Swift blocks not working

Question

I\'ve been trying to figure out how to use JavaScriptCore in swift. I\'m running into problems however when I have to deal with blocks as arguments, seems like the block is

Answer 1

It has something to do with how Swift implement closure. You need to use @convention(block) to annotate that the closure is ObjC block. Use unsafeBitCast to force cast it

var block : @convention(block) (NSString!) -> Void = {
   (string : NSString!) -> Void in 
    println("test")
}

ctx.setObject(unsafeBitCast(block, AnyObject.self), forKeyedSubscript: "test")

from REPL

swift
Welcome to Swift!  Type :help for assistance.
  1> import Foundation
  2> var block : @convention(block)(NSString!) -> Void = {(string : NSString!) -> Void in println("test")}
block: @convention(block)(NSString!) -> Void =
  3> var obj: AnyObject = reinterpretCast(block) as AnyObject
obj: __NSMallocBlock__ = {} // familiar block type

Answer 2

I have a working demo at:

• https://github.com/dankogai/swift-jsdemo

And here is the part that implements block registration:

typealias ID = AnyObject!
extension JSContext {
    func fetch(key:NSString)->JSValue {
        return getJSVinJSC(self, key)
    }
    func store(key:NSString, _ val:ID) {
        setJSVinJSC(self, key, val)
    }
    func store(key:NSString, _ blk:()->ID) {
        setB0JSVinJSC(self, key, blk)
    }
    func store(key:NSString, _ blk:(ID)->ID) {
        setB1JSVinJSC(self, key, blk)
    }
    func store(key:NSString, _ blk:(ID,ID)->ID) {
        setB2JSVinJSC(self, key, blk)
    }
}

You need a very small objc code and bridging header to make it work. See the repository for details.