Objective-C Runtime详解

typedef struct objc_class *Class;

struct objc_class {
    Class isa  OBJC_ISA_AVAILABILITY;

#if !__OBJC2__
    Class super_class                       OBJC2_UNAVAILABLE;  // 父类
    const char *name                        OBJC2_UNAVAILABLE;  // 类名
    long version                            OBJC2_UNAVAILABLE;  // 类的版本信息，默认为0
    long info                               OBJC2_UNAVAILABLE;  // 类信息，供运行期使用的一些位标识
    long instance_size                      OBJC2_UNAVAILABLE;  // 该类的实例变量大小
    struct objc_ivar_list *ivars            OBJC2_UNAVAILABLE;  // 该类的成员变量链表
    struct objc_method_list **methodLists   OBJC2_UNAVAILABLE;  // 方法定义的链表
    struct objc_cache *cache                OBJC2_UNAVAILABLE;  // 方法缓存
    struct objc_protocol_list *protocols    OBJC2_UNAVAILABLE;  // 协议链表
#endif

} OBJC2_UNAVAILABLE;

NSArray *array = [[NSArray alloc] init];

struct objc_object {
    Class isa  OBJC_ISA_AVAILABILITY;
};

typedef struct objc_object *id;

struct objc_cache {
    unsigned int mask /* total = mask + 1 */                 OBJC2_UNAVAILABLE;
    unsigned int occupied                                    OBJC2_UNAVAILABLE;
    Method buckets[1]                                        OBJC2_UNAVAILABLE;
};

NSArray *array = [NSArray array];

void TestMetaClass(id self, SEL _cmd) {

    NSLog(@"This objcet is %p", self);
    NSLog(@"Class is %@, super class is %@", [self class], [self superclass]);

    Class currentClass = [self class];
    for (int i = 0; i < 4; i++) {
        NSLog(@"Following the isa pointer %d times gives %p", i, currentClass);
        currentClass = objc_getClass((__bridge void *)currentClass);
    }

    NSLog(@"NSObject's class is %p", [NSObject class]);
    NSLog(@"NSObject's meta class is %p", objc_getClass((__bridge void *)[NSObject class]));
}

#pragma mark -

@implementation Test

- (void)ex_registerClassPair {

    Class newClass = objc_allocateClassPair([NSError class], "TestClass", 0);
    class_addMethod(newClass, @selector(testMetaClass), (IMP)TestMetaClass, "v@:");
    objc_registerClassPair(newClass);

    id instance = [[newClass alloc] initWithDomain:@"some domain" code:0 userInfo:nil];
    [instance performSelector:@selector(testMetaClass)];
}

@end

// 获取类的类名
const char * class_getName ( Class cls );

// 获取类的父类
Class class_getSuperclass ( Class cls );
// 判断给定的Class是否是一个元类
BOOL class_isMetaClass ( Class cls );

// 获取实例大小
size_t class_getInstanceSize ( Class cls );

// 添加方法
BOOL class_addMethod ( Class cls, SEL name, IMP imp, const char *types );
// 获取实例方法
Method class_getInstanceMethod ( Class cls, SEL name );
// 获取类方法
Method class_getClassMethod ( Class cls, SEL name );
// 获取所有方法的数组
Method * class_copyMethodList ( Class cls, unsigned int *outCount );
// 替代方法的实现
IMP class_replaceMethod ( Class cls, SEL name, IMP imp, const char *types );
// 返回方法的具体实现
IMP class_getMethodImplementation ( Class cls, SEL name );
IMP class_getMethodImplementation_stret ( Class cls, SEL name );
// 类实例是否响应指定的selector
BOOL class_respondsToSelector ( Class cls, SEL sel );

// 添加协议
BOOL class_addProtocol ( Class cls, Protocol *protocol );
// 返回类是否实现指定的协议
BOOL class_conformsToProtocol ( Class cls, Protocol *protocol );
// 返回类实现的协议列表
Protocol * class_copyProtocolList ( Class cls, unsigned int *outCount );

// 获取版本号
int class_getVersion ( Class cls );
// 设置版本号
void class_setVersion ( Class cls, int version );

Class objc_getFutureClass ( const char *name );
void objc_setFutureClass ( Class cls, const char *name );

