方法交换
坑点1
例子:
- (void)viewDidLoad {
[super viewDidLoad];
self.dataArray = @[@"Jason",@"Lee",@"LI",@"Hello"];
NSLog(@"%@",[self.dataArray objectAtIndex:4]);
}
很明数组越界报异常,那么就可以利用runtime,进行方法hook
+(void)load{
Method oriMethod = class_getInstanceMethod([self class], @selector(objectAtIndex:));
Method swiMethod = class_getInstanceMethod([self class], @selector(js_objectAtIndex:));
method_exchangeImplementations(oriMethod, swiMethod);
}
-(id)js_objectAtIndex:(NSUInteger)index{
if (index > self.count - 1) {
NSLog(@"数组越界了兄嘚");
return nil;
}
return [self js_objectAtIndex:index];
}
发现还是报错
报错信息
-[__NSArrayI objectAtIndex:]怎么会是他呢,不是NSArray么?因为是类簇的设计,我们将代码进行修改
+(void)load{
Method oriMethod = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(objectAtIndex:));
Method swiMethod = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(js_objectAtIndex:));
method_exchangeImplementations(oriMethod, swiMethod);
}
-(id)js_objectAtIndex:(NSUInteger)index{
if (index > self.count - 1) {
NSLog(@"数组越界了兄嘚");
return nil;
}
return [self js_objectAtIndex:index];
}
这时候发现程序已经不崩溃
交换NSArray、NSMutableArray、NSDictionary、NSMutableDictionary的时候注意类簇的问题：
-
NSArray->__NSArrayI -
NSMutableArray->__NSArrayM -
NSDictionary->__NSDictionaryI -
NSMutableDictionary->__NSDictionaryM
坑点2
按照以上的写法,如果我们手动调用一下load方法会怎么样呢
- (void)viewDidLoad {
[super viewDidLoad];
[NSArray load];
self.dataArray = @[@"Jason",@"Lee",@"LI",@"Hello"];
NSLog(@"%@",[self.dataArray objectAtIndex:4]);
}
发先也会崩溃,因为手动调用load方法又将已经交换过的方法交换了回去,等于啥也没做,调用的还是系统的方法
所以hook的时候要这样写
+(void)load{
//防止一些骚操作,比如手动调用hook方法
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Method oriMethod = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(objectAtIndex:));
Method swiMethod = class_getInstanceMethod(objc_getClass("__NSArrayI"), @selector(js_objectAtIndex:));
method_exchangeImplementations(oriMethod, swiMethod);
});
}
坑点3
子类没有实现,但是父类实现了
@interface Person : NSObject
-(void)method1;
-(void)method2;
@end
@implementation Person
-(void)method1{
NSLog(@"method1");
}
-(void)method2{
NSLog(@"method2");
}
@end
============
student 没有实现任何东西
@interface Student : Person
@end
@implementation Student
@end
现在我们建一个student的分类,hook,交换继承自父类的method1
@implementation Student (JS)
+(void)load{
Method oriMethod = class_getInstanceMethod([self class], @selector(method1));
Method swiMethod = class_getInstanceMethod([self class], @selector(js_method1));
method_exchangeImplementations(oriMethod, swiMethod);
}
-(id)js_method1{
return [self js_method1];
}
@end
然后调用
- (void)viewDidLoad {
[super viewDidLoad];
Student *student = [[Student alloc] init];
[student method1];
Person *p = [Person alloc];
[p method1];
// Do any additional setup after loading the view.
}
发现报错
报错信息
发现把父类的方法也交换了,而父类没有实现
js_method1,所以报错怎么解决呢
- 在子类重写
method1发现一切正常 - 根据第一点的思想,方法交换的时候能不能先尝试给他加一个方法,交换自己的方法不要交换父类的,如果添加成功证明自己没有这个方法,那么直接替换,如果添加不成功证明已经有了该方法可以直接交换
+(void)load{
Method oriMethod = class_getInstanceMethod([self class], @selector(method1));
Method swiMethod = class_getInstanceMethod([self class], @selector(js_method1));
BOOL sucess = class_addMethod([self class], @selector(method1), method_getImplementation(swiMethod), method_getTypeEncoding(oriMethod));
if (sucess) {
class_replaceMethod([self class],@selector(js_method1) ,method_getImplementation(oriMethod) , method_getTypeEncoding(oriMethod));
}else{
method_exchangeImplementations(oriMethod, swiMethod);
}
}
坑点4
父类子类都没有实现
@interface Person : NSObject
@end
@implementation Person
@end
=========
@interface Student : Person
-(void)sayHello;
@end
@implementation Student
@end
这时候我们添加一个判断,判断oriMethod是否存在,如果不存在替换后将swizzledSel赋值一个不做任何事情的空实现,
+(void)load{
Method oriMethod = class_getInstanceMethod([self class], @selector(sayHello));
Method swiMethod = class_getInstanceMethod([self class], @selector(js_method1));
if (!oriMethod) {
class_addMethod([self class], @selector(sayHello), method_getImplementation(swiMethod), method_getTypeEncoding(swiMethod));
method_setImplementation(swiMethod, imp_implementationWithBlock(^(id self,SEL _cmd){}));
}
BOOL sucess = class_addMethod([self class], @selector(sayHello), method_getImplementation(swiMethod), method_getTypeEncoding(swiMethod));
if (sucess) {
class_replaceMethod([self class],@selector(js_method1) ,method_getImplementation(oriMethod) , method_getTypeEncoding(oriMethod));
}else{
method_exchangeImplementations(oriMethod, swiMethod);
}
}
