1. 交換方法

1.1 獲取類方法

Method class_getClassMethod(Class cls , SEL name)

1.2 獲取實(shí)例方法

Method class_getInstanceMethod(Class cls , SEL name)

1.3 交換兩個(gè)方法

void method_exchangeImplementations(Method m1 , Method m2)

實(shí)例：

//Person.h
#import <Foundation/Foundation.h>

@interface Person : NSObject

+ (void)method_1;

+ (void)method_2;

- (void)method_3;

- (void)method_4;

@end

//Person.m
#import "Person.h"

@implementation Person

+ (void)method_1
{
    NSLog(@"method_1");
}

+ (void)method_2
{
    NSLog(@"method_2");
}

- (void)method_3
{
    NSLog(@"method_3");
}

- (void)method_4
{
    NSLog(@"emthod_4");
}

@end


        [Person method_1]; //log: method_1
        [Person method_2];  //log: method_2
        
        Method m1 = class_getClassMethod([Person class], @selector(method_1));
        Method m2 = class_getClassMethod([Person class], @selector(method_2));
        method_exchangeImplementations(m1, m2);
        
        [Person method_1]; //log: method_2
        [Person method_2]; //log: method_1
        
        Person *p = [[Person alloc] init];
        [p method_3];   //log: method_3
        [p method_4];   //log: method_4
        
        Method m3 = class_getInstanceMethod([Person class], @selector(method_3));
        Method m4 = class_getInstanceMethod([Person class], @selector(method_4));
        method_exchangeImplementations(m3, m4);
        
        [p method_3];   //log: method_4
        [p method_4];   //log: method_3

2. 分類添加屬性

下面給NSObject添加一個(gè)name屬性

#import <Foundation/Foundation.h>

@interface NSObject (Category)


@property (nonatomic, strong)   NSString *name;

@end


#import "NSObject+Category.h"
#import <objc/runtime.h>

const char * str = "myKey";


@implementation NSObject (Category)

- (void)setName:(NSString *)name
{
    /**
     *  void objc_setAssociatedObject(id object , const void *key ,id value ,objc_AssociationPolicy policy)
     *  object  需要添加屬性的對(duì)象
     *  key     屬性的key, 將來(lái)可以通過key取出這個(gè)存儲(chǔ)的值
     *  value   屬性的值
     *  policy  使用的策略，是一個(gè)枚舉值僵缺，可根據(jù)開發(fā)需要選擇不同的枚舉
     */
    objc_setAssociatedObject(self, &str, name, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSString *)name
{
    return objc_getAssociatedObject(self, &str);
}

@end

3. 消息攔截轉(zhuǎn)發(fā)

用到的幾個(gè)方法

+ (BOOL)resolveInstanceMethod:(SEL)sel
+ (BOOL)resolveClassMethod:(SEL)sel
- (id)forwardingTargetForSelector:(SEL)aSelector
- (void)forwardInvocation:(NSInvocation *)anInvocation

//對(duì)當(dāng)前類添加一個(gè)newTestMethod方法, 當(dāng)testMethod沒有實(shí)現(xiàn)時(shí), runtime會(huì)進(jìn)行消息轉(zhuǎn)發(fā)
+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    // 指定對(duì)某一個(gè)方法的動(dòng)態(tài)解析
    NSString *selName = NSStringFromSelector(sel);
    if ([selName isEqualToString:@"testMethod"]) {
        // 動(dòng)態(tài)的添加一個(gè)方法
        class_addMethod([self class], @selector(testMethod), (IMP)newTestMethod, "v@:");
        return YES;
    }
    return NO;
}

void newTestMethod()
{
    NSLog(@"%s", __func__);
}

3.2 消息轉(zhuǎn)發(fā)到其他類

// 我們首先要通過, 指定方法簽名，若返回nil皿淋，則表示不處理谬盐。
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
    NSLog(@"指定方法簽名");
    NSString *selName = NSStringFromSelector(aSelector);
    if ([selName isEqualToString:@"testMethod"]) {
        
        return [NSMethodSignature signatureWithObjCTypes:"v@:"];
    }
    
    return [super methodSignatureForSelector:aSelector];
}

// 通過anInvocation對(duì)象做很多處理程剥，比如修改實(shí)現(xiàn)方法变过，修改響應(yīng)對(duì)象等
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    NSLog(@"%s", __func__);
    // 改變響應(yīng)對(duì)象并改變響應(yīng)方法
    [anInvocation setSelector:@selector(newTestMethod)];
    [anInvocation invokeWithTarget:[ZYChildren new]];
}

//跳轉(zhuǎn)到其他類中執(zhí)行
- (id)forwardingTargetForSelector:(SEL)aSelector
 {
     NSLog(@"備用接收者");
 // 指定對(duì)某一個(gè)對(duì)象來(lái)執(zhí)行方法
     NSString *selName = NSStringFromSelector(aSelector);
     if ([selName isEqualToString:@"testMethod"]) {
 
         return [ZYChildren new];
     }
     return [super forwardingTargetForSelector:aSelector];;
 }

        //攔截調(diào)用
        MyClass *myClass = [[MyClass alloc] init];
        [myClass performSelector: @selector(testMethod) withObject: @"test"];

4. 其他用法

 unsigned int count;
         //獲取屬性列表
        objc_property_t *propertyList = class_copyPropertyList([MyClass class], &count);
        for (unsigned int i = 0; i < count; i ++)
        {
            const char *propertyName = property_getName(propertyList[i]);
            NSLog(@"property ----> %@", [NSString stringWithUTF8String: propertyName]);
        }
    
         //獲取實(shí)例方法列表
        Method *methodList = class_copyMethodList([MyClass class], &count);
        for (unsigned int i = 0; i < count; i ++)
        {
            Method method = methodList[i];
            NSLog(@"method ----> %@", NSStringFromSelector(method_getName(method)));
        }
         
    
        //獲取成員變量列表
        Ivar *ivarList = class_copyIvarList([MyClass class], &count);
        for (unsigned int i = 0; i < count; i ++)
        {
            Ivar myIvar = ivarList[i];
            const char *ivarName = ivar_getName(myIvar);
            NSLog(@"Ivar ----> %@", [NSString stringWithUTF8String: ivarName]);
        }
         
        
        //獲取協(xié)議列表
        __unsafe_unretained Protocol **protocolList = class_copyProtocolList([MyClass class], &count);
        for (unsigned int i = 0; i < count; i ++)
        {
            Protocol *myProtocal = protocolList[i];
            const char *protocolName = protocol_getName(myProtocal);
            NSLog(@"protocol ----> %@", [NSString stringWithUTF8String: protocolName]);
        }