iOS Sharing #02 | 2019-03-30

時間 2019-11-07

標籤 ios sharing 欄目 iOS 简体版

原文原文鏈接

答：類在編譯後會以 class_ro_t 的結構把類的信息存儲在 bits 裏，運行時的 realizeClass 以後，會把 ro 中的全部信息拷貝到 bits 的 data 內，即以 class_rw_t 的形式存在，分類裏的方法即在這個時候添加到類的方法表裏，並在方法表數組的最前面

四、class_addMethod()都須要什麼參數?

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);

複製代碼

給類添加一個新的方法和該方法的具體實現
BOOL: 返回值，YES -------方法添加成功 NO --------方法添加失敗
Class cls: 將要給添加方法的類，傳的類型［類名 class］
SEL name: 將要添加的方法名，傳的類型 @selector(方法名)
IMP imp：實現這個方法的函數，傳的類型
- 一、C語言寫法：（IMP）方法名
- 二、OC的寫法：class_getMethodImplementation(self,@selector(方法名：))
const char *types：表示咱們要添加的方法的返回值和參數
"v@:@"：
- 'v'是添加方法無返回值
- '@'表示是id(也就是要添加的類)
- '：'表示添加的方法類型
- '@'表示參數類型

const char *types含義表：
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)