動態(tài)創(chuàng)建類Class,動態(tài)添加Class成員變量與成員函數(shù),動態(tài)變量賦值與取值，動態(tài)函數(shù)調(diào)用等方法

a.使用objc_allocateClassPair創(chuàng)建一個類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添加一個成員變量

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

c.使用class_addMethod添加成員方法

  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定義參考:
2."v@:@",解釋v-返回值void類型,@-self指針id類型,:-SEL指針SEL類型,@-函數(shù)第一個參數(shù)為id類型
3."@@:",解釋@-返回值id類型,@-self指針id類型,:-SEL指針SEL類型,

d.注冊到運行時環(huán)境
objc_registerClassPair(kclass);
e.實例化類
id instance = [[kclass alloc] init];
f.給變量賦值
object_setInstanceVariable(instance, "expression", "1+1");
g.獲取變量值
void * value = NULL;
object_getInstanceVariable(instance, "expression", &value);
h.調(diào)用函數(shù)
[instance performSelector:@selector(getExpressionFormula)];