iOS-RunTime

/// An opaque type that represents a method in a class definition. 一个类型，代表着类定义中的一个方法
typedef struct objc_method *Method;

/// An opaque type that represents an instance variable.代表实例(对象)的变量
typedef struct objc_ivar *Ivar;

/// An opaque type that represents a category.代表一个分类
typedef struct objc_category *Category;

/// An opaque type that represents an Objective-C declared property.代表OC声明的属性
typedef struct objc_property *objc_property_t;

// Class代表一个类，它在objc.h中这样定义的 typedef struct objc_class *Class;
struct objc_class {
Class isa OBJC_ISA_AVAILABILITY;

#if !__OBJC2__
Class super_class OBJC2_UNAVAILABLE;
const char *name OBJC2_UNAVAILABLE;
long version OBJC2_UNAVAILABLE;
long info OBJC2_UNAVAILABLE;
long instance_size OBJC2_UNAVAILABLE;
struct objc_ivar_list *ivars OBJC2_UNAVAILABLE;
struct objc_method_list **methodLists OBJC2_UNAVAILABLE;
struct objc_cache *cache OBJC2_UNAVAILABLE;
struct objc_protocol_list *protocols OBJC2_UNAVAILABLE;
#endif

} OBJC2_UNAVAILABLE; 

Class classPerson = Person.class;
// printf("%s\n", classPerson->name); //用这种方法已经不能获取name了 因为OBJC2_UNAVAILABLE
const char *cname = class_getName(classPerson);
printf("%s", cname); // 输出:Person

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    unsigned int count = 0;
    Class *classes = objc_copyClassList(&count);
    for (int i = 0; i < count; i++) {
        const char *cname = class_getName(classes[i]);
        printf("%s\n", cname);
    }
}

@interface Person : NSObject
{
    @private
    float _height;
}
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) int age;
@end

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {

Class classPerson = NSClassFromString(@"Person"); // 与下面一句效果一样,可以不用导入头文件
// Class clazz = Person.class;
unsigned int count = 0;
Ivar *ivarList = class_copyIvarList(classPerson, &count); // 获取成员变量数组
for (int i = 0; i < count; i++) {
const char *cname = ivar_getName(ivarList[i]); // 获取成员变量的名字
NSString *name = [NSString stringWithUTF8String:cname];
NSLog(@"%@", name);
}
NSLog(@"-------------------分割线------------------");
objc_property_t *propertyList = class_copyPropertyList(classPerson, &count); // 获取属性数组
for (int i = 0; i < count; i++) {
const char *cname = property_getName(propertyList[i]);
NSString *name = [NSString stringWithUTF8String:cname];
NSLog(@"%@", name);
}

}

2015-06-05 22:28:16.194 runtime终极[4192:195757] _height
2015-06-05 22:28:16.195 runtime终极[4192:195757] _age
2015-06-05 22:28:16.195 runtime终极[4192:195757] _name
2015-06-05 22:28:16.195 runtime终极[4192:195757] -------------------分割线------------------
2015-06-05 22:28:16.195 runtime终极[4192:195757] name
2015-06-05 22:28:16.195 runtime终极[4192:195757] age

Class clazz = Person.class;
unsigned int count = 0;

Person *person = [[Person alloc]init];
NSDictionary *dict = @{@"name":@"zhangsan",@"age":@19, @"height": @1.75};

Ivar *ivars = class_copyIvarList(clazz, &count);
// NSLog(@"%tu", count); // 3
for (int i = 0; i < count; i++) {
const char *cname = ivar_getName(ivars[i]);
NSString *name = [NSString stringWithUTF8String:cname];
NSString *key = [name substringFromIndex:1]; // 去掉‘_‘
[person setValue:dict[key] forKey:key];
}
NSLog(@"%@", person); // 已经重写了description方法 输出是：
<Person, 0x7ff15b80f230>{ name = zhangsan, height = 1.750000, age = 19}

Class clazz = Person.class;
unsigned int count = 0;

Person *person = [[Person alloc]init];
NSDictionary *dict = @{@"name":@"zhangsan",@"age":@19, @"height": @1.75};

Ivar *ivars = class_copyIvarList(clazz, &count);
for (int i = 0; i < count; i++) {
const char *cname = ivar_getName(ivars[i]);
NSString *name = [NSString stringWithUTF8String:cname];
NSString *key = [name substringFromIndex:1];

const char *coding = ivar_getTypeEncoding(ivars[i]); // 获取类型
NSString *strCode = [NSString stringWithUTF8String:coding];
id value = dict[key];
if ([strCode isEqualToString:@"f"]) {// 判断类型是否是float
value = @(0.0);
}

