objc重载父类属性

@interface parent : NSObject
@property(strong,nonatomic,readonly) NSString* familyName;
@end

@implementation parent
- (instancetype)init{
    self = [super init];
    if (self) {
    }
    return self;
}

@end


@interface child : parent
@property(strong,nonatomic) NSString* familyName;

@end

@implementation child
//@synthesize familyName = _familyName;

- (instancetype)init{
    self = [super init];
    if (self) {
    }
    return self;
}
//- (void)setFamilyName:(NSString *)familyName{
//    _familyName = familyName;
//}
@end

如上，child重载了父类只读属性familyName，child重载后变成了可读可写权限。然后在调用时如下，会出现崩溃。

 child *c = [[child alloc]init];
    c.familyName = @"fff";
    NSLog(@"%@",c.familyName);

原因是因为familyName在父类只读，所以编译器只自动生成了getter方法。child修改了读写权限后，要手动添加settter才行，并且还有调用@synthesize生成变量。