',
      url: 'http://api.com/feedback/list'
    })
    .then(function success(response){
       return response.data;
    },function error(response){
       return $q.reject('Error Occured.');
    });

    return {
      loadAllItems : function() {
        return $q.when(messages);
      }
    };
}

Then controller will resolve that promise & .then will do the trick

function MessagesController(messagesService) {
    var vm = this;
    vm.messages = [];
    messagesService
      .loadAllItems()
      .then(function(messages) {
        console.log(messages);
        vm.messages = [].concat(messages);
      });
} 

Note: Using $q to create a custom promise, is considered as bad pattern when you have $http.get method there(which does return promise itself)

Improved Implementation

function messagesService($q, $http) {
  var messages, getList = function() {
    return $http({
      method: 'GET',
      url: 'http://api.com/feedback/list'
    })
    .then(function success(response) {
      messages = response.data
      return response.data;
    }, function error(response) {
      return $q.reject('Error Occured.');
    });
  };

  return {
    loadAllItems: function() {
      if (!data)
        return getList(); //return promise
      else
        return $q.resolve(messages); //return data
    }
  };
};