//-----------------------------------------------------------
// MyClass.h
@interface MyClass : NSObject <NSCopying, NSCoding>
@property (nonatomic, strong) NSArray *array;
@property (nonatomic, copy) NSString *string;
- (void)method1;
- (void)method2;
+ (void)classMethod1;
@end
//-----------------------------------------------------------
// MyClass.m
#import "MyClass.h"
@interface MyClass () {
    NSInteger       _instance1;
    NSString    *   _instance2;
}
@property (nonatomic, assign) NSUInteger integer;
- (void)method3WithArg1:(NSInteger)arg1 arg2:(NSString *)arg2;
@end
@implementation MyClass
+ (void)classMethod1 {
}
- (void)method1 {
    NSLog(@"call method method1");
}
- (void)method2 {
}
- (void)method3WithArg1:(NSInteger)arg1 arg2:(NSString *)arg2 {
    NSLog(@"arg1 : %ld, arg2 : %@", arg1, arg2);
}
@end
//-----------------------------------------------------------
// main.h
#import "MyClass.h"
#import "MySubClass.h"
#import <objc/runtime.h>
int main(int argc, const char * argv[]) {
    @autoreleasepool {
    
        MyClass *myClass = [[MyClass alloc] init];
        unsigned int outCount = 0;
        Class cls = myClass.class;
        // 类名
        NSLog(@"class name: %s", class_getName(cls));
        NSLog(@"==========================================================");
        // 父类
        NSLog(@"super class name: %s", class_getName(class_getSuperclass(cls)));
        NSLog(@"==========================================================");
        // 是否是元类
        NSLog(@"MyClass is %@ a meta-class", (class_isMetaClass(cls) ? @"" : @"not"));
        NSLog(@"==========================================================");
      // 上一个例子中使用objc_getClass()获取isa以获得meta class
        Class meta_class = objc_getMetaClass(class_getName(cls));
        NSLog(@"%s's meta-class is %s", class_getName(cls), class_getName(meta_class));
        NSLog(@"==========================================================");
        // 变量实例大小
        NSLog(@"instance size: %zu", class_getInstanceSize(cls));
        NSLog(@"==========================================================");
        // 成员变量
        Ivar *ivars = class_copyIvarList(cls, &outCount);
        for (int i = 0; i < outCount; i++) {
            Ivar ivar = ivars[i];
            NSLog(@"instance variable's name: %s at index: %d", ivar_getName(ivar), i);
        }
        free(ivars);
        Ivar string = class_getInstanceVariable(cls, "_string");
        if (string != NULL) {
            NSLog(@"instace variable %s", ivar_getName(string));
        }
        NSLog(@"==========================================================");
        // 属性操作
        objc_property_t * properties = class_copyPropertyList(cls, &outCount);
        for (int i = 0; i < outCount; i++) {
            objc_property_t property = properties[i];
            NSLog(@"property's name: %s", property_getName(property));
        }
        free(properties);
        objc_property_t array = class_getProperty(cls, "array");
        if (array != NULL) {
            NSLog(@"property %s", property_getName(array));
        }
        NSLog(@"==========================================================");
        // 方法操作
        Method *methods = class_copyMethodList(cls, &outCount);
        for (int i = 0; i < outCount; i++) {
            Method method = methods[i];
            NSLog(@"method's signature: %s", method_getName(method));
        }
        free(methods);
        Method method1 = class_getInstanceMethod(cls, @selector(method1));
        if (method1 != NULL) {
            NSLog(@"method %s", method_getName(method1));
        }
        Method classMethod = class_getClassMethod(cls, @selector(classMethod1));
        if (classMethod != NULL) {
            NSLog(@"class method : %s", method_getName(classMethod));
        }
        NSLog(@"MyClass is%@ responsd to selector: method3WithArg1:arg2:", class_respondsToSelector(cls, @selector(method3WithArg1:arg2:)) ? @"" : @" not");
        IMP imp = class_getMethodImplementation(cls, @selector(method1));
        imp();
        NSLog(@"==========================================================");
        // 协议
        Protocol * __unsafe_unretained * protocols = class_copyProtocolList(cls, &outCount);
        Protocol * protocol;
        for (int i = 0; i < outCount; i++) {
            protocol = protocols[i];
            NSLog(@"protocol name: %s", protocol_getName(protocol));
        }
        NSLog(@"MyClass is%@ responsed to protocol %s", class_conformsToProtocol(cls, protocol) ? @"" : @" not", protocol_getName(protocol));
        NSLog(@"==========================================================");
    }
    return 0;
}

// 创建一个新类和元类
Class objc_allocateClassPair ( Class superclass, const char *name, size_t extraBytes );
// 销毁一个类及其相关联的类
void objc_disposeClassPair ( Class cls );
// 在应用中注册由objc_allocateClassPair创建的类
void objc_registerClassPair ( Class cls );

