Objective-C runtime 常用api及示例

列举一些常用的运行时api. 本文Demo

Demo类代码

Cat.h

@protocol Cute
@optional
- (void)isCute;
@end

@protocol Movable
@optional
- (void)run;
@end

@interface Cat : NSObject<Movable>
@property (nonatomic, copy) NSString *name;
- (void)mew;
@end

Cat.m

@implementation Cat {
    NSColor *_color;
}

+ (void)mews {
    NSLog(@"+++++喵+++++");
}

- (instancetype)init {
    self = [super init];
    if (self) {
        _color = [NSColor blackColor];
    }
    return self;
}

- (void)mew {
    NSLog(@"-----喵-----");
}

- (void)run {
    NSLog(@"~~run~~");
}

- (NSArray *)method0:(NSArray *)agu0
                agu1:(CGFloat)agu1
                agu2:(NSObject *)agu2
                agu3:(NSString *)agu3
                agu4:(CGRect)agu4 {
    
    NSLog(@"test method");
    return @[];
}

- (void)method0 {
    NSLog(@">>>>>>>>0:%s", __func__);
}
- (void)method1 {
    NSLog(@">>>>>>>>1:%s", __func__);
}
- (void)method2 {
    NSLog(@">>>>>>>>2:%s", __func__);
}
+ (void)catClassMethod {
    NSLog(@"~~cat class method~~");
}
@end

Cat+YYAdd.h

@interface Cat (YYAdd)
@property (nonatomic, assign) float weight;
- (void)jump;
@end

Cat+YYAdd.m

@implementation Cat (YYAdd)

- (void)setWeight:(float)weight {
    objc_setAssociatedObject(self, @selector(weight), @(weight), OBJC_ASSOCIATION_ASSIGN);
}

- (float)weight {
    return [objc_getAssociatedObject(self, _cmd) floatValue];
}

- (void)jump {
    NSLog(@"~~Cat jump~~");
}
@end

Runtime Demo

class部分

// 获取类名
const char *className = class_getName(Cat.class);
NSLog(@"%@", [NSString stringWithUTF8String:className]);
// 结果: Cat

// 获取父类
Class superClass = class_getSuperclass(Cat.class);
NSLog(@"%@", superClass);
// 结果: NSObject

// 该函数的作用是获取类的实例所占用内存的大小
size_t instanceSizeOfClass = class_getInstanceSize(Cat.class);
NSLog(@"%zu", instanceSizeOfClass);
// 结果: 24

// 获取实例变量
Ivar ivar = class_getInstanceVariable(Cat.class, "_color");
NSLog(@"%@", [NSString stringWithUTF8String:ivar_getName(ivar)]);
// 结果: _color
    
// 获取属性
objc_property_t prop = class_getProperty(Cat.class, "name");
NSLog(@"%@", [NSString stringWithUTF8String:property_getName(prop)]);
// 结果: name

// 获取实例方法的实现, 并执行
IMP mewImp = class_getMethodImplementation(Cat.class, @selector(mew));
mewImp();
// 结果: -----喵-----

// 获取类的所有实例
unsigned int ivarListCount = 0;
Ivar *ivars = class_copyIvarList(Cat.class, &ivarListCount);
for (NSInteger i = 0; i < ivarListCount; i++) {
   Ivar ivar = ivars[i];
   const char *name = ivar_getName(ivar);
   NSLog(@"ivarList: %@", [NSString stringWithUTF8String:name]);
}
free(ivars);
// 结果: 
ivarList: _color
ivarList: _name

// 获取类的所有属性
unsigned int propertyListCount = 0;
objc_property_t *props = class_copyPropertyList(Cat.class, &propertyListCount);
for (NSInteger i = 0; i < propertyListCount; i++) {
   objc_property_t property = props[i];
   const char *name = property_getName(property);
   NSLog(@"propertyList: %@", [NSString stringWithUTF8String:name]);
}
free(props);
// 结果: 
propertyList: weight
propertyList: name
// 由此可见, 运行时添加的关联属性, 没有生成实例

// 获取类的所有实例方法
unsigned int methodListCount = 0;
Method *methods = class_copyMethodList(Cat.class, &methodListCount);
for (NSInteger i = 0; i < methodListCount; i++) {
   Method method = methods[i];
   SEL name = method_getName(method);
   NSLog(@"methodList: %@", NSStringFromSelector(name));
}
free(methods);
// 结果: 
methodList: mew
methodList: method0:agu1:agu2:agu3:agu4:
methodList: method0
methodList: method1
methodList: method2
methodList: init
methodList: .cxx_destruct
methodList: name
methodList: setName:
methodList: run
methodList: jump
methodList: setWeight:
methodList: weight

