property

@property (nonatomic, strong) NSString *name;
那么其实生成的getter和setter相当于下面这样

• (NSString *)name {
  return _name;
  }

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

@property (nonatomic, copy) NSString *name;
那么其实生成的getter和setter相当于下面这样

• (NSString *)name {
  return [_name copy];
  }

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

直接用 @"xxxx" 的就是常量的