Runtime

1.归档与反归档

#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#import "Dog.h"
@interface Person : NSObject
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) NSString *gender;
@property (nonatomic, strong) NSNumber *age;
@property (nonatomic, assign) NSInteger weight;
@property (nonatomic, strong) Dog *dog;
+ (Person *)personWithName:(NSString *)name gender:(NSString *)gender age:(NSNumber *)age weight:(NSInteger)weight;
- (void)getPersonMessage;
- (void)walkonTheStreet:(NSString *)str;
@end

#import "Person.h"
#import <objc/runtime.h>// 导入<objc/runtime.h>
@interface Person ()<NSCoding>
@end

@implementation Person
- (void)encodeWithCoder:(NSCoder *)aCoder
{
    unsigned int outCount;
    Ivar *ivarList = class_copyIvarList([Person class], &outCount);
    for (NSInteger i = 0; i < outCount; i++) {  // 采用for循环遍历属性,无需一一归档
        const char *cName = ivar_getName(ivarList[i]);
        NSString *name = [NSString stringWithUTF8String:cName];
        [aCoder encodeObject:[self valueForKey:name] forKey:name];
    }   
}
- (instancetype)initWithCoder:(NSCoder *)aDecoder
{
    self = [super init];
    if (self) {
        unsigned int outCount;
        Ivar *ivarList = class_copyIvarList([Person class], &outCount);
        for (NSInteger i = 0; i < outCount; i++) { // 采用for循环遍历属性,无需一一反归档
            const char *cName = ivar_getName(ivarList[i]);
            NSString *name = [NSString stringWithUTF8String:cName];
            [self setValue:[aDecoder decodeObjectForKey:name] forKey:name];
        }
    }
    return  self;
}

如下方法

Ivar *class_copyIvarList(Class cls, unsigned int *outCount)      //获取所有成员变量
 const char *ivar_getName(Ivar v)            //获取某个成员变量的名字
 const char *ivar_getTypeEncoding(Ivar v)   //获取某个成员变量的类型编码
 Ivar class_getInstanceVariable(Class cls, const char *name)    //获取某个类中指定名称的成员变量
 id object_getIvar(id obj, Ivar ivar)    //获取某个对象中的某个成员变量的值
 void object_setIvar(id obj, Ivar ivar, id value)    //设置某个对象的某个成员变量的值
 TypeEncoding：https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html#//apple_ref/doc/uid/TP40008048-CH100-SW1  // 编码形式

打印实例变量

- (NSString *)description
{
    /*
     * class: 要获取的某个类, outCount: 通过这一个函数执行之后会将成员变量的个数赋值到此
     */
    unsigned int outCount;
    Ivar *ivarList = class_copyIvarList([Person class], &outCount);
    for (NSInteger i = 0; i < outCount; i ++) {
//        每次获取一个成员变量
        Ivar ivar = ivarList[i];
//        打印成员变量的名字和类型编码
        NSLog(@"name = %s, type = %s",ivar_getName(ivar), ivar_getTypeEncoding(ivar));
    }
    return nil;
}

2.消息转发

OC的消息发送机制根据方法名来寻找声明完成的实例方法的实现方法，当类中的方法只声明而未实现时，系统会在逐级父类中寻找方法的实现，当父类中均无方法的实现时, 系统会执行以下方法，故可为未实行的方法进行消息转发，添加实现

1    + resolveInstanceMethod:(SEL)sel      // 为一个实例方法动态添加实现
+ resolveClassMethod:(SEL)sel      //   为一个类方法动态添加实现
2     - (id)forwardingTargetForSelector:(SEL)aSelector
//为没有实现的方法指定一个对象
3     - (void)forwardInvocation:(NSInvocation *)anInvocation
//子类重载这个方法为消息指定其他对象

a. 为一个实例方法动态添加实现

+ (BOOL)resolveInstanceMethod:(SEL)sel 
{
   //    将方法转换为字符串
    NSString *selString = NSStringFromSelector(sel);
    if ([selString isEqualToString:@"walkonTheStreet:"]) {
     //   为一个没有实现的方法动态添加实现
        /* cls: 类
         name: 没有实现的方法
         IMP: 要添加的实现
         types: 动态添加的实现的类型编码*/
        class_addMethod(self, @selector(walkonTheStreet:), (IMP)walkFunc, "V@:@");  // void的编码为 V,  SEL的编码为 :
    }
    return [super resolveInstanceMethod:sel];
}

void walkFunc(id self,SEL sel, NSString *str){
    NSLog(@"Person---%s------%@", __func__, str);
}

b. 为没有实现的方法指定一个对象

方式1

- (id)forwardingTargetForSelector:(SEL)aSelector
{
    NSString *selString = NSStringFromSelector(aSelector);
   if ([selString isEqualToString:@"walkonTheStreet:"]) {
       self.dog = [Dog new];
       return self.dog;
   }
    return [super forwardingTargetForSelector:aSelector];
}

方式2

- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    if ([Dog instanceMethodSignatureForSelector:anInvocation.selector]) {
        self.dog = [Dog new];
        [anInvocation invokeWithTarget:self.dog];
    }
}

// 给方法制定一个有效的签名

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
    NSMethodSignature *methodSignature = [super methodSignatureForSelector:aSelector];
    if (!methodSignature) {
        methodSignature = [Dog instanceMethodSignatureForSelector:aSelector];
    }
    return methodSignature;
}

3.给类目添加实例变量

延展可为类添加属性和方法, 但外界不可访问; 类目可为类添加方法，但无法添加实例变量, 采用runtime可为类目添加外界可访问的实例变量

#import <Foundation/Foundation.h>
@interface NSDictionary (Mydict)
@property (nonatomic,strong) NSString *name;
@end

#import "NSDictionary+Mydict.h"
#import <objc/runtime.h>
@implementation NSDictionary (Mydict)

/*
void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)     //为某个类关联某个对象
id objc_getAssociatedObject(id object, const void *key)
//获取到某个类的某个关联对象
void objc_removeAssociatedObjects(id object) //移除已经关联的对象
*/
// 关联后此属性name在外界可以访问，并且通过移除对象方法随时移除
- (void)setName:(NSString *)name
{
//    objc: 要关联的对象  key: 成员变量对应的key值
//    @selector(属性名) value: value
    objc_setAssociatedObject(self, @selector(name), name, OBJC_ASSOCIATION_COPY_NONATOMIC);  // set方法
}

- (NSString *)name
{
    return objc_getAssociatedObject(self, @selector(name));  //get方法
}