lookup-1.m

来自「linux下编程用 编译软件」· M 代码 · 共 55 行

/* { dg-do run { target *-*-darwin* } } */

#include <objc/Object.h>
#include <stdlib.h>

typedef struct MyWidget {
  int a;
} MyWidget;

MyWidget gWidget = { 17 };

@protocol MyProto
- (MyWidget *)widget;
@end

@interface Foo: Object
@end

@interface Bar: Foo <MyProto>
@end

@interface Container: Object
+ (MyWidget *)elementForView:(Foo *)view;
@end

@implementation Foo
@end

@implementation Bar
- (MyWidget *)widget {
  return &gWidget;
}
@end

@implementation Container
+ (MyWidget *)elementForView:(Foo *)view
{
  MyWidget *widget = nil;
  if ([view conformsTo:@protocol(MyProto)]) {
    widget = [(Foo <MyProto> *)view widget];
  }
  return widget;
}
@end

int main(void) {
  id view = [Bar new];
  MyWidget *w = [Container elementForView: view];

  if (!w || w->a != 17)
    abort ();

  return 0;
}