运行时c函数
// 修改isa,本质就是改变当前对象的类名
object_setClass(self, [XMGKVONotifying_Person class]);
// self动态添加关联
// id object:给哪个对象添加关联属性
// key:属性名
// value:关联值
//objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy)
objc_setAssociatedObject(self, @"observer", observer, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
// self获取关联
//objc_getAssociatedObject(id object, const void *key)
id observer = objc_getAssociatedObject(self, @"observer");
默认情况下，如果是以[object message]的方式调用方法，如果object无法响应message消息时，编译器会报错。但如果是以perform…的形式来调用，则需要等到运行时才能确定object是否能接收message消息。如果不能，则程序崩溃。
通常，当我们不能确定一个对象是否能接收某个消息时，会先调用respondsToSelector:来判断一下。如下代码所示：
if ([self respondsToSelector:@selector(method)]) { [self performSelector:@selector(method)]; }
摘录其它博客：
@implementation HYBMethodLearn - (int)testInstanceMethod:(NSString *)name andValue:(NSNumber *)value { NSLog(@"%@", name); return value.intValue; } - (void)getMethods { unsigned int outCount = 0; Method *methodList = class_copyMethodList(self.class, &outCount); for (unsigned int i = 0; i < outCount; ++i) { Method method = methodList[i]; SEL methodName = method_getName(method); NSLog(@"方法名：%@", NSStringFromSelector(methodName)); // 获取方法的参数类型 unsigned int argumentsCount = method_getNumberOfArguments(method); char argName[512] = {}; for (unsigned int j = 0; j < argumentsCount; ++j) { method_getArgumentType(method, j, argName, 512); NSLog(@"第%u个参数类型为：%s", j, argName); memset(argName, '\0', strlen(argName)); } char returnType[512] = {}; method_getReturnType(method, returnType, 512); NSLog(@"返回值类型：%s", returnType); // type encoding NSLog(@"TypeEncoding: %s", method_getTypeEncoding(method)); } free(methodList); } + (void)test { HYBMethodLearn *m = [[HYBMethodLearn alloc] init]; // [m getMethods]; ((void (*)(id, SEL))objc_msgSend)((id)m, @selector(getMethods)); // 这就是为什么有四个参数的原因 int returnValue = ((int (*)(id, SEL, NSString *, NSNumber *)) objc_msgSend)((id)m, @selector(testInstanceMethod:andValue:), @"标哥的技术博客", @100); NSLog(@"return value is %d", returnValue); // 获取方法 Method method = class_getInstanceMethod([self class], @selector(testInstanceMethod:andValue:)); // 调用函数 returnValue = ((int (*)(id, Method, NSString *, NSNumber *))method_invoke)((id)m, method, @"测试使用method_invoke", @11); NSLog(@"call return vlaue is %d", returnValue); }
给NSMutableArray添加分类
#import "NSMutableArray+Swizzling.h" #import <objc/runtime.h> #import <objc/message.h> @implementation NSMutableArray (Swizzling) +(void)load { static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ //NSMutableArray －－－－>__NSArrayM Method method=class_getInstanceMethod(objc_getClass("__NSArrayM"), @selector(objectAtIndex:)); Method method2=class_getInstanceMethod(objc_getClass("__NSArrayM"), @selector(fdc_objectAtIndex:)); method_exchangeImplementations(method, method2); }); } -(id)fdc_objectAtIndex:(NSInteger)index { // NSLog(@"%s",__func__); 千万别加上这句 不然有bug if (self.count == 0) { NSLog(@"%s can't get any object from an empty array", __FUNCTION__); return nil; } if (index > self.count) { NSLog(@"%s index out of bounds in array", __FUNCTION__); return nil; } return [self fdc_objectAtIndex:index]; } @end
Student *obj=[[Student alloc]init]; NSLog(@"instance :%p", obj); NSLog(@"---------------------------------------------"); NSLog(@"class :%p", object_getClass(obj)); NSLog(@"meta class :%p", object_getClass(object_getClass(obj))); NSLog(@"root meta :%p", object_getClass(object_getClass(object_getClass(obj)))); NSLog(@"root meta's meta :%p", object_getClass(object_getClass(object_getClass(object_getClass(obj))))); NSLog(@"---------------------------------------------"); NSLog(@"class :%p", [obj class]); NSLog(@"meta class :%p", [[obj class] class]); NSLog(@"root meta :%p", [[[obj class] class] class]); NSLog(@"root meta's meta :%p", [[[[obj class] class] class] class]);
2016-07-14 10:24:05.074 测试[1145:46819] instance :0x7fed2276d9c0 2016-07-14 10:24:05.075 测试[1145:46819] --------------------------------------------- 2016-07-14 10:24:05.075 测试[1145:46819] class :0x101417060 2016-07-14 10:24:05.075 测试[1145:46819] meta class :0x101417038 2016-07-14 10:24:05.076 测试[1145:46819] root meta :0x101c75198 2016-07-14 10:24:05.076 测试[1145:46819] root meta's meta :0x101c75198 2016-07-14 10:24:05.076 测试[1145:46819] --------------------------------------------- 2016-07-14 10:24:05.076 测试[1145:46819] class :0x101417060 2016-07-14 10:24:05.076 测试[1145:46819] meta class :0x101417060 2016-07-14 10:24:05.077 测试[1145:46819] root meta :0x101417060 2016-07-14 10:24:05.077 测试[1145:46819] root meta's meta :0x101417060
类簇：
类簇的概念：一个父类有好多子类，父类在返回自身对象的时候，向外界隐藏各种细节，根据不同的需要返回的其实是不同的子类对象，这其实就是抽象类工厂的实现思路，iOS最典型的就是NSNumber。
NSNumber，NSArray，NSDictionary、NSString、NSTimer…这说明大多数的OC类都是类簇实现的；
NSNumber *intNum = [NSNumber numberWithInt:1]; NSNumber *boolNum = [NSNumber numberWithBool:YES]; NSLog(@"intNum :%@", [intNum class]); NSLog(@"boolNum:%@", [boolNum class]); NSLog(@"Superclass:%@", class_getSuperclass([boolNum class])); NSLog(@"Superclass:%@", class_getSuperclass([intNum class]));
2016-07-14 10:30:21.166 测试[1179:51674] intNum :__NSCFNumber 2016-07-14 10:30:21.167 测试[1179:51674] boolNum:__NSCFBoolean 2016-07-14 10:30:21.167 测试[1179:51674] Superclass:NSNumber 2016-07-14 10:30:21.167 测试[1179:51674] Superclass:NSNumber
