iOS 访问和修改类的私有变量

1、使用KVC，新建一个 USer 类

#import "User.h"

@interface User()
{
    NSString *_name;
}

@property (nonatomic, copy) NSString *type;

@end

@implementation User


- (instancetype)init
{
    self = [super init];
    if (self) {
        _name = @"initName";
        self.type = @"initType";
    }
    return self;
}
- (void)before
{
    NSLog(@"修改之前：%@ -- %@",_name,self.type);
}
- (void)after
{
    NSLog(@"修改之后：%@ -- %@",_name,self.type);
}

修改

User *u1 = [[User alloc] init];
[u1 before];
[u1 setValue:@"chen" forKey:@"name"];
[u1 after];

打印结果：
修改之前：initName -- initType
修改之后：chen -- initType
访问的可以使用方法

NSString *name = [u1 valueForKeyPath:@"type"];
NSString *type = [u1 valueForKey:@"name"];

2、使用runtime

    User *u1 = [[User alloc] init];
    [u1 before];
    
    unsigned int count = 0;
    Ivar *ivarList = class_copyIvarList([u1 class], &count);
    for (int i=0; i<count; i++)
    {
        Ivar ivar = ivarList[i];
        const char *privateName = ivar_getName(ivar);
        NSLog(@"%s",privateName);
    }
    
    Ivar name = ivarList[0];
    Ivar type = ivarList[1];
    
    // 访问
    NSLog(@"%@  --  %@",object_getIvar(u1, name),object_getIvar(u1, type));
    object_setIvar(u1, name, @"newName");
    object_setIvar(u1, type, @"newType");
    
    [u1 after];

打印结果

修改之前：initName -- initType
_name
_type
initName  --  initType
修改之后：newName -- newType

修改和访问成功