// 获取类所遵守的协议
unsigned int protocolListCount = 0;
Protocol * __unsafe_unretained *protocols = class_copyProtocolList(Cat.class, &protocolListCount);
for (NSInteger i = 0; i < protocolListCount; i++) {
   Protocol *protocal = protocols[i];
   const char *name = protocol_getName(protocal);
   NSLog(@"protocolList: %@", [NSString stringWithUTF8String:name]);
}
free(protocols);
// 结果: protocolList: Movable
    
// 获取类的某个类方法
Method classMethod = class_getClassMethod(Cat.class, NSSelectorFromString(@"catClassMethod"));
SEL classMethodName = method_getName(classMethod);
NSLog(@"clasMethod: %@", NSStringFromSelector(classMethodName));
IMP classMethodNameIMP = method_getImplementation(classMethod);
classMethodNameIMP();
// 结果: clasMethod: catClassMethod

// 获取类的元类
Class metaClass = objc_getMetaClass("Cat");
NSLog(@"meta class: %@", metaClass);
// 结果: meta class: Cat
    
// 从元类中获取所有类方法
unsigned int metaMethodListCount = 0;
Method *metaMethods = class_copyMethodList(metaClass, &metaMethodListCount);
for (NSInteger i = 0; i < metaMethodListCount; i++) {
   Method method = metaMethods[i];
   SEL name = method_getName(method);
   NSLog(@"metaMethodList: %@", NSStringFromSelector(name));
}
free(metaMethods);
// 结果: 
metaMethodList: mews
metaMethodList: catClassMethod
// 证明类方法的确存放在元类中

其他api

// 获取isa指向的Class
Class object_getClass(id obj)

// 设置isa指向的Class
Class object_setClass(id obj, Class cls)

// 判断一个OC对象是否为Class
BOOL object_isClass(id obj)

// 判断一个Class是否为元类
BOOL class_isMetaClass(Class cls)

object部分

Cat *cat = Cat.new;
cat.name = @"小麻烦";
cat.weight = 5.0;
    
NSLog(@"cat weight: %@", @(cat.weight)); // cat weight: 5
objc_removeAssociatedObjects(cat);
NSLog(@"cat weight after remove: %@", @(cat.weight)); // cat weight after remove: 0
    
Ivar ivar = class_getInstanceVariable(Cat.class, "_color");
NSLog(@"internal instance old value: %@", object_getIvar(cat, ivar)); // internal instance old value: Generic Gray Gamma 2.2 Profile colorspace 0 1
object_setIvar(cat, ivar, [NSColor orangeColor]);
NSLog(@"internal instance new value: %@", object_getIvar(cat, ivar)); // internal instance new value: sRGB IEC61966-2.1 colorspace 1 0.5 0 1

动态创建一个类

// C语言实现得getter
NSString *personNameGetter(id classInstance, SEL _cmd) {
    Ivar ivar = class_getInstanceVariable([classInstance class], "_name");
    return object_getIvar(classInstance, ivar);
}
// C语言实现得setter
void personNameSetter(id classInstance, SEL _cmd, NSString *newName) {
    Ivar ivar = class_getInstanceVariable([classInstance class], "_name");
    id oldName = object_getIvar(classInstance, ivar);
    if (oldName != newName) object_setIvar(classInstance, ivar, [newName copy]);
}

//下面对应的编码值可以在官方文档里面找到
    //编码值     含意
    //c     代表char类型
    //i     代表int类型
    //s     代表short类型
    //l     代表long类型，在64位处理器上也是按照32位处理
    //q     代表long long类型
    //C     代表unsigned char类型
    //I     代表unsigned int类型
    //S     代表unsigned short类型
    //L     代表unsigned long类型
    //Q     代表unsigned long long类型
    //f     代表float类型
    //d     代表double类型
    //B     代表C++中的bool或者C99中的_Bool
    //v     代表void类型
    //*     代表char *类型
    //@     代表对象类型
    //#     代表类对象 (Class)
    //:     代表方法selector (SEL)
    //[array type]     代表array
    //{name=type…}     代表结构体
    //(name=type…)     代表union
    //bnum     A bit field of num bits
    //^type     A pointer to type
    //?     An unknown type (among other things, this code is used for function pointers)
    
    Class PersonClass = objc_allocateClassPair(NSObject.class, "Person", 0);
    // 添加属性必须在objc_allocateClassPair和objc_registerClassPair之间
    BOOL result = class_addIvar(PersonClass,
                                "_gender",
                                sizeof(NSString *),
                                log2(sizeof(NSString *)),
                                "@");
    
    BOOL result2 = class_addIvar(PersonClass,
                                "_name",
                                sizeof(NSString *),
                                log2(sizeof(NSString *)),
                                "@");
    // 也可以将 "@" 用@encode(NSString)表示
    
    if (result && result2) {
        objc_registerClassPair(PersonClass);
    }
    else {
        objc_disposeClassPair(PersonClass);
    }
    
