【Objective-C Runtime动态加载】---动态创建

动态创建类Class,动态添加Class成员变量与成员函数,动态变量赋值与取值，动态函数调用等方法

a.使用objc_allocateClassPair创建一个类Class

const char * className = "Calculator";
  Class kclass = objc_getClass(className);
  if (!kclass) 
  {
     Class superClass = [NSObject class]; 
     kclass = objc_allocateClassPair(superClass, className, 0);
  }

b.使用class_addIvar添加一个成员变量

NSUInteger size;
  NSUInteger alignment;
  NSGetSizeAndAlignment("*", &size, &alignment);
  class_addIvar(kclass, "expression", size, alignment, "*");

c.使用class_addMethod添加成员方法

  class_addMethod(kclass, @selector(setExpressionFormula:), (IMP)setExpressionFormula, "v@:@");
   class_addMethod(kclass, @selector(getExpressionFormula), (IMP)getExpressionFormula, "@@:");

   static void setExpressionFormula(id self, SEL cmd, id value)
   {
      NSLog(@"call setExpressionFormula");
   }

   static void getExpressionFormula(id self, SEL cmd)
   {
       NSLog(@"call getExpressionFormula");
   } 

注:
1.type定义参考:
2."v@:@",解释v-返回值void类型,@-self指针id类型,:-SEL指针SEL类型,@-函数第一个参数为id类型
3."@@:",解释@-返回值id类型,@-self指针id类型,:-SEL指针SEL类型,

d.注册到运行时环境
objc_registerClassPair(kclass);
e.实例化类
id instance = [[kclass alloc] init];
f.给变量赋值
object_setInstanceVariable(instance, "expression", "1+1");
g.获取变量值
void * value = NULL;
object_getInstanceVariable(instance, "expression", &value);
h.调用函数
[instance performSelector:@selector(getExpressionFormula)];