Chaining Promises in Coffeescript

Question

Is there a way to chain Promises together in Coffeescript. For example, consider the following javascript code,

return $.getJSON(\'/api/post.json\')         


        

Answer 1

This is my personal favorite way to write promises, with a little bit extra indentation

doSomething = () -> new RSVP.Promise (resolve, reject) ->
  if 1 is 1
    resolve 'Success'
  else
    reject 'Error'

doSomething()
.then (res) ->
      console.log 'Step 1 Success Handler'

    , (err) ->
      console.log 'Step 1 Error Handler'

.then (res) ->
      console.log 'Step 2 Success Handler'

.then (res) ->
      console.log 'Step 3 Success Handler'

    , (err) ->
      console.log 'Step 3 Error Handler'

Which compiles to:

var doSomething;

doSomething = function() {
  return new RSVP.Promise(function(resolve, reject) {
    if (1 === 1) {
      return resolve('Success');
    } else {
      return reject('Error');
    }
  });
};

doSomething().then(function(res) {
  return console.log('Step 1 Success Handler');
}, function(err) {
  return console.log('Step 1 Error Handler');
}).then(function(res) {
  return console.log('Step 2 Success Handler');
}).then(function(res) {
  return console.log('Step 3 Success Handler');
}, function(err) {
  return console.log('Step 3 Error Handler');
});

There are some instances where this works really well too:

step1Success = (res) -> console.log 'Step 1 Success Handler'
step1Error   = (err) -> console.log 'Step 1 Error Handler'

step2Success = (res) -> console.log 'Step 2 Success Handler'

step3Success = (res) -> console.log 'Step 3 Success Handler'
step3Error   = (err) -> console.log 'Step 3 Error Handler'

doSomething()
  .then(step1Success, step1Error)
  .then(step2Success)
  .then(step3Success, step3Error)

Tested on coffee-script v1.6.3