子类如何访问父类的属性

// http://www.iosfly.com/2014/05/14/SubClass-modify-SupClass-Property-Protocol/
// Hacker.m
@interface User () // 在子类的.m中暴露父类的内部结构
@property (nonatomic, strong) NSString *passWord;
@end


@implementation Hacker
- (instancetype)init {
    self = [super init];
    if (self) {
        self.userName = @"JackB";
        self.passWord = @"abc";
    }
    return self;
}
@end