//
//  NSObject+RQSafe.m
//  jiaPei
//
//  Created by 张嵘 on 2019/4/2.
//  Copyright © 2019 JCZ. All rights reserved.
//

#import "NSObject+RQSafe.h"

@implementation NSObject (RQSafe)
+ (void)methodSwizzlingWithOriginalSelector:(SEL)originalSelector bySwizzledSelector:(SEL)swizzledSelector{
	Class class = [self class];
	//原有方法
	Method originalMethod = class_getInstanceMethod(class, originalSelector);
	//替换原有方法的新方法
	Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);
	//先尝试給源SEL添加IMP，这里是为了避免源SEL没有实现IMP的情况
	BOOL didAddMethod = class_addMethod(class,originalSelector,
										method_getImplementation(swizzledMethod),
										method_getTypeEncoding(swizzledMethod));
	if (didAddMethod) {//添加成功：说明源SEL没有实现IMP，将源SEL的IMP替换到交换SEL的IMP
		class_replaceMethod(class,swizzledSelector,
							method_getImplementation(originalMethod),
							method_getTypeEncoding(originalMethod));
	} else {//添加失败：说明源SEL已经有IMP，直接将两个SEL的IMP交换即可
		method_exchangeImplementations(originalMethod, swizzledMethod);
	}
}

@end