[MacRuby-devel] forwardingTargetForSelector vs. MacRuby 0.4

Clay Bridges diffengr at gmail.com
Sat Aug 15 11:13:42 PDT 2009


Hi all,

I'm using a forwardingTargetForSelector: to create a wrapper class in
ObjC. It seems to work in ObjC, but when I try to use it in MacRuby
0.4, I get an error. As usual, it's likely I'm doing something quite
foolish.

Since it's kind of a complicated setup, rather than trying to describe
code via email, I've created a minimal-ish project in github
containing ObjC and MacRuby code to illustrate the problem. (I say
minimal-ish, since I'm using XCode). It's here:

http://github.com/diffengr/macruby_forwarding_invocation_example

That contains an XCode project and a rakefile. It has the ObjC classes
Candy and CandyWrapper, and they both have the NSString* property
flavor. CandyWrapper declares that property @dynamic, and forwards it
to Candy.

Here's the code that works in ObjC.

  Candy* rootBeerCandy = [[Candy alloc] init];
  rootBeerCandy.flavor = @"Root Beer";

  CandyWrapper* rootBeerWrapper = [[CandyWrapper alloc]
initWithCandy:rootBeerCandy];
  NSLog(@"Candy#flavor \"%@\", Wrapper#flavor \"%@\"", rootBeerCandy.flavor,
          rootBeerWrapper.flavor);

If you load and run the xcode project in this directory, you'll get this output:

  NSLog[...] <CandyWrapper: 0x104fb0> forwarding flavor to <Candy: 0x103380>
  NSLog[...] Candy#flavor "Root Beer", Wrapper#flavor "Root Beer"

Here's that (I think) same code instantiated in MacRuby, from candy_test.rb:

  rootBeerCandy = Candy.alloc.init
  rootBeerCandy.flavor = 'Root Beer'

  rootBeerWrapper = CandyWrapper.alloc.initWithCandy rootBeerCandy
  puts "Candy#flavor #{rootBeerCandy.flavor}, Wrapper#flavor
#{rootBeerWrapper.flavor}"

You can run this with "macrake test" in the project directory, and it
will give (among other things):

  candy_test.rb:7:in `<main>': undefined method `flavor' for
#<CandyWrapper:0x8000aa2a0> (NoMethodError)
  rake aborted!

So, what am I doing wrong?

Thanks,

Clay Bridges


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