简单的实用iOS运行时

objective - c语言尽可能许多决定推迟时间运行时编译时间和链接。只要有可能,它动态地事情。这意味着语言需要的不仅仅是一个编译器,但也一个运行时系统来执行编译后的代码。运行时系统作为一种操作系统的objective - c语言;这就是使语言文字工作。本文着眼于NSObject类和objective - c程序如何与运行时系统交互。特别是,它检查在运行时动态加载新类的范例,并将消息转发给其他对象。它还提供了关于如何找到信息对象的信息,而您的程序正在运行。 —来自苹果官方文档

应用场景

1.遍历属性

unsigned int count = 0;
Ivar *ivar = class_copyIvarList([self.person class], &count);

for (int i = 0; i<count; i++) {
Ivar var = ivar[i];
const char *varName = ivar_getName(var);
NSString *proname = [NSString stringWithUTF8String:varName];

if ([proname isEqualToString:@"_name"]) {   //这里别忘了给属性加下划线
object_setIvar(self.person, var, @"daming");
break;
}
}

2.动态创建方法

- (void)sayFrom
{

class_addMethod([self.person class], @selector(guess), (IMP)guessAnswer, "v@:");
if ([self.person respondsToSelector:@selector(guess)]) {
//Method method = class_getInstanceMethod([self.xiaoMing class], @selector(guess));
[self.person performSelector:@selector(guess)];

} else{
NSLog(@"Sorry,I don't know");
}
self.textview.text = @"beijing";
}

void guessAnswer(id self,SEL _cmd){

NSLog(@"i am from beijing");

}

3.动态交换两个方法

Method m1 = class_getInstanceMethod([self.person class], @selector(sayName));
Method m2 = class_getInstanceMethod([self.person class], @selector(saySex));

method_exchangeImplementations(m1, m2);

4.在一个类运行的时候,动态的替换掉该类的方法

Method m1 = class_getInstanceMethod([Person class], @selector(sayName));
Method m2 = class_getInstanceMethod([Tool class], @selector(changeMethod));

method_exchangeImplementations(m1, m2);

5.实现归档和反归档

// 字典转模型

+ (instancetype)objectWithDict:(NSDictionary *)dict
{
// 创建对应模型对象
id objc = [[self alloc] init];
unsigned int count = 0;
// 1.获取成员属性数组
Ivar *ivarList = class_copyIvarList(self, &count);

// 2.遍历所有的成员属性名,一个一个去字典中取出对应的value给模型属性赋值
for (int i = 0; i < count; i++) {

// 2.1 获取成员属性
Ivar ivar = ivarList[i];

// 2.2 获取成员属性名 C -> OC 字符串
NSString *ivarName = [NSString stringWithUTF8String:ivar_getName(ivar)];

// 2.3 _成员属性名 => 字典key
NSString *key = [ivarName substringFromIndex:1];

// 2.4 去字典中取出对应value给模型属性赋值
id value = dict[key];

// 获取成员属性类型
NSString *ivarType = [NSString stringWithUTF8String:ivar_getTypeEncoding(ivar)];

// 二级转换,字典中还有字典,也需要把对应字典转换成模型
//
// 判断下value,是不是字典
if ([value isKindOfClass:[NSDictionary class]] && ![ivarType containsString:@"NS"]) { //  是字典对象,并且属性名对应类型是自定义类型
// user User

// 处理类型字符串 @\"User\" -> User
ivarType = [ivarType stringByReplacingOccurrencesOfString:@"@" withString:@""];
ivarType = [ivarType stringByReplacingOccurrencesOfString:@"\"" withString:@""];
// 自定义对象,并且值是字典
// value:user字典 -> User模型
// 获取模型(user)类对象
Class modalClass = NSClassFromString(ivarType);

// 字典转模型
if (modalClass) {
// 字典转模型 user
value = [modalClass objectWithDict:value];
}

// 字典,user
//            NSLog(@"%@",key);
}

// 三级转换：NSArray中也是字典，把数组中的字典转换成模型.
// 判断值是否是数组
if ([value isKindOfClass:[NSArray class]]) {
// 判断对应类有没有实现字典数组转模型数组的协议
if ([self respondsToSelector:@selector(arrayContainModelClass)]) {

// 转换成id类型，就能调用任何对象的方法
id idSelf = self;

// 获取数组中字典对应的模型
NSString *type =  [idSelf arrayContainModelClass][key];

// 生成模型
Class classModel = NSClassFromString(type);
NSMutableArray *arrM = [NSMutableArray array];
// 遍历字典数组，生成模型数组
for (NSDictionary *dict in value) {
// 字典转模型
id model =  [classModel objectWithDict:dict];
[arrM addObject:model];
}

// 把模型数组赋值给value
value = arrM;

}
}

// 2.5 KVC字典转模型
if (value) {

[objc setValue:value forKey:key];
}
}

// 返回对象
return objc;

}

归档

- (void)encodeWithCoder:(NSCoder *)encoder

{
unsigned int count = 0;

Ivar *ivars = class_copyIvarList([Movie class], &count);

for (int i = 0; i<count; i++) {
// 取出i位置对应的成员变量
Ivar ivar = ivars[i];
// 查看成员变量

const char *name = ivar_getName(ivar);
// 归档
NSString *key = [NSString stringWithUTF8String:name];
id value = [self valueForKey:key];
[encoder encodeObject:value forKey:key];

}

free(ivars);

}

反归档

- (id)initWithCoder:(NSCoder *)decoder
{
if (self = [super init]) {
unsigned int count = 0;
Ivar *ivars = class_copyIvarList([Movie class], &count);
for (int i = 0; i<count; i++) {
// 取出i位置对应的成员变量
Ivar ivar = ivars[i];
// 查看成员变量
const char *name = ivar_getName(ivar);
// 归档
NSString *key = [NSString stringWithUTF8String:name];
id value = [decoder decodeObjectForKey:key];
// 设置到成员变量身上
[self setValue:value forKey:key];

}
free(ivars);

}

return self;
}

总结:

详情请转至 https://github.com/WM520/runtime-API