Putting a Swift closure in an Objective-C bridgeable dictionary.

closure.m

// In Objective-C

typedef NSArray * (^ArrayReturningBlock)(void);

id BlockFromClosure(ArrayReturningBlock closure)
{
    return [closure copy];
}

void CallBlockFromDictionary(NSDictionary *dictionary)
{
    ArrayReturningBlock block = dictionary[@"block"];
    NSLog(@"block result = %@", block());
}

// In Swift

import Foundation

let closure = { () -> [AnyObject]! in
    let a: [AnyObject] = [1, 2, 3]
    return a
}

let dictionary: [String : AnyObject] = [
    "block": BlockFromClosure(closure)
]

CallBlockFromDictionary(dictionary)