在iOS的开发当中、我们需要对原有的方法进行改进时，我们可以通过重写父类实现。但是，当我们需要在所有的子类都要修改父类方法，如果父类是我们自定义的API当然可以直接修改API，通常需要修改系统API活着三方库，就需要用到runtime时机制进行方法替换活着补救。
本文章以hook原系统的dealloc方法添加一句NSLog来打印当前页面的释放状态
采用category重写 load 方法，导入工程即可实现方法的替换
UIViewController+Swizzled.h
//
// UIViewController+Swizzled.h
// FtxBookViaPhone
//
// Created by Jone on 2017/2/13.
// Copyright © 2017年 FTXJOY. All rights reserved.
//
#import <UIKit/UIKit.h>
@interface UIViewController (Swizzled)
@end
UIViewController+Swizzled.m
//
// UIViewController+Swizzled.m
// FtxBookViaPhone
//
// Created by Jone on 2017/2/13.
// Copyright © 2017年 FTXJOY. All rights reserved.
//
#import "UIViewController+Swizzled.h"
@implementation UIViewController (Swizzled)
+(void)load {
[super load];
__weak typeof(self) weakSelf = self;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class class = [weakSelf class];
Method oldMethod = class_getInstanceMethod(weakSelf, NSSelectorFromString(@"dealloc"));
Method newMethod = class_getInstanceMethod(weakSelf, @selector(swizzledDealloc));
BOOL didAddMethod = class_addMethod(class, NSSelectorFromString(@"dealloc"), method_getImplementation(newMethod), method_getTypeEncoding(newMethod));
if (didAddMethod) {
class_replaceMethod(class, @selector(swizzledDealloc), method_getImplementation(oldMethod), method_getTypeEncoding(oldMethod));
} else {
method_exchangeImplementations(oldMethod, newMethod);
}
});
}
- (void)swizzledDealloc {
NSLog(@"print:dealloc-%@",NSStringFromClass([self class]));
[self swizzledDealloc];
}
@end
