【Objective-C Runtime动态加载】---动态创建类Class

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, "*");

注:

1.type定义参考:https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html

2."*"星号代表字符(),iOS字符为4位，并采用4位对齐kclass

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:https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtTypeEncodings.html

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)];