Swift Passing Closure With Params - ios

Question

Currently I'm passing in a closure as a property on an object that accepts no params and has no return value as follows:
class MyClass {
var myClosureProperty: (() -> ())? {
didSet {
doSomeActionWhenClosureIsSet()
}
}
}
var instanceOfMyClass = MyClass()
instanceOfMyClass.myClosureProperty = {
// do some things here...
}
and so far this is working great. I want to be able to pass in a parameter when setting this closure to be used inside the instance of MyClass. I'm looking for SOMETHING like below, although the syntax I'm sure is incorrect:
class MyClass {
var myClosureProperty: ((newString: String) -> ())? {
didSet {
doSomeActionWhenClosureIsSet(newString)
}
}
func doSomeActionWhenClosureIsSet(stringParam: String) -> () {
// create a button with the stringParam title...
}
}
var instanceOfMyClass = MyClass()
instanceOfMyClass.myClosureProperty = {("Action")
exampleFunction()
}
How would I go about passing in a parameter to this closure that can be used inside of MyClass - i.e. a value that can be used inside the didSet portion of the property itself as in the second example?
EDIT: Here's what ended up working for me:
class MyClass {
var myClosurePropertyWithStringAndAction: (buttonName: String, closure: (() -> ()))? {
didSet {
let buttonTitle = myClosurePropertyWithStringAndAction!.buttonName
createButtonWithButtonTitle(buttonTitle)
}
}
func createButtonWithButtonTitle(buttonTitle: String) -> () {
// here I create a button with the buttonTitle as the title and set
// handleButtonPressed as the action on the button
}
func handleButtonPressed() {
self.myClosurePropertyWithStringAndAction?.closure()
}
}
}
And here is how I call it on the instance:
instaceOfMyClass.myClosurePropertyWithStringAndAction = ("Done", {
// do whatever I need to here
})

Answer 1

Since you are trying to set pass 2 things, a closure AND a button name, you won't be able to do that with a simple setter to the closure.
The constraint you have is that these 2 things are dependent on each other, so you must either set both or none.
First of all, adding newString to your closure isn't doing what you think it does. Its a parameter so you can pass a string to your closure when you call it, it isn't a way to pass in a string when you define the closure.
A "Swift way" to do what you want might be to define it as a tuple. You can name the values inside a tuple so it would work how you want it. Try it like this:
class MyClass {
var stringAndClosure: (buttonName: String,closure: (() -> ()))? {
didSet {
//create button named buttonName
let name = stringAndClosure!.buttonName
}
}
}
let instanceOfMyClass = MyClass()
instanceOfMyClass.stringAndClosure = ("Action",{ exampleFunction() })

Answer 2

You should use the in keyword to pass parameters in a closure
{ (someString: String) -> Bool in
//do something with someString
return true
}

Answer 3

Don't think is possible... You can do like this instead :
class MyClass{
var myClosureProperty: (() -> String)?
{
didSet
{
doSomeActionWhenClosureIsSet(myClosureProperty!())
}
}
func doSomeActionWhenClosureIsSet(stringParam: String) -> ()
{
println("it worked: " + stringParam) // hopefully this would print "it worked: SUCCESS"
}
}