Swift - Store Closures in Dictionary

Question

Is it possible to store closures in dictionaries (how we could store ObjC blocks in dictionaries)? Example:

   data = [String:AnyObject]()
   data!["so:c0.onSelection"] = {() in
       Debug.log(.Debug, message: "Hello, World!")
   }

Answer 1

You can, but with some restrictions. First of all, function types don't inherit from AnyObject and don't share a common base class. You can have a dictionary [String: () -> Void] and [String: (String) -> Int], but they can't be stored in the same dictionary.

I also had to use a typealias to define the dictionary so that swift would parse correctly. Here's an example based off of your snippet.

typealias myClosure = () -> Void
var data: [String: myClosure]? = [String: myClosure]()
data!["so:c0.onSelection"] = {() -> Void in
    Debug.log(.Debug, message: "Hello, World!")
}

Answer 2

I have a different approach

I create a "holder" class to hold your closures something like this:

typealias SocialDownloadImageClosure = (image : UIImage?, error: NSError?) -> ()
typealias SocialDownloadInformationClosure = (userInfo : NSDictionary?, error: NSError?) -> ()


private class ClosureHolder
{
 let imageClosure:SocialDownloadImageClosure?
 let infoClosure:SocialDownloadInformationClosure?

 init(infoClosure:SocialDownloadInformationClosure)
 {
    self.infoClosure = infoClosure
 }
 init(imageClosure:SocialDownloadImageClosure)
 {
    self.imageClosure = imageClosure
 }
}

then i make the dictionary like this:

var requests = Dictionary<String,ClosureHolder>()

Now to add a closure to the dictionary just do this:

self.requests["so:c0.onSelection"] = ClosureHolder(completionHandler)