iOS runtime 知识点整理

// ------ 动态创建类, 添加成员变量, 赋值并调用动态添加的方法 -------

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     // 动态创建People类, 继承自NSObject类
     // 额外空间     未知,通常设置为 0
     Class People = objc_allocateClassPair([NSObject class], "Person", );

     // 以NSString*为例
     // 变量size sizeof(NSString)
     // 对齐     指针类型的为log2(sizeof(NSString*))
     // 类型     @encode(NSString*)
     // 添加_name 成员变量
     BOOL flag1 = class_addIvar([People class], "_name", sizeof(NSString *), log2(sizeof(NSString *)), @encode(NSString *));
     if (flag1) {
         NSLog(@"添加成员变量_name成功!");
     }
     // 添加_age 成员变量
     BOOL flag2 = class_addIvar([People class], "_age", sizeof(int), sizeof(int), @encode(int));
     if (flag2) {
         NSLog(@"添加成员变量_age成功!");
     }

     // 注册方法名为say:的方法
     SEL s = sel_registerName("say:");

     // 添加say:方法的实现
     // "v@:@"
     // v表示返回值为void, i表示返回值为int
     // @表示参数id(self)
     // :表示SEL(_cmd)
     // @表示id
     class_addMethod([People class], s, (IMP)sayFunction1, "v@:@");

     // 注册该类
     objc_registerClassPair([People class]);

     // 创建类的实例
     id peopleInstance = [[People alloc] init];

     // KVC 动态改变 对象peopleInstance 中的实例变量
     [peopleInstance setValue:@"老师" forKey:@"name"];
     //    Ivar nameVar = class_getInstanceVariable([People class], "_name");
     //    object_setIvar(peopleInstance, nameVar, @"老师");

     // 从类中获取成员变量Ivar
     Ivar ageIvar = class_getInstanceVariable([People class], "_age");
     // 为成员变量赋值
     object_setIvar(peopleInstance, ageIvar, @);

     // 调用 peopleInstance 对象中的 s 方法选择器对应的方法
     //    objc_msgSend(peopleInstance, s, @"大家好!");
     ((void (*)(id, SEL, id))objc_msgSend)(peopleInstance, s, @"大家好!!!");

     // 当People类或者它的子类的实例还存在，则不能调用objc_disposeClassPair这个方法；因此这里要先销毁实例对象后才能销毁类；
     peopleInstance = nil;

     // 销毁类
     objc_disposeClassPair([People class]);
 }

 // 动态添加方法的实现
 void sayFunction1(id self, SEL _cmd, id some) {
     Ivar ageIvar = class_getInstanceVariable([self class], "_age");
     NSString *age = object_getIvar(self, ageIvar);
     NSLog(@"%@岁的%@说： %@, %@", age,[self valueForKey:@"name"],some, NSStringFromSelector(_cmd));
 }

// ------ 获取属性, 成员变量 以及 方法 -------

 @implementation People

 - (NSDictionary *)allProperties {
     unsigned int count = ;

     // 获取类的所有属性, 如果没有属性count就为0
     objc_property_t *properties = class_copyPropertyList([self class], &count);
     NSMutableDictionary *resultDict = [@{} mutableCopy];

     for (int i = ; i < count; i++) {
         // 获取属性的名称和值
         const char *propertyName = property_getName(properties[i]);
         NSString *name = [NSString stringWithUTF8String:propertyName];
         id propertyValue = [self valueForKey:name];

         if (propertyValue) {
             resultDict[name] = propertyValue;
         } else {
             resultDict[name] = @"字典的key对应的value不能为nil哦!";
         }
     }

     // 这里properties是一个数组指针, 我们需要使用free函数来释放内存
     free(properties);

     return resultDict;
 }

 - (NSDictionary *)allIvars {
     unsigned int count = ;
     NSMutableDictionary *resultDict = [@{} mutableCopy];

     // 获取类的所有成员变量ivar
     Ivar *ivars = class_copyIvarList([self class], &count);

     for (int i = ; i < count; i++) {
         const char *ivarName = ivar_getName(ivars[i]);
         NSString *name = [NSString stringWithUTF8String:ivarName];
         id ivarValue = [self valueForKey:name];

         if (ivarValue) {
             resultDict[name] = ivarValue;
         } else {
             resultDict[name] = @"字典的key对应的value不能为nil哦~";
         }
     }

     free(ivars);

     return resultDict;
 }

 - (NSDictionary *)allMethods {
     unsigned int count = ;
     NSMutableDictionary *resultDict = [@{} mutableCopy];

