1.导入工作
#import <objc/runtime.h>
#import <objc/message.h>
2.定义runtime函数
1.动态创建一个类,objc_allocateClassPair函数：第一个参数是父类。第三个参数extraBytes通常指定为0，该参数是分配给类和元类对象尾部的索引ivars的字节数。
Class People = objc_allocateClassPair([NSObject class], "Person", 0);
2.添加成员变量,第三个参数，如果变量的类型是指针类型，则传递log2(sizeof(pointer_type))。
class_addIvar(People, "_name", sizeof(NSString *), log2(sizeof(NSString *)), @encode(NSString *));
class_addIvar(People, "_age", sizeof(int), sizeof(int), @encode(int));
3.添加方法
//最后一个参数为"v@:@“, v:返回void, i：int ,f:double, c:unsigned char等等
SEL sel = sel_registerName("method:");
class_addMethod(People, sel, (IMP)introduction, "v@:@");
4.定义introduction 方法
// class_getInstanceVariable获取制定名称的私有变量,kvc取值
void introduction(id self, SEL _cmd, id some) {
NSLog(@"%@,my name is:%@,I'm %@ years old",some,[self valueForKey:@"name"],object_getIvar(self, class_getInstanceVariable([self class], "_age")));
}
5.注册类
objc_registerClassPair(People);
6.创建实例
id peopleInstance = [[People alloc]init];
7.KVC 改变peopleInstance里的实例变量
[peopleInstance setValue:@"Carrot" forKey:@"name"];
8.用object_setIvar为成员变量赋值
//从类中获取到成员变量IVar
Ivar age = class_getInstanceVariable(People, "_age");
//为peopleInstance的成员变量赋值
object_setIvar(peopleInstance, age, @22);
9.调用peopleInstance中的sel的方法
#warning objc_msgSend(peopleInstance, s, @"大家好!");参数过多报错 解决：Build Setting–> Apple LLVM 7.0 – Preprocessing–> Enable Strict Checking of objc_msgSend Calls 改为 NO
((void (*)(id, SEL, id))objc_msgSend)(peopleInstance, sel, @"大家好");
10.销毁
peopleInstance = nil;
objc_disposeClassPair(People);
