一般情况下，readonly属性的值是无法修改的，但可以通过特殊方式修改。修改本类readonly属性的值或者子类修改父类readonly属性的值，都可通过👇🏻方法实现：

方法一：使用@synthesize实现

在.m文件中加上@synthesize 属性名=_属性名; 就可以把属性的readonly改成readwrite了。

#import "ZWViewController.h"

@interface ZWViewController ()

@property (nonatomic, copy, readonly) NSString *name;

@end

@implementation ZWViewController

@synthesize name = _name;

- (void)viewDidLoad {
    [super viewDidLoad];
    
    _name = @"zwing";
    
    NSLog(@"%p --- %@", _name, _name);
    
    self->_name = @"Mr_Din";

    NSLog(@"%p --- %@", _name, _name);
}

2022-10-28 11:40:32.260188+0800 Go-Goal[6172:2987594] 0x104e525f8 --- zwing
2022-10-28 11:40:32.260436+0800 Go-Goal[6172:2987594] 0x104e52638 --- Mr_Din

方法二：使用kvc实现

#import "ZWViewController.h"

@interface ZWViewController ()

@property (nonatomic, copy, readonly) NSString *name;

@end

@implementation ZWViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    _name = @"zwing";
    
    NSLog(@"%p --- %@", _name, _name);
    
    [self setValue:@"Mr_Din" forKey:NSStringFromSelector(@selector(name))];
    
    NSLog(@"%p --- %@", _name, _name);
}

2022-10-28 11:44:45.911732+0800 Go-Goal[6186:2989794] 0x1069525f8 --- zwing
2022-10-28 11:44:45.912061+0800 Go-Goal[6186:2989794] 0x106952638 --- Mr_Din

若想禁止kvc修改readonly属性的值，则可以在定义readonly属性的类中添加该方法

+ (BOOL)accessInstanceVariablesDirectly {
    return NO;
}