CODEWITHSUNDEEP
angularjspromisedeferred
Mr.Frodo
Mr.Frodo

Reputation: 105

Use promise instead of deferred?

I am using Angular JS in salesforce visualforce page. I wrote this code to fetch some information from server. It is an asynchronous call.

var deferred = $q.defer();
Visualforce.remoting.Manager.invokeAction(  //You can related this with any asynchronous service
        '{!$RemoteAction.somepage.someMethod}',
        param,

    function(result,event){
        if(event.type=='exception'){
            deferred.reject(event.message);
        }
        else{

            deferred.resolve(result);
        }
    }
);

return deferred.promise;

Now someone said to me that "Use promise instead of deferred" (but didn't explain why.) This code is working absolutely fine but it seems like some anti-pattern way of doing this (I'm not sure how but i read it somewhere.). Now i saw many documents and resources and tried to figure out what is the best approach to do this.

Can you please explain why it is not a good approach? Also how can i rewrite this code with best approach?

It would be really helpful if you provide your answers in simple language as i am quite new to Angular also i have been to many links so please don't throw more links to me. Thanks.

Edit 1:

I tried to implement the ES6 implementation but in the .then function when i am simply updating a variable it is not running the digest cycle means changes are not reflecting on the UI but it working perfectly fine with my code and code provided by @smnbbrv. can you please provide why it is happening?

Upvotes: 0

Views: 845

Answers (2)

Tom Edwards
Tom Edwards

Reputation: 124

I think its all down to massive bloated pieces of software trying to shave off loading times, using Promise.resolve() limits your ability to use promises...compared to pushing them all into a promises array and then deferring that.

var service = {
getData:getData
}
return service;

function getData(){
  getDataFromServerFunction
       .$loaded()
       .then(function (data){
          deferred.resolve(data);
  });

  return deferred.promise;
}

Upvotes: 1

smnbbrv
smnbbrv

Reputation: 24541

I don't see anything bad in deferring (as long as this is kinda same promise in the end) however it is not a part of ES6 Promise standard / implementation. That's why at the moment you want to migrate from $q to native promises you won't be easily able to do so.

How to change your function: the very first example from here is fully applicable to your case

return $q(function(resolve, reject) {
   Visualforce.remoting.Manager.invokeAction(  //You can related this with any asynchronous service
          '{!$RemoteAction.somepage.someMethod}',
          param,

      function(result,event){
          if(event.type=='exception'){
             reject(event.message);
          }
          else{

             resolve(result);
          }
      }
);

Upvotes: 1

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