Objective-C Runtime 运行时之一：类与对象

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];

meta-class是一个类对象的类。

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 );

// 获取类中指定名称实例成员变量的信息
Ivar class_getInstanceVariable ( Class cls, const char *name );
// 获取类成员变量的信息
Ivar class_getClassVariable ( Class cls, const char *name );
// 添加成员变量
BOOL class_addIvar ( Class cls, const char *name, size_t size, uint8_t alignment, const char *types );
// 获取整个成员变量列表
Ivar * class_copyIvarList ( Class cls, unsigned int *outCount );

// 获取指定的属性
objc_property_t class_getProperty ( Class cls, const char *name );
// 获取属性列表
objc_property_t * class_copyPropertyList ( Class cls, unsigned int *outCount );
// 为类添加属性
BOOL class_addProperty ( Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount );
// 替换类的属性
void class_replaceProperty ( Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount );

const uint8_t * class_getIvarLayout ( Class cls );
void class_setIvarLayout ( Class cls, const uint8_t *layout );
const uint8_t * class_getWeakIvarLayout ( Class cls );
void class_setWeakIvarLayout ( Class cls, const uint8_t *layout );

// 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 );

#import <Foundation/Foundation.h>
@interface MyClass : NSObject <NSCopying, NSCoding>
@property (nonatomic, strong) NSArray *array;
@property (nonatomic, copy) NSString *string;
- (void)method1;
- (void)method2;
+ (void)classMethod1;
@end

#import "MyClass.h"
@interface MyClass () {
    NSInteger _instance1;
    NSString *_instance2;
}
@property (nonatomic, assign) NSInteger integer;
- (void)method3WithArg1:(NSInteger)arg1 arg2:(NSString *)arg2;
@end
@implementation MyClass
+ (void)classMethod1 {
	NSLog(@"调用类方法 classMethod1");
}
- (void)method1 {
    NSLog(@"调用实例方法 method1");
}
- (void)method2 {
	NSLog(@"调用实例方法 method2");
}
- (void)method3WithArg1:(NSInteger)arg1 arg2:(NSString *)arg2 {
    NSLog(@"arg1 : %ld, arg2 : %@",arg1,arg2);
}
@end

#import "ViewController.h"
#import <objc/runtime.h>
#import "MyClass.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event {
    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(@"---------------------------------");
    
    //元类
    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);
    //指定名称的成员变量
    Ivar string = class_getInstanceVariable(cls, "_string");
    if (string != NULL) {
        NSLog(@"instanve 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);
    //指定名称的属性
    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);
    //指定方法名实例方法
    Method method1 = class_getInstanceMethod(cls, @selector(method1));
    if (method1 != NULL) {
        NSLog(@"instance method: %s ",method_getName(method1));
    }
    //指定方法名类方法
    Method classMethod = class_getClassMethod(cls, @selector(classMethod1));
    if (classMethod != NULL) {
        NSLog(@"class method :%s",method_getName(classMethod));
    }
    //判断是否实现某方法
    NSLog(@"MyClass is %@ responsd to selector: method3WithArg1:arg2:",class_respondsToSelector(cls, @selector(method3WithArg1:arg2:))?@"":@"not");
    NSLog(@"---------------------------------");
    
    //获取指定方法实现
    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(@"---------------------------------");
   
}
@end

// 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);
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 );

id theObject = class_createInstance(NSString.class, sizeof(unsigned));
 
id str1 = [theObject init];
NSLog(@"%@", [str1 class]);
id str2 = [[NSString alloc] initWithString:@"test"];
NSLog(@"%@", [str2 class]);

2014-10-23 12:46:50.781 RuntimeTest[4039:89088] NSString
2014-10-23 12:46:50.781 RuntimeTest[4039:89088] __NSCFConstantString

// 返回指定对象的一份拷贝
id object_copy ( id obj, size_t size );
// 释放指定对象占用的内存
id object_dispose ( id obj );

NSObject *a = [[NSObject alloc] init];
id newB = object_copy(a, class_getInstanceSize(MyClass.class));
object_setClass(newB, MyClass.class);
object_dispose(a);

// 修改类实例的实例变量的值
Ivar object_setInstanceVariable ( id obj, const char *name, void *value );
// 获取对象实例变量的值
Ivar object_getInstanceVariable ( id obj, const char *name, void **outValue );
// 返回指向给定对象分配的任何额外字节的指针
void * object_getIndexedIvars ( id obj );
// 返回对象中实例变量的值
id object_getIvar ( id obj, Ivar ivar );
// 设置对象中实例变量的值
void object_setIvar ( id obj, Ivar ivar, id value );

// 返回给定对象的类名
const char * object_getClassName ( id obj );
// 返回对象的类
Class object_getClass ( id obj );
// 设置对象的类
Class object_setClass ( id obj, Class cls );

// 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;
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);
}

2014-10-23 16:20:52.589 RuntimeTest[8437:188589] number of classes: 1282
2014-10-23 16:20:52.589 RuntimeTest[8437:188589] class name: DDTokenRegexp
2014-10-23 16:20:52.590 RuntimeTest[8437:188589] class name: _NSMostCommonKoreanCharsKeySet
2014-10-23 16:20:52.590 RuntimeTest[8437:188589] class name: OS_xpc_dictionary
2014-10-23 16:20:52.590 RuntimeTest[8437:188589] class name: NSFileCoordinator
2014-10-23 16:20:52.590 RuntimeTest[8437:188589] class name: NSAssertionHandler
2014-10-23 16:20:52.590 RuntimeTest[8437:188589] class name: PFUbiquityTransactionLogMigrator
2014-10-23 16:20:52.591 RuntimeTest[8437:188589] class name: NSNotification
2014-10-23 16:20:52.591 RuntimeTest[8437:188589] class name: NSKeyValueNilSetEnumerator
2014-10-23 16:20:52.591 RuntimeTest[8437:188589] class name: OS_tcp_connection_tls_session
2014-10-23 16:20:52.591 RuntimeTest[8437:188589] class name: _PFRoutines
......还有大量输出