iOS MRC下的setter方法实现

写一个setter方法用于完成@property(nontamic,retain)NSString *name;

• (void)setName:(NSString *)name {
  if (_name != name) {
  [_name release];
  _name = [name retain];
  }
  }

写一个setter方法用于完成@property(nontamic,copy)NSString *name. 同上，将retain改为copy.