Class cls = objc_allocateClassPair(MyClass.class, "MySubClass", 0);

// imp_submethod1是一个已实现的C语言方法，用于规定新建的submethod1和method1的行为
class_addMethod(cls, @selector(submethod1), (IMP)imp_submethod1, "v@:");
class_replaceMethod(cls, @selector(method1), (IMP)imp_submethod1, "v@:");
class_addIvar(cls, "_ivar1", sizeof(NSString *), log(sizeof(NSString *)), "i");

objc_property_attribute_t type = {"T", "@\"NSString\""};
objc_property_attribute_t ownership = { "C", "" };
objc_property_attribute_t backingivar = { "V", "_ivar1"};
objc_property_attribute_t attrs[] = {type, ownership, backingivar};

class_addProperty(cls, "property2", attrs, 3);
objc_registerClassPair(cls);

id instance = [[cls alloc] init];
[instance performSelector:@selector(submethod1)];
[instance performSelector:@selector(method1)];

// 创建类实例
id class_createInstance ( Class cls, size_t extraBytes );
// 在指定位置创建类实例
id objc_constructInstance ( Class cls, void *bytes );
// 销毁类实例
void * objc_destructInstance ( id obj );

// 获取已注册的类定义的列表
int objc_getClassList ( Class *buffer, int bufferCount );
// 创建并返回一个指向所有已注册类的指针列表
Class* objc_copyClassList ( unsigned int *outCount );
// 返回指定类的类定义
Class objc_lookUpClass ( const char *name );
Class objc_getClass ( const char *name );
Class objc_getRequiredClass ( const char *name );
// 返回指定类的元类
Class objc_getMetaClass ( const char *name );

int numClasses;
Class * classes = NULL;
// 首先检测已注册的类的数量是否大于0
numClasses = objc_getClassList(NULL, 0);
if (numClasses > 0) {
    classes = malloc(sizeof(Class) * numClasses);
    numClasses = objc_getClassList(classes, numClasses);
    NSLog(@"number of classes: %d", numClasses);
    for (int i = 0; i < numClasses; i++) {
        Class cls = classes[i];
        NSLog(@"class name: %s", class_getName(cls));
  }
    free(classes);
}

float a[] = {1.0, 2.0, 3.0};
NSLog(@"array encoding type: %s", @encode(typeof(a)));

typedef struct objc_ivar *Ivar;
struct objc_ivar {
    char *ivar_name               OBJC2_UNAVAILABLE;// 变量名
    char *ivar_type             OBJC2_UNAVAILABLE;// 变量类型
    int ivar_offset            OBJC2_UNAVAILABLE;// 基地址偏移字节
#ifdef __LP64__
    int space                 OBJC2_UNAVAILABLE;
#endif
}

typedef struct objc_property *objc_property_t;

typedef struct {
    const char *name;           // 特性名
    const char *value;          // 特性值
} objc_property_attribute_t;

static char myKey;
objc_setAssociatedObject(self, &myKey, anObject, OBJC_ASSOCIATION_RETAIN);

id anObject = objc_getAssociatedObject(self, &myKey);

- (void)setTapActionWithBlock:(void (^)(void))block
{
UITapGestureRecognizer *gesture = objc_getAssociatedObject(self, &kDTActionHandlerTapGestureKey);
 
if (!gesture)
{
gesture = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(__handleActionForTapGesture:)];
[self addGestureRecognizer:gesture];
objc_setAssociatedObject(self, &kDTActionHandlerTapGestureKey, gesture, OBJC_ASSOCIATION_RETAIN);
}
objc_setAssociatedObject(self, &kDTActionHandlerTapBlockKey, block, OBJC_ASSOCIATION_COPY);
}

- (void)__handleActionForTapGesture:(UITapGestureRecognizer *)gesture
{
if (gesture.state == UIGestureRecognizerStateRecognized)
{
void(^action)(void) = objc_getAssociatedObject(self, &kDTActionHandlerTapBlockKey);
if (action)
{
action();
}
}
}

@interface MyViewController :UIViewController {
    UIButton *myButton; // 成员变量
}
@property (nonatomic, retain) UIButton *myButton; // 属性
@end

@interface MyViewController :UIViewController
@property (nonatomic, retain) UIButton *myButton;
@end

// 获取成员变量名
const char * ivar_getName ( Ivar v );
// 获取成员变量类型编码
const char * ivar_getTypeEncoding ( Ivar v );
// 获取成员变量的偏移量
ptrdiff_t ivar_getOffset ( Ivar v );

