Swift - How can I pass a function with parameters in parameters of a function?

Question

I know that the title sounds complicated, but the question is not.

I have this Swift code:

class MyClass {
let helloWorld: (check: Bool)->()

init(helloWorld: (check: Bool)->()) {
    self.helloWorld = helloWorld
    }
}

let instanceOfMyClass = MyClass(helloWorld: (check: Bool) -> {

})

This gives me an error. What is the correct syntax for the last instruction?

Thanks!

Antonio · Accepted Answer · 2014-07-13 09:47:26Z

4

You can use this:

let instanceOfMyClass = MyClass(helloWorld: { (check) in println(check) } )

but if the closure is the last argument, you can use the trailing closure syntax, where the closure is written outside of the function (init in your case) parenthesis - which is easier to read:

let instance = MyClass() { (check) in
    println(check)
}

There are other shortcuts to define closures, such as this one:

let instance2 = MyClass() { println($0) }

but I suggest you to read the entire closure chapter in the official swift book.

Note: in my code above replace println(...) with your actual processing

edited Jul 13, 2014 at 9:47

answered Jul 13, 2014 at 9:39

Antonio

72.8k11 gold badges152 silver badges170 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Davide Over a year ago

Thank you! And thanks for the link too. I wasn't able to find it.

Antonio Over a year ago

You're welcome. Glad to know my answer helped you ;-)

newacct Over a year ago

when there are no more parameters after taking out the closure, you can omit the parentheses: MyClass { println($0) }

Collectives™ on Stack Overflow

Swift - How can I pass a function with parameters in parameters of a function?

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related