BOOL class_addMethod(Class _Nullable cls, SEL _Nonnull name, IMP _Nonnull imp, const char * _Nullable types)

在runtime.h中定义, 其作用是给一个类添加新的方法及该方法的具体实现.

其 返回值为 BOOL 类型, yes表示添加方法成功, no表示添加方法失败.

参数介绍

/** * Adds a new method to a class with a given name and implementation.* * @param cls 将要添加方法的类, 可以传 [类名 class] * @param name 将要添加的方法名, 传的类型为 @selector(方法名).* @param imp 实现这个方法的函数, 传的类型 (1) C语言写法: (IMP) 方法名; (2) OC写法: class_getMethodImplementation(self, @selector(方法名))* @param types 添加方法的返回值和参数数组 */

举例:

(1) C语言举例

void exchange_function(id self, SEL _cmd, NSString *str){NSLog(@"exchange_function");
}@implementation myClass : NSObject- (void)exchangeMethodWithSel:(SEL)sel{class_addMethod([self class], sel, (IMP)exchange_function, "v@:@");
}@end

(2) OC方法举例

@implementation myClass : NSObject- (void)exchange_functionTwo:(NSString *)str{NSLog(@"exchange_functionTwo");
}- (void)exchangeMethodWithSel:(SEL)sel{// "v@:@"：v表示是添加方法无返回值,     @表示是id(也就是要添加的类); ：表示添加的方法类型   @表示：参数类型class_addMethod([self class], sel, class_getMethodImplementation([self class], @selector(exchange_functionTwo:)), "v@:@");
}@end

注释: 

const char *type 含义

Code	Meaning
c	A char
i	An int
s	A short
l	A long
q	A long long
C	An unsigned char
I(大写i)	An unsigned int
S	An unsigned short
L	An unsigned Long
Q	An unsigned long long
f	A float
d	A double
B	A C++ bool or C99 _Bool
v	A void
*	A character string (char *)
@	An object (whether statically typed or typed id)
#	A class object (Class)
:	A method selector (SEL)
[array type]	An array
{name=type...}	A structure
(name=type...)	A union
bnum	A bit field of num bits
^type	A pointer to type
?	An unknown type (among other things, this code is used for function pointers)