如何在运行时替换Objective-C 2.0类方法实现

@interface MyClass : NSObject

- (void)myMethod;

@end

@implementation MyClass

- (void)myMethod {
    NSLog(@"Original implementation of myMethod");
}

@end

#import <objc/runtime.h>

MyClass *instance = [[MyClass alloc] init];

// 获取方法实例
Method originalMethod = class_getInstanceMethod([MyClass class], @selector(myMethod));

// 获取方法实现
IMP originalImplementation = method_getImplementation(originalMethod);

IMP newImplementation = imp_implementationWithBlock(^{
    NSLog(@"New implementation of myMethod");
    // 调用原始实现
    originalImplementation(instance, @selector(myMethod));
});

method_setImplementation(originalMethod, newImplementation);

[instance myMethod]; // 输出：New implementation of myMethod
                      // 输出：Original implementation of myMethod