CODEWITHSUNDEEP
javascriptangularjs
Summer Developer
Summer Developer

Reputation: 2086

Conditional on Function Evaluation Preempts Promise

I have a question similar to this: How do I wait for a promise to finish before returning the variable of a function?

I have a function pass() that does some form validation. As part of this, it will sometimes open a modal that the user has to close before it returns a value, like so:

if ($scope.model.validation == "No") {
  $scope.modalInstance = $uibModal.open({
    animation: true,
    templateUrl: 'pleaseval.html',
    controller: 'PleaseValCtrl',
    size: 'lg'
  }).closed.then(function() {
    return true;
  });
}

Note that it doesn't return true until the modal closes.

However, I have a conditional based on the function's evaluation 

if(pass(form))
{
//some code here
}
else{
alert("Please fill out all the required information before hitting 'Next'");
}

Because it waits for a promise (the modal to close) it returns false and fires the alert, without waiting for the modal to close and actually firing true.

How do I structure this code so as to not fire the alert while waiting for the modal to close?

Thank you!

Edit: I should note that I can do this:

pass(form).then(function(result){
if(result)
{

The problem with this is that if arguments are passed to pass() that don't necessitate waiting for the modal, I get an undefined promise.

TypeError: Cannot read property 'then' of undefined

Upvotes: 0

Views: 42

Answers (1)

PMV
PMV

Reputation: 2128

Since your edit, it sounds like pass sometimes returns a promise. FYI, in the future, the full code of pass would be helpful, particularly around what it returns - your posted code actually shows nothing about what pass returns, since the "return true" isn't actually what pass itself is returning.

You need to ensure pass always returns a promise in every code path. If the modal isn't necessary, and you have a synchronous return value, make pass return Promise.resolve(true); - that is, the value of true, but wrapped as a promise so the return value of pass is always thenable. That way, the caller of pass doesn't need to know or care whether the operation completed sychronously or asynchronously.

Upvotes: 1

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