     Method *methods = class_copyMethodList([self class], &count);

     for (int i = ; i < count; i++) {
         SEL methodSEL = method_getName(methods[i]);
         const char *methodName = sel_getName(methodSEL);
         NSString *name = [NSString stringWithUTF8String:methodName];

         unsigned int arguments = method_getNumberOfArguments(methods[i]);

         resultDict[name] = @(arguments - );
     }

     free(methods);

     return resultDict;
 }

 @end

// ------- 给类添加 属性 及 回调block -------

 // 在People的分类中进行

 typedef void(^CodingCallBack)();

 @interface People (Associated)

 @property (strong, nonatomic) NSNumber *associatedBust; // 胸围
 @property (copy, nonatomic) CodingCallBack associatedCallBack; // 写代码

 @end

 @implementation People (Associated)

 - (NSNumber *)associatedBust {
     // 获取关联对象
     return objc_getAssociatedObject(self, @selector(associatedBust));
 }

 - (void)setAssociatedBust:(NSNumber *)associatedBust {
     // 设置关联对象
     objc_setAssociatedObject(self, @selector(associatedBust), associatedBust, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }

 - (CodingCallBack)associatedCallBack {
     return objc_getAssociatedObject(self, @selector(associatedCallBack));
 }

 - (void)setAssociatedCallBack:(CodingCallBack)associatedCallBack {
     objc_setAssociatedObject(self, @selector(associatedCallBack), associatedCallBack, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
 }

 @end

// ------- 序列化 及 反序列化 -------

 @interface People2 : NSObject <NSCoding>

 @property (nonatomic, copy) NSString *name; // 姓名
 @property (nonatomic, strong) NSNumber *age; // 年龄
 @property (nonatomic, copy) NSString *occupation; // 职业
 @property (nonatomic, copy) NSString *nationality; // 国籍

 @end

 @implementation People2

 // 反序列化数据
 - (instancetype)initWithCoder:(NSCoder *)coder
 {
     self = [super init];
     if (self) {
         unsigned int count = ;
         Ivar *ivars = class_copyIvarList([self class], &count);

         for (int i = ; i < count; i++) {
             const char *ivarName = ivar_getName(ivars[i]);
             NSString *name = [NSString stringWithUTF8String:ivarName];
             id value = [coder decodeObjectForKey:name];

             [self setValue:value forKey:name];
         }

         free(ivars);
     }
     return self;
 }

 // 序列化数据
 - (void)encodeWithCoder:(NSCoder *)aCoder {
     unsigned int count = ;
     Ivar *ivars = class_copyIvarList([self class], &count);

     for (int i = ; i < count; i++) {
         const char *ivarName = ivar_getName(ivars[i]);
         NSString *name = [NSString stringWithUTF8String:ivarName];
         id ivarValue = [self valueForKey:name];

         [aCoder encodeObject:ivarValue forKey:name];
     }

     free(ivars);
 }

 @end

// ------- Json 及 model 互转 -------

 @interface People2 : NSObject

 @property (nonatomic, copy) NSString *name; // 姓名
 @property (nonatomic, strong) NSNumber *age; // 年龄
 @property (nonatomic, copy) NSString *occupation; // 职业
 @property (nonatomic, copy) NSString *nationality; // 国籍

 // 生成model
 - (instancetype)initWithDictionary:(NSDictionary *)dictionary;

 // 转换成字典
 - (NSDictionary *)covertToDictionary;

 @end

 @implementation People2

 - (instancetype)initWithDictionary:(NSDictionary *)dictionary {
     self = [super init];
     if (self) {
         for (NSString *key in dictionary.allKeys) {
             id value = dictionary[key];

             SEL setter = [self propertySetterByKey:key];
             if (setter) {
                 //                objc_msgSend(self, setter, value);
                 ((void(*)(id, SEL, id))objc_msgSend)(self, setter, value);
             }
         }
     }
     return self;
 }

 - (NSDictionary *)covertToDictionary {
     unsigned int count = ;
     objc_property_t *properties = class_copyPropertyList([self class], &count);

     if (count != ) {
         NSMutableDictionary *resultDict = [@{} mutableCopy];

         for (int i = ; i < count; i++) {
             const char *propertyName = property_getName(properties[i]);
             NSString *key = [NSString stringWithUTF8String:propertyName];

