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在Objective-C中是否有用于实现可变/不可变对象类对的标准模式？我目前有类似以下内容,我根据此链接编写

不可变类:

@interface MyObject : NSObject <NSMutableCopying> {
    NSString *_value;
}

@property (nonatomic, readonly, strong) NSString *value;
- (instancetype)initWithValue:(NSString *)value;

@end

@implementation MyObject
@synthesize value = _value;
- (instancetype)initWithValue:(NSString *)value {
    self = [self init];
    if (self) {
        _value = value;
    }
    return self;
}


- (id)mutableCopyWithZone:(NSZone *)zone {
    return [[MyMutableObject allocWithZone:zone] initWithValue:self.value];
}

@end

可变类:

@interface MyMutableObject : MyObject
@property (nonatomic, readwrite, strong) NSString *value;
@end


@implementation MyMutableObject
@dynamic value;

- (void)setValue:(NSString *)value {
    _value = value; …