iOS 多个category同时交换同一个方法

1.问题

问题1:同一个类多个category有相同的方法，是如何执行？有没有例外？

文件顺序

结论: 1.结果会覆盖，后面的会覆盖前面的，最后执行的是2的方法。无论是类方法还是实例方法。后面代码会做验证。 2.每个category的 (void)load方法是独立，都会执行，不会相互覆盖。

问题2:同一个类多个category同时交换一个方法，执行顺序如何？(包括交换后方法同名，交换后方法不同名)

结论: 1.如果交换后方法同名，最后只运行类中的方法 2.如果交换后方法不同名，会倒叙执行文件的方法，如上:先执行2->1->宿主类

2.代码

2.1 RuntimeViewController代码

代码语言：javascript复制

#import "RuntimeViewController.h"
#import "RuntimeViewController ExchangeMethod1.h"
#import "RuntimeViewController ExchangeMethod2.h"

@interface RuntimeViewController ()

@end

@implementation RuntimeViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    [RuntimeViewController runtimeLog];
}

- (void)viewWillAppear:(BOOL)animated{
    [super viewWillAppear:animated];
    NSLog(@"viewWillAppear_原生的");
}

- (void)viewWillDisappear:(BOOL)animated{
    [super viewWillDisappear:animated];
    NSLog(@"viewWillDisappear_原生的");
}

- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    NSLog(@"viewWillDisappear_原生的");
}

  (void)runtimeLog{
    NSLog(@"RuntimeViewController");
}

@end

2.2RuntimeViewController ExchangeMethod1代码

代码语言：javascript复制

#import "RuntimeViewController ExchangeMethod1.h"

@implementation RuntimeViewController (ExchangeMethod1)

  (void)load{
    NSLog(@"RuntimeViewController load1");
    [self exchangeInstanceMethod1:@selector(viewWillAppear:) method2:@selector(wp_viewWillAppear:)];
    [self exchangeInstanceMethod1:@selector(viewWillDisappear:) method2:@selector(wp_viewWillDisappear1:)];
}

  (void)exchangeInstanceMethod1:(SEL)method1 method2:(SEL)method2
{
    method_exchangeImplementations(class_getInstanceMethod(self, method1), class_getInstanceMethod(self, method2));
}
- (void)wp_viewWillAppear:(BOOL)animated{
    NSLog(@"viewWillAppear_ExchangeMethod1");
    [self wp_viewWillAppear:animated];
}

- (void)wp_viewWillDisappear1:(BOOL)animated{
    NSLog(@"viewWillDisappear_ExchangeMethod1");
    [self wp_viewWillDisappear1:animated];
}
//直接覆盖
- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    NSLog(@"viewDidAppear_ExchangeMethod1");
}

  (void)runtimeLog{
    NSLog(@"RuntimeViewController1");
}

@end

2.3RuntimeViewController ExchangeMethod2代码

代码语言：javascript复制

#import "RuntimeViewController ExchangeMethod2.h"

@implementation RuntimeViewController (ExchangeMethod2)

  (void)load{
    NSLog(@"RuntimeViewController load2");
    
    [self exchangeInstanceMethod1:@selector(viewWillAppear:) method2:@selector(wp_viewWillAppear:)];
    [self exchangeInstanceMethod1:@selector(viewWillDisappear:) method2:@selector(wp_viewWillDisappear2:)];
}

  (void)exchangeInstanceMethod1:(SEL)method1 method2:(SEL)method2
{
    method_exchangeImplementations(class_getInstanceMethod(self, method1), class_getInstanceMethod(self, method2));
}
- (void)wp_viewWillAppear:(BOOL)animated{
    NSLog(@"viewWillAppear_ExchangeMethod2");
    [self wp_viewWillAppear:animated];
}

- (void)wp_viewWillDisappear2:(BOOL)animated{
    NSLog(@"viewWillDisappear_ExchangeMethod2");
    [self wp_viewWillDisappear2:animated];
}

//直接覆盖
- (void)viewDidAppear:(BOOL)animated{
    [super viewDidAppear:animated];
    NSLog(@"viewDidAppear_ExchangeMethod2");
}

  (void)runtimeLog{
    NSLog(@"RuntimeViewController2");
}

@end