Swift Blocks Not Working

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 run immed

Solution 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!) -> Voidin 
    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!) -> Voidin println("test")}
block: @convention(block)(NSString!) -> Void =
  3> var obj: AnyObject = reinterpretCast(block) as AnyObject
obj: __NSMallocBlock__ = {} // familiar block type

Solution 2:

I have a working demo at:

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

And here is the part that implements block registration:

typealiasID=AnyObject!
extensionJSContext {
    funcfetch(key:NSString)->JSValue {
        return getJSVinJSC(self, key)
    }
    funcstore(key:NSString, _val:ID) {
        setJSVinJSC(self, key, val)
    }
    funcstore(key:NSString, _blk:()->ID) {
        setB0JSVinJSC(self, key, blk)
    }
    funcstore(key:NSString, _blk:(ID)->ID) {
        setB1JSVinJSC(self, key, blk)
    }
    funcstore(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.