// 设置关联对象
void objc_setAssociatedObject ( id object, const void *key, id value, objc_AssociationPolicy policy );
// 获取关联对象
id objc_getAssociatedObject ( id object, const void *key );
// 移除关联对象
void objc_removeAssociatedObjects ( id object );

// 获取属性名
const char * property_getName ( objc_property_t property );
// 获取属性特性描述字符串
const char * property_getAttributes ( objc_property_t property );
// 获取属性中指定的特性
char * property_copyAttributeValue ( objc_property_t property, const char *attributeName );
// 获取属性的特性列表
objc_property_attribute_t * property_copyAttributeList ( objc_property_t property, unsigned int *outCount );

// MyObject.h
#import <Foundation/Foundation.h>

NS_ASSUME_NONNULL_BEGIN

@interface MyObject : NSObject

@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *status;

- (NSString *)propertyForKey: (NSString *)key;
- (void)setDataWithDic:(NSDictionary *)dic;

@end

NS_ASSUME_NONNULL_END

@{@"name1": @"张三", @"status1": @"start"}
@{@"name2": @"张三", @"status2": @"end"}

// MyObject.m
#import "MyObject.h"
#import <objc/runtime.h>

static NSMutableDictionary *map = nil;

@implementation MyObject

+ (void)load {
    map = [NSMutableDictionary dictionary];
    map[@"name1"] = @"name";
    map[@"status1"] = @"status";
    map[@"name2"] = @"name";
    map[@"status2"] = @"status";
}

- (NSString *)propertyForKey:(NSString *)key {
    if (map == nil) {
        [MyObject load];
    }
    return map[key];
}

// 上面的代码将两个字典中不同的字段映射到MyObject中相同的属性上，这样，转换方法可如下处理
- (void)setDataWithDic:(NSDictionary *)dic {
    [dic enumerateKeysAndObjectsUsingBlock:^(NSString *key, id obj, BOOL *stop) {
        NSString *propertyKey = [self propertyForKey: key];
        NSLog(@"propertyKey: %@", propertyKey);
        
        if (propertyKey) {
            objc_property_t property = class_getProperty([self class], [propertyKey UTF8String]);
            NSString *attributeString = [NSString stringWithCString:property_getAttributes(property) encoding:NSUTF8StringEncoding];
            NSLog(@"attributeString: %@", attributeString);
            // ...
            [self setValue:obj forKey:propertyKey];
        }
    }];
}

@end

// main.m
#import <Foundation/Foundation.h>
#import "MyObject.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        MyObject *myObject = [[MyObject alloc] init];
        [myObject setDataWithDic:@{@"name1": @"张三", @"status1": @"start"}];
        // load data from myObject
        NSLog(@"myObject name: %@, status: %@", myObject.name, myObject.status);
    }
    return 0;
}

typedef struct objc_selector *SEL;

SEL sel1 = @selector(method1);
NSLog(@"sel : %p", sel1);

- (void)setWidth:(int)width;
- (void)setWidth:(double)width;

-(void)setWidthIntValue:(int)width;
-(void)setWidthDoubleValue:(double)width;

id (*IMP)(id, SEL, ...)

typedef struct objc_method *Method;

struct objc_method {
    SEL method_name                OBJC2_UNAVAILABLE;// 方法名
    char *method_types              OBJC2_UNAVAILABLE;
    IMP method_imp             OBJC2_UNAVAILABLE;// 方法实现
}

struct objc_method_description { SEL name; char *types; };

// 调用指定方法的实现
id method_invoke ( id receiver, Method m, ... );
// 调用返回一个数据结构的方法的实现
void method_invoke_stret ( id receiver, Method m, ... );
// 获取方法名
SEL method_getName ( Method m );
// 返回方法的实现
IMP method_getImplementation ( Method m );
// 获取描述方法参数和返回值类型的字符串
const char * method_getTypeEncoding ( Method m );
// 获取方法的返回值类型的字符串
char * method_copyReturnType ( Method m );
// 获取方法的指定位置参数的类型字符串
char * method_copyArgumentType ( Method m, unsigned int index );
// 通过引用返回方法的返回值类型字符串
void method_getReturnType ( Method m, char *dst, size_t dst_len );
// 返回方法的参数的个数
unsigned int method_getNumberOfArguments ( Method m );
// 通过引用返回方法指定位置参数的类型字符串
void method_getArgumentType ( Method m, unsigned int index, char *dst, size_t dst_len );
// 返回指定方法的方法描述结构体
struct objc_method_description * method_getDescription ( Method m );
// 设置方法的实现
IMP method_setImplementation ( Method m, IMP imp );
// 交换两个方法的实现
void method_exchangeImplementations ( Method m1, Method m2 );

