[MacRuby-devel] assign value to identifier in runtime with objc codes

[Laurent Sansonetti]

Hi Linan,

You can't really assign a Ruby local variable from Objective-C, since  
Ruby locals are generally scoped around a particular method, but you  
can assign to an instance variable of a given object, a constant, a  
global variable (or eventually a class variable, but this is evil,  
don't try that). Additionally, you can evaluate a local variable  
assignment of a given Binding object from Objective-C, but this  
becomes hardcore.

A simple example, setting an instance variable of an object created  
from a Ruby class from Objective-C:

$ cat /tmp/t.m
#import <MacRuby/MacRuby.h>

int main(void)
{
     [[MacRuby sharedRuntime] evaluateString:@"class Foo; def foo;  
@foo; end; end"];
     id obj = [NSClassFromString(@"Foo") new];
     NSLog(@"-> %@", [obj performRubySelector:@selector(foo)]);
     [obj performRubySelector:@selector(instance_variable_set:)  
withArguments: @"@foo", @"hello", nil];
     NSLog(@"-> %@", [obj performRubySelector:@selector(foo)]);
     [obj performRubySelector:@selector(instance_variable_set:)  
withArguments: @"@foo", @"world", nil];
     NSLog(@"-> %@", [obj performRubySelector:@selector(foo)]);
}

$ gcc /tmp/t.m -o /tmp/t -fobjc-gc -framework MacRuby -framework  
Foundation

$ /tmp/t
2009-07-26 22:48:29.366 t[53439:903] -> <null>
2009-07-26 22:48:29.368 t[53439:903] -> hello
2009-07-26 22:48:29.369 t[53439:903] -> world

HTH,
Laurent

On Jul 26, 2009, at 5:10 PM, Linan Wang wrote:

> Hi everybody,
> I'm trying to migrate from FScript to MacRuby. The problem I'm  
> facing now is how to assign values to variables in the macruby  
> runtime with objc codes. In Fscript framework, it's fairly  
> straightforward: setObject:forIdentifier call of FSInterpreter.
> I've tried rb_define_varible but it does not work. seems it requires  
> rb_objc_ocval_to_rval function call to convert the objc object to  
> ruby object first. Any help is appreciated. Thanks
>
> -- 
> Best regards
>
> Linan Wang
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