             SEL getter = [self propertyGetterByKey:key];
             if (getter) {
                 id value = ((id (*)(id, SEL))objc_msgSend)(self, getter);
                 if (value) {
                     resultDict[key] = value;
                 } else {
                     resultDict[key] = @"字典的key对应的value不能为nil哦!";
                 }
             }
         }

         free(properties);
         return resultDict;
     }

     free(properties);
     return nil;
 }

 // --------- private method --------------------------------------
 - (SEL)propertySetterByKey:(NSString *)key {
     // set方法, 首字母大写
     NSString *propertySetterName = [NSString stringWithFormat:@"set%@:", key.capitalizedString];

     SEL setter = NSSelectorFromString(propertySetterName);
     if ([self respondsToSelector:setter]) {
         return setter;
     }
     return nil;
 }

 - (SEL)propertyGetterByKey:(NSString *)key {
     SEL getter = NSSelectorFromString(key);
     if ([self respondsToSelector:getter]) {
         return getter;
     }
     return nil;
 }

 @end

// ------- 动态转换方法实现 --------

 // 添加了方法声明, 但是没有实现该方法
 @interface People : NSObject

 - (void)sing;

 @end

 @implementation People

 + (BOOL)resolveInstanceMethod:(SEL)sel {
     // 我们没有给People类声明sing方法, 这里我们动态添加方法
     if ([NSStringFromSelector(sel) isEqualToString:@"sing"]) {
         class_addMethod([self class], sel, (IMP)otherSing, "v@:");
         return YES;
     }
     return [super resolveClassMethod:sel];
 }

 void otherSing(id self, SEL cmd) {
     NSLog(@"%@ 唱歌啦~~",((People *)self).name);
 }

 @end

// ------- 修改方法调用对象 --------

 // Bird 类中并没有名字为 sing 的方法, 这时可以在Bird类中 将对象修改成People
 @interface Bird : NSObject

 @property (copy, nonatomic) NSString *name;

 @end

 @implementation Bird

 // 第一步：我们不动态添加方法，返回NO，进入第二步；
 + (BOOL)resolveInstanceMethod:(SEL)sel {
     return NO;
 }

 // 第二部：我们不指定备选对象响应aSelector，进入第三步；
 - (id)forwardingTargetForSelector:(SEL)aSelector {
     return nil;
 }

 // 第三步：返回方法选择器，然后进入第四部；
 - (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
     if ([NSStringFromSelector(aSelector) isEqualToString:@"sing"]) {
         return [NSMethodSignature signatureWithObjCTypes:"v@:"];
     }
     return [super methodSignatureForSelector:aSelector];
 }

 // 第四部：这步我们修改调用对象
 - (void)forwardInvocation:(NSInvocation *)anInvocation {
 // 我们改变调用对象为People
     People *p = [[People alloc] init];
     p.name = @"t1";

     [p sing];
 }

 @end

// ------- 修改调用的方法 -------

 @interface Bird : NSObject

 @property (copy, nonatomic) NSString *name;

 @end

 @implementation Bird

 // 第一步：我们不动态添加方法，返回NO，进入第二步；
 + (BOOL)resolveInstanceMethod:(SEL)sel {
     return NO;
 }

 // 第二部：我们不指定备选对象响应aSelector，进入第三步；
 - (id)forwardingTargetForSelector:(SEL)aSelector {
     return nil;
 }

 // 第三步：返回方法选择器，然后进入第四部；
 - (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
     if ([NSStringFromSelector(aSelector) isEqualToString:@"sing"]) {
         return [NSMethodSignature signatureWithObjCTypes:"v@:"];
     }
     return [super methodSignatureForSelector:aSelector];
 }

 // 第四部：这步我们修改调用方法
 - (void)forwardInvocation:(NSInvocation *)anInvocation {
     [anInvocation setSelector:@selector(dance)];
     // 还要指定是哪个对象的方法
     [anInvocation invokeWithTarget:self];
 }

 // 若forwardInvocation没有实现，则会调用此方法
 - (void)doesNotRecognizeSelector:(SEL)aSelector {
     NSLog(@"消息无法处理: %@", NSStringFromSelector(aSelector));
 }

 - (void)dance {
     NSLog(@"跳舞!! come on!~");
 }

 @end