Why I don't like KVC - lets you access private instance variables; breaks OOP encapsulation.

main.m

#include <stdio.h>
#include <Foundation/Foundation.h>

// -----
@interface Foo : NSObject
{
@private
    NSNumber* bar;
}

@end

@implementation Foo

- (id) init
{
    self = [super init];
    if ( self )
    {
        bar = [[NSNumber alloc] initWithInteger: 12];
    }
    return self;
}

@end

// --------


int main (int argc, const char * argv[]) {
    // insert code here...
    printf("Hello, World!\n");
    
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
    
    Foo * foo = [[Foo alloc] init];
    
    NSLog(@"foobar: %@", [foo valueForKey: @"bar"] );
    
    [foo release];
    foo = nil;
    
    [pool release];
    return 0;
}

output

run
[Switching to process 27454]
Running…
Hello, World!
2011-04-24 23:34:24.389 test[27454:a0f] foobar: 12

Well put. Maybe this will be improved in a future version of the runtime!

(I'd also love to see private instance variables leave public interfaces in Apple's frameworks one day; once everyone's switched to 64-bit...)