How to return a Promise from a function passed to Deferred.pipe()-CodePudding

The following chain is to be executed sequentially

   $.when()
       .pipe(functionA)
       .pipe(functionB)
       .fail(functionC);

where functionA returns a Promise.

function functionA() {
  return networkCall().then(sideEffectsForSuccess).catch(sideEffectsForFailure);
}

function networkCall() {
  return new Promise(function (resolve, reject) {
    return $.ajax(...);
  });
}

However, this doesn't seem to work, since functionB gets immediately executed without waiting for the Promise returned from functionA to resolve (or fail). The chain works correctly if functionA is changed to

function functionA() {
  return $.ajax(...).pipe(sideEffectsForSuccess, sideEffectsForFailure);
}

Unfortunately, I have to use networkCall. Any ideas how to make this work?

CodePudding user response：

Can you return the promise

function functionA() {
   let callPromise = networkCall();
   callPromise.then(sideEffectsForSuccess).catch(sideEffectsForFailure);
   return callPromise;
}

CodePudding user response：

Your implementation of functionA is wrong.

function networkCall() {
  return new Promise(function (resolve, reject) {
    return $.ajax(...);
  });
}

This returns a promise alright, but it does not return the promise it should return.

function networkCall() {
  return $.ajax(...);
}

$.ajax() already gives you a promise. Return that.