iOS中的Runtime

Student *student = [[Student alloc] init];
[student personTest];

// 假设这里有一个other方法
- (void)other
{
    NSLog(@"%s", __func__);
}
// 动态方法解析
+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    // 判断一下是我们想要捕捉的test方法
    if (sel == @selector(test)) {
        // 获取other方法
        // Method可以理解为等价于struct method_t *
        Method method = class_getInstanceMethod(self, @selector(other));

        // 动态添加test方法的实现
        class_addMethod(self, sel,
                        method_getImplementation(method),
                        method_getTypeEncoding(method));

        // 返回YES代表有动态添加方法
        return YES;
    }
    return [super resolveInstanceMethod:sel];
}

// 如果是类方法，就会进入到这里，处理流程一样
+ (BOOL)resolveClassMethod:(SEL)sel;

// 消息转发,可以将selector转发到别的类当中实现
- (id)forwardingTargetForSelector:(SEL)aSelector
{
    if (aSelector == @selector(test)) {
        return [[Person alloc] init];
    }
    
    return [super forwardingTargetForSelector:aSelector];
}

// 方法签名：告诉方法的返回值类型、参数类型
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector
{
    if (aSelector == @selector(test:)) {
    // return [NSMethodSignature signatureWithObjCTypes:"v20@0:8i16"];
        return [NSMethodSignature signatureWithObjCTypes:"i@:i"];
    // return [[[MyCat alloc] init] methodSignatureForSelector:aSelector];
    }
    return [super methodSignatureForSelector:aSelector];
}

// NSInvocation封装了一个方法调用，包括：方法调用者、方法名、方法参数
// anInvocation.target：方法调用者
// anInvocation.selector：方法名
// [anInvocation getArgument:&age atIndex:2]; 参数
- (void)forwardInvocation:(NSInvocation *)anInvocation
{
    // 参数顺序：receiver、selector、other arguments
    //    int age;
    //    [anInvocation getArgument:&age atIndex:2];
    //    NSLog(@"%d", age + 10);
    
    // 这种调用是可以的
    // anInvocation.target == [[MyCat alloc] init]
    // [anInvocation invoke];
    
    // 这种调用也是可以的
    [anInvocation invokeWithTarget:[[MyCat alloc] init]];
    
    //    int ret;
    //    [anInvocation getReturnValue:&ret];
    //    NSLog(@"%d", ret);
}

[self class]; // 当前类对象
[self superclass]; // 当前类的父类的类对象
[super class]; // 当前类对象
[super superclass]; // 当前类的父类的类对象

// objc_super2 定义
// receiver是消息接收者
// current_class是receiver的Class对象
struct objc_super {
    id receiver;
    Class current_class;
}

- (BOOL)isMemberOfClass:(Class)cls {
    return [self class] == cls;
}

- (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = [self class]; tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES
    }
    return NO;
}

// 这句代码的方法调用者不管是哪个类（只要是NSObject体系下的），都返回YES
NSLog(@"%d", [NSObject isKindOfClass:[NSObject class]]); // 1
NSLog(@"%d", [NSObject isMemberOfClass:[NSObject class]]); // 0
NSLog(@"%d", [MyPerson isKindOfClass:[MyPerson class]]); // 0
NSLog(@"%d", [MyPerson isMemberOfClass:[MyPerson class]]); // 0

+ (BOOL)isMemberOfClass:(Class)cls {
    return object_getClass((id)self) == cls;
}

+ (BOOL)isKindOfClass:(Class)cls {
    for (Class tcls = object_getClass((id)self); tcls; tcls = tcls->superclass) {
        if (tcls == cls) return YES;
    }
    return NO;
}

// 成员变量的数量
unsigned int count;
Ivar *ivars = class_copyIvarList([MyPerson class], &count);
for (int i = 0; i < count; i++) {
    // 取出i位置的成员变量
    Ivar ivar = ivars[i];
    NSLog(@"%s %s", ivar_getName(ivar), ivar_getTypeEncoding(ivar));
}
free(ivars);

self.textField.placeholder = @"请输入用户名";
[self.textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];

+ (instancetype)objectWithJson:(NSDictionary *)json
{
    id obj = [[self alloc] init];
    
    unsigned int count;
    Ivar *ivars = class_copyIvarList(self, &count);
    for (int i = 0; i < count; i++) {
        // 取出i位置的成员变量
        Ivar ivar = ivars[i];
        NSMutableString *name = [NSMutableString stringWithUTF8String:ivar_getName(ivar)];
        [name deleteCharactersInRange:NSMakeRange(0, 1)];
        
        // 设值
        id value = json[name];
        if ([name isEqualToString:@"ID"]) {
            value = json[@"id"];
        }
        [obj setValue:value forKey:name];
    }
    free(ivars);
    
    return obj;
}

Class objc_allocateClassPair(Class superclass, const char *name, size_t extraBytes)

void objc_registerClassPair(Class cls) 

void objc_disposeClassPair(Class cls)

Class object_getClass(id obj)

Class object_setClass(id obj, Class cls)

BOOL object_isClass(id obj)

BOOL class_isMetaClass(Class cls)

Class class_getSuperclass(Class cls)

Ivar class_getInstanceVariable(Class cls, const char *name)

Ivar *class_copyIvarList(Class cls, unsigned int *outCount)

void object_setIvar(id obj, Ivar ivar, id value)
id object_getIvar(id obj, Ivar ivar)

BOOL class_addIvar(Class cls, const char * name, size_t size, uint8_t alignment, const char * types)

const char *ivar_getName(Ivar v)
const char *ivar_getTypeEncoding(Ivar v)

objc_property_t class_getProperty(Class cls, const char *name)

objc_property_t *class_copyPropertyList(Class cls, unsigned int *outCount)

BOOL class_addProperty(Class cls, const char *name, const objc_property_attribute_t *attributes,
              unsigned int attributeCount)

void class_replaceProperty(Class cls, const char *name, const objc_property_attribute_t *attributes,
                  unsigned int attributeCount)

const char *property_getName(objc_property_t property)
const char *property_getAttributes(objc_property_t property)

Method class_getInstanceMethod(Class cls, SEL name)
Method class_getClassMethod(Class cls, SEL name)

IMP class_getMethodImplementation(Class cls, SEL name) 
IMP method_setImplementation(Method m, IMP imp)
void method_exchangeImplementations(Method m1, Method m2) 

Method *class_copyMethodList(Class cls, unsigned int *outCount)

BOOL class_addMethod(Class cls, SEL name, IMP imp, const char *types)

IMP class_replaceMethod(Class cls, SEL name, IMP imp, const char *types)

SEL method_getName(Method m)
IMP method_getImplementation(Method m)
const char *method_getTypeEncoding(Method m)
unsigned int method_getNumberOfArguments(Method m)
char *method_copyReturnType(Method m)
char *method_copyArgumentType(Method m, unsigned int index)

const char *sel_getName(SEL sel)
SEL sel_registerName(const char *str)

IMP imp_implementationWithBlock(id block)
id imp_getBlock(IMP anImp)
BOOL imp_removeBlock(IMP anImp)