// 返回给定选择器指定的方法的名称
const char * sel_getName ( SEL sel );
// 在Objective-C Runtime系统中注册一个方法，将方法名映射到一个选择器，并返回这个选择器
SEL sel_registerName ( const char *str );
// 在Objective-C Runtime系统中注册一个方法
SEL sel_getUid ( const char *str );
// 比较两个选择器
BOOL sel_isEqual ( SEL lhs, SEL rhs );

objc_msgSend(receiver, selector)

objc_msgSend(receiver, selector, arg1, arg2, ...)

- strange
{
    id  target = getTheReceiver();
    SEL method = getTheMethod();

    if ( target == self || method == _cmd )
        return nil;

    return [target performSelector:method];
}

void (*setter)(id, SEL, BOOL);
int i;

setter = (void (*)(id, SEL, BOOL))[target methodForSelector:@selector(setFilled:)];

for (i = 0 ; i < 1000 ; i++)
    setter(targetList[i], @selector(setFilled:), YES);

if ([self respondsToSelector:@selector(method)]) {
    [self performSelector:@selector(method)];
}

void functionForMethod1(id self, SEL _cmd) {
   NSLog(@"%@, %p", self, _cmd);
}

+ (BOOL)resolveInstanceMethod:(SEL)sel {

    NSString *selectorString = NSStringFromSelector(sel);
    if ([selectorString isEqualToString:@"method1"]) {
        class_addMethod(self.class, @selector(method1), (IMP)functionForMethod1, "@:");
    }

    return [super resolveInstanceMethod:sel];
}

// call method1 by performSelector
[self performSelector:@selector(method1)]

- (id)forwardingTargetForSelector:(SEL)aSelector

// SUTRuntimeMethod.h
#import <Foundation/Foundation.h>

@interface SUTRuntimeMethod : NSObject

+ (instancetype)object;
- (void)test;

@end

// SUTRuntimeMethod.m
#import "SUTRuntimeMethod.h"


@interface SUTRuntimeMethodHelper: NSObject

- (void)method2;

@end

@implementation SUTRuntimeMethodHelper

- (void)method2 {
    NSLog(@"self: %@, sel: %p", self, _cmd);
}

@end

#pragma mark - SUTRuntimeMethod

@interface SUTRuntimeMethod () {
    SUTRuntimeMethodHelper *_helper;
}
@end

@implementation SUTRuntimeMethod

+ (instancetype)object {
    return [[self alloc] init];
}

- (instancetype)init {
    self = [super init];
    if (self != nil) {
        _helper = [[SUTRuntimeMethodHelper alloc] init];
    }
    return self;
}

- (void)test {
    [self performSelector:@selector(method2)];
}

- (id)forwardingTargetForSelector:(SEL)aSelector {
    NSLog(@"forwardingTargetForSelector");

    NSString *selectorString = NSStringFromSelector(aSelector);
    if ([selectorString isEqualToString:@"method2"]) {
        return _helper;
    }

    return [super forwardingTargetForSelector:aSelector];
}

@end

// main.m
#import <Foundation/Foundation.h>
#import "SUTRuntimeMethod.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        SUTRuntimeMethod *method = [SUTRuntimeMethod object];
        [method test];
    }
    return 0;
}

- (void)forwardInvocation:(NSInvocation *)anInvocation

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector

- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {

    NSMethodSignature *signature = [super methodSignatureForSelector:aSelector];
    if (!signature) {
        if ([SUTRuntimeMethodHelper instancesRespondToSelector:aSelector]) {
            signature = [SUTRuntimeMethodHelper instanceMethodSignatureForSelector:aSelector];
        }
    }

    return signature;
}

- (void)forwardInvocation:(NSInvocation *)anInvocation {
    if ([SUTRuntimeMethodHelper instancesRespondToSelector:anInvocation.selector]) {
        [anInvocation invokeWithTarget:_helper];
    }
}

- (BOOL)respondsToSelector:(SEL)aSelector
{
if ( [super respondsToSelector:aSelector])
return YES;
else {
/* Here, test whether the aSelector message can     *
 * be forwarded to another object and whether that  *
 * object can respond to it. Return YES if it can.  */
}

return NO; 
}