struct objc_method {
SEL _Nonnull method_name OBJC2_UNAVAILABLE;
char * _Nullable method_types OBJC2_UNAVAILABLE;
IMP _Nonnull method_imp OBJC2_UNAVAILABLE;
}
@encode:
将数据类型编码成char＊（字符串）形式
https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/ObjCRuntimeGuide.pdf
To assist the runtime system, the compiler encodes the return and argument types for each method in a character string and associates the string with the method selector. The coding scheme it uses is also useful in other contexts and so is made publicly available with the @encode() compiler directive. When given a type specification, @encode() returns a string encoding that type. The type can be a basic type such as an int, a pointer, a tagged structure or union, or a class name—any type, in fact, that can be used as an argument to the C sizeof() operator.
method_getTypeEncoding
使用@encode将消息编码成字符串形式。
编码的格式按照
id objc_msgSend(id self, SEL op, ...)
参量的顺序进行布局。
-(void)log:(SEL)sel
{
Method xxx = class_getInstanceMethod(self.class, sel);
char *ret = method_getTypeEncoding(xxx);
NSLog(@"sel:%s, %s", sel, ret);
}
举例：
-(void)hello
v16@0:8
-(id)hello:(id)x
@24@0:8@16
-(void)hello:(id)x :(id)e
v32@0:8@16@24
解读：
按照文档上的说明，和objc_msgSend的参量顺序
A void v
A method selector (SEL) ：
An object (whether statically typed or typed id) @
进行拆解解读
v16（返回类型为空） @0（receiver id类型） :8（SEL标示）
v32（返回类型为空） @0（receiver id类型） :8（SEL标示）@16（参量 id类型）@24（参量 id类型）