NSObject头文件解析 / 消息机制 / Runtime解读 (二)
NSObject头文件解析 / 消息机制 / Runtime解读 (二)
周希
发布于 2019-10-15 01:29:03
发布于 2019-10-15 01:29:03
本章接着NSObject头文件解析 / 消息机制 / Runtime解读(一)写
给类添加属性:
BOOL class_addProperty(Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount)其中有一个参数我们再在上一篇中提到过
typedef struct {
const char *name; /**< The name of the attribute */
const char *value; /**< The value of the attribute (usually empty) */
} objc_property_attribute_t;
我们看下常见的赋值
常用attribute | name | value |
|---|---|---|
nonatomic | "N" | "" |
strong/retain | "&" | "" |
weak | "W" | "" |
属性的类型type | "T" | "@TypeName", eg"@\"NSString\"" |
属性对应的实例变量Ivar | "V" | "Ivar_name", eg "_name" |
readonly | "R" | "" |
getter | "G" | "GetterName", eg"isRight" |
setter | "S" | "SetterName", eg"setName" |
assign/atomic | 默认即为assign和retain |
例子:
- (void)viewDidLoad {
[super viewDidLoad];
//创建一个对象
ClassA *aClass = [ClassA new];
//创建一个attributes
objc_property_attribute_t nonatmoic = {"N", ""};
objc_property_attribute_t strong = {"&", ""};
objc_property_attribute_t type = {"T", "@\"NSString\""};
objc_property_attribute_t ivar = {"V", "_name"};
objc_property_attribute_t attributes[] = {nonatmoic, strong, type, ivar, getter, setter};
//给对象类添加属性
BOOL result = class_addProperty([aClass class], "name", attributes, 4);
if (result) {
NSLog(@"添加成功");
} else {
NSLog(@"添加失败");
}
//读取添加属性
objc_property_t property = class_getProperty([aClass class], "name");
//获取添加的属性的名称
NSString *propertyName = [NSString stringWithUTF8String:property_getName(property)];
//打印获取到的属性名
NSLog(@"获取到的属性名为: %@", propertyName);
}运行结果:
2017-02-03 15:52:01.949 RunTimeDemo[786:37263] 添加成功
2017-02-03 15:52:01.949 RunTimeDemo[786:37263] 获取到的属性名为: name替换属性:
void class_replaceProperty(Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount)例子:
//创建一个对象
ClassA *aClass = [ClassA new];
//创建一个attributes
objc_property_attribute_t nonatmoic = {"N", ""};
objc_property_attribute_t strong = {"&", ""};
objc_property_attribute_t type = {"T", "@\"NSString\""};
objc_property_attribute_t ivar = {"V", "_name"};
objc_property_attribute_t attributes[] = {nonatmoic, strong, type, ivar};
//替换属性
class_replaceProperty([aClass class], "name", attributes, 4);运行时创建新类:
Class objc_allocateClassPair(Class superclass, const char *name,
size_t extraBytes)注册创建的新类:
void objc_registerClassPair(Class cls) 例子:
void printA(){
NSLog(@"Print A");
}
- (void)viewDidLoad {
[super viewDidLoad];
//创新新类
Class NewClass = objc_allocateClassPair([NSObject class], "NewObject", 0);
//注册类
objc_registerClassPair(NewClass);
//给类添加方法
class_addMethod([NewClass class], @selector(printA), (IMP)printA, "v@:");
//创建实例
id ob = [NewClass new];
//实例执行方法
[ob printA];
}运行结果:
2017-02-03 18:11:34.091 RunTimeDemo[1114:96700] Print A先Mark在这里, 后面会继续更新
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原始发表：2017-02-21 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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