Closures causing error Swift

Question

I have two classes, Model and ViewController. I have called a method in Model from ViewController on completion of which I need to execute the closure. This is What I have done:

Model.swift

typealias LoginCompletionBlock = () -> Void

func registerUser(username : String, emailID email : String, password userPassword : String, profileImage picture : UIImage, registrationMethod method : String, onCompletion completion : LoginCompletionBlock)
{
    //Necessary code for an async request
}

// Delegate for getting the registration details
func registrationSucceededForUser(userID : String, withAccessToken token : String)
{
    LoginCompletionBlock() // Error 'LoginCompletionBlock' is not constructible with '()'
}

And in ViewController.swift, I have called the function like this:

@IBAction func signUp(sender: UIButton)
{
    model.registerUser(usernameTextField.text, emailID: emailTextField.text, password: passwordTextField.text, profileImage: profileImageView.image!, registrationMethod: "normal", onCompletion:{
        () in
        //Perform actions after login
    }) //Error 'Bool' is not a subtype of 'Void'
}

I am just getting started with swift. Can anyone please guide me how to use the closures properly and how can I avoid this error. I need to pass a Bool as a parameter in the closure and no return type. I haven't included the Bool in the code since I was just trying to learn how to use closure.

Rikki Gibson · Accepted Answer · 2014-11-28 04:22:46Z

1

If you need to pass a bool into the closure, you have to change the typealias from () -> Void to Bool -> Void. In addition, your registrationSucceededForUser function will need to be changed so the callback is passed in as a parameter. Right now, you're "invoking" a function signature, not an actual function.

Also, some line breaks in the registerUser function signature will go a long way for readability.

typealias LoginCompletionBlock = Bool -> Void
model.registerUser(usernameTextField.text, emailID: emailTextField.text,
    password: passwordTextField.text, profileImage: profileImageView.image!,
    registrationMethod: "normal", onCompletion: {
         success in
        //Perform actions after login
    })
}

edit: I've added the specific modifications I might make to the code. More information may be needed to actually understand the root of the type error. Note that if the body of your inline closure consists of one statement, it can be inferred to be the return value, and you may need to add newline and an empty return statement to satisfy the Void return type.

edited Nov 28, 2014 at 4:22

answered Nov 28, 2014 at 4:09

Rikki Gibson

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6 Comments

Harikrishnan Over a year ago

Sorry, didn't get you. Can you please show the correct code snippet?

Rikki Gibson Over a year ago

I've added an example. "success" in this case is an argument to the function, implicitly typed as a Bool.

Harikrishnan Over a year ago

Ok, let me try this :)

Harikrishnan Over a year ago

Seems like the error with function call disappeared, but I am still confused about how to invoke the closure on successful registration.

Rikki Gibson Over a year ago

Are you trying to figure out how to implement registrationSucceededForUser? Without knowing much about what's really happening here, I would tend to assume that your LoginCompletionBlock will be called in the background thread with a value indicating whether the login completed successfully. If it does complete successfully, the callback you write should invoke registrationSucceededForUser, which will presumably update your view.

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