Objective-C中的self

它似乎与消息传递一起工作([self sayHi]可以在任何方法中工作).

我不太明白为什么我不能使用self访问对象的私有成员(在下面的示例中,我显示我不能使用self.width)

#import <Foundation/Foundation.h>

// Write an Objective-C class
@interface Rectangle : NSObject
{
  int width ;
}

-(int)getWidth;
-(void)setWidth:(int)w;
-(void)sayHi;
-(void)sayHi:(NSString*)msg ;
@end

@implementation Rectangle

-(int)getWidth
{
  // <b>return self.width ; // ILLEGAL,but why?</b>
  // why can't I return self.width here?
  // why does it think that's a "method"?
  return width ;
}
-(void)setWidth:(int)w
{
  // <b>self.width = w ; // ILLEGAL</b>
  // again here,I CAN'T do self.width = w ;
  width = w ;
}
-(void)sayHi
{
  puts("hi");
}
-(void)sayHi:(NSString*)msg
{
  printf( "Hi,and %sn",[ msg UTF8String ] ) ;
}

@end

int main (int argc,const char * argv[])
{
  NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

  Rectangle* r = [ Rectangle alloc ] ;
  [ r sayHi ] ;
  [ r setWidth:5 ] ;
  printf( "width is %dn",[ r getWidth ] ) ;

  [pool drain];
  return 0;
}