iOS Sharing #02 | 2019-03-30

时间 2019-11-07

标签 ios sharing 栏目 iOS 繁體版

原文原文链接

答：类在编译后会以 class_ro_t 的结构把类的信息存储在 bits 里，运行时的 realizeClass 以后，会把 ro 中的全部信息拷贝到 bits 的 data 内，即以 class_rw_t 的形式存在，分类里的方法即在这个时候添加到类的方法表里，并在方法表数组的最前面

四、class_addMethod()都须要什么参数?

答：

/** * Adds a new method to a class with a given name and implementation. * * @param cls The class to which to add a method. * @param name A selector that specifies the name of the method being added. * @param imp A function which is the implementation of the new method. The function must take at least two arguments—self and _cmd. * @param types An array of characters that describe the types of the arguments to the method. * * @return YES if the method was added successfully, otherwise NO * (for example, the class already contains a method implementation with that name). * * @note class_addMethod will add an override of a superclass's implementation, * but will not replace an existing implementation in this class. * To change an existing implementation, use method_setImplementation. */
OBJC_EXPORT BOOL class_addMethod(Class cls, SEL name, IMP imp,
const char *types)
__OSX_AVAILABLE_STARTING(__MAC_10_5, __IPHONE_2_0);

复制代码

给类添加一个新的方法和该方法的具体实现
BOOL: 返回值，YES -------方法添加成功 NO --------方法添加失败
Class cls: 将要给添加方法的类，传的类型［类名 class］
SEL name: 将要添加的方法名，传的类型 @selector(方法名)
IMP imp：实现这个方法的函数，传的类型
- 一、C语言写法：（IMP）方法名
- 二、OC的写法：class_getMethodImplementation(self,@selector(方法名：))
const char *types：表示咱们要添加的方法的返回值和参数
"v@:@"：
- 'v'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

const char *types含义表：
github

Code	Meaning
c	A char
i	An int
s	A short
l	A long l is treated as a 32-bit quantity on 64-bit programs.
q	A long long
C	An unsigned char
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 a 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)