    // https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtPropertyIntrospection.html
    // 结合文档, 添加属性需以T开头, V结尾
    objc_property_attribute_t type = {"T", "@\"NSString\""};
    objc_property_attribute_t ownership = {"C", ""};
    objc_property_attribute_t nonatomic = {"N", ""};
    objc_property_attribute_t backingIvar = {"V", "_name"};
    objc_property_attribute_t attrs[] = {type, ownership, nonatomic, backingIvar};
    class_addProperty(PersonClass, "name", attrs, 4);
    
    SEL getter = NSSelectorFromString(@"name");
    SEL setter = NSSelectorFromString(@"setName:");
    // 添加方法
    class_addMethod(PersonClass, getter, (IMP)personNameGetter, "@@:"); // or use method_getTypeEncoding for last argument
    class_addMethod(PersonClass, setter, (IMP)personNameSetter, "v@:@");
    

// 以下为测试该类
    Ivar ivar = class_getInstanceVariable(PersonClass, "_gender");
    NSLog(@"Person ivar:%@",[NSString stringWithUTF8String:ivar_getName(ivar)]);
    // 结果: Person ivar:_gender
    
    
    objc_property_t prop = class_getProperty(PersonClass, "name");
    NSLog(@"Person property:%@",[NSString stringWithUTF8String:property_getName(prop)]);
    // 结果: Person property:name
    
    
    Method method = class_getInstanceMethod(PersonClass, NSSelectorFromString(@"setName:"));
    NSLog(@"%@", NSStringFromSelector(method_getName(method)));
    // 结果: setName:
    
    id person = [PersonClass new];
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
    [person performSelector:setter withObject:@"Phoenix"];
    NSLog(@"person name get:%@", [person performSelector:getter withObject:nil]);
#pragma clang diagnostic pop
// 结果: person name get:Phoenix

方法部分

void newCatMethod() {
    NSLog(@"~~汪~~");
}

void replaceMethod() {
    class_replaceMethod(Cat.class, @selector(mew), (IMP)newCatMethod, NULL);
    IMP mew = class_getMethodImplementation(Cat.class, @selector(mew));
    mew();
    // 结果: ~~汪~~
}

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wundeclared-selector"
    Method method = class_getInstanceMethod(Cat.class, @selector(method0:agu1:agu2:agu3:agu4:));
#pragma clang diagnostic pop
    
    SEL methodName = method_getName(method);
    NSLog(@"%@", NSStringFromSelector(methodName));
    // 结果: method0:agu1:agu2:agu3:agu4:
    
    IMP methodIMP = method_getImplementation(method);
#pragma unused(methodIMP)
    
    const char *attrs = method_getTypeEncoding(method);
    NSLog(@"%@", [NSString stringWithUTF8String:attrs]);
    // 结果: @80@0:8@16d24@32@40{CGRect={CGPoint=dd}{CGSize=dd}}48
    
    unsigned int count = method_getNumberOfArguments(method);
    NSLog(@"%u", count);
    // 结果: 7 因为还有self 和 _cmd
    
    for (unsigned int i =0 ; i < count; i++) {
        char result[1024] = {};
        method_getArgumentType(method, i, result, 1024);
        NSLog(@"类型是 %s", result);
    }
    
    char returnType[1024] = {};
    method_getReturnType(method, returnType, 1024);
    NSLog(@"return type:%s",returnType);
    
    struct objc_method_description result7 = *method_getDescription(method);
    NSLog(@"description ~%@ ~%@",NSStringFromSelector(result7.name),[NSString stringWithUTF8String:result7.types]);

其他API

char method_copyReturnType(Method m)
char method_copyArgumentType(Method m, unsigned int index)

// 选择器相关
const char sel_getName(SEL sel)
SEL sel_registerName(const char str)

// 用block作为方法实现
IMP imp_implementationWithBlock(id block)
id imp_getBlock(IMP anImp)
BOOL imp_removeBlock(IMP anImp)

交换方法

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wundeclared-selector"
    Method result0 = class_getInstanceMethod(Cat.class, @selector(method0));
    Method result1 = class_getInstanceMethod(Cat.class, @selector(method1));
    Method result2 = class_getInstanceMethod(Cat.class, @selector(method2));
    method_setImplementation(result0, method_getImplementation(result1));
    
    method_getImplementation(result0)();
    
    method_exchangeImplementations(result0, result2);
    
    method_getImplementation(result0)();
    method_getImplementation(result2)();
#pragma clang diagnostic pop

// 结果:  
>>>>>>>>1:-[Cat method1]
>>>>>>>>2:-[Cat method2]
>>>>>>>>1:-[Cat method1]