[person setValue:value forKey:key];
}
NSLog(@"%@", person); 这样就可以正常执行了，输出为：
<Person, 0x7fc75d004a00>{ name = zhangsan, height = 0.000000, age = 19}

- (void)encodeWithCoder:(NSCoder *)aCoder {
unsigned int count = 0;
Ivar *ivars = class_copyIvarList(self.class, &count);
for (int i = 0; i < count; i++) {
const char *cname = ivar_getName(ivars[i]);
NSString *name = [NSString stringWithUTF8String:cname];
NSString *key = [name substringFromIndex:1];

id value = [self valueForKey:key]; // 取出key对应的value
[aCoder encodeObject:value forKey:key]; // 编码
}
}
- (id)initWithCoder:(NSCoder *)aDecoder {
if (self = [super init]) {
unsigned int count = 0;
Ivar *ivars = class_copyIvarList(self.class, &count);
for (int i = 0; i < count; i++) {
const char *cname = ivar_getName(ivars[i]);
NSString *name = [NSString stringWithUTF8String:cname];
NSString *key = [name substringFromIndex:1];

id value = [aDecoder decodeObjectForKey:key]; // 解码
[self setValue:value forKey:key]; // 设置key对应的value
}
}
return self; 
}

// 程序一运行的时候调用
+ (void)load
{
// 如果是类方法，使用的是class_getClassMethod，如果是对象方法使用的是class_getInstanceMethod
Method methodOne = class_getInstanceMethod(self, @selector(methodOne:));
Method methodTwo = class_getInstanceMethod(self, @selector(methodTwo:));
// 交换两个方法的实现
method_exchangeImplementations(methodOne, methodTwo);
} 

// 交换前
- (NSString *) methodOne:(NSString *)str{
    NSLog(@"%@", [self methodTwo:str]);
    return "suc";
}
// 交换后 在方法的实现中，要注意将调用two的地方，换成自己的名字
- (NSString *) methodOne:(NSString *)str{
    NSLog(@"%@", [self methodOne:str]);
    return "suc";
}

const char* propertiesKey = "propertiesKey";
unsigned int count = 0;
Ivar *ivars = class_copyIvarList([Person class], &count);

NSMutableArray *arrayM = [NSMutableArray arrayWithCapacity:count];

for (unsigned int i = 0; i < count; ++i) {
    Ivar pty = ivars[i];
    const char *cname = ivar_getName(ivars[i]);
    NSString *name = [NSString stringWithUTF8String:cname];
    NSString *key = [name substringFromIndex:1]; // 去掉_
    [arrayM addObject:key];
}
free(ivars);
objc_setAssociatedObject(self, propertiesKey, arrayM, OBJC_ASSOCIATION_COPY_NONATOMIC);
NSLog(@"%@", arrayM); 输出是
(
    age,
    height,
    name
)objc_setAssociatedObject
方法的参数解释: 第一个参数id object, 当前对象 第二个参数const void *key, 关联的key，是c字符串 第三个参数id value, 被关联的对象 第四个参数objc_AssociationPolicy policy关联引用的规则，取值有以下几种：
enum {
    OBJC_ASSOCIATION_ASSIGN = 0,
    OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1,
    OBJC_ASSOCIATION_COPY_NONATOMIC = 3,
    OBJC_ASSOCIATION_RETAIN = 01401,
    OBJC_ASSOCIATION_COPY = 01403
}; 
如果想要获取已经关联的对象，通过key取得即可
NSArray *pList = objc_getAssociatedObject(Person, propertiesKey); 可以将以上两种操作封装起来,为Person类增加一个properties类方法,封装上面的操作，用于方便获取类的属性列表。
const char* propertiesKey = "propertiesKey";

@implementation Person
+ (NSArray *)properties {

    NSArray *pList = objc_getAssociatedObject(self, propertiesKey);
    if (pList != nil) {
        return pList;
    }

    unsigned int count = 0;
    Ivar *ivars = class_copyIvarList([self class], &count);

    NSMutableArray *arrayM = [NSMutableArray arrayWithCapacity:count];

    for (unsigned int i = 0; i < count; ++i) {
        Ivar pty = ivars[i];
        const char *cname = ivar_getName(ivars[i]);
        NSString *name = [NSString stringWithUTF8String:cname];
        NSString *key = [name substringFromIndex:1];
        [arrayM addObject:key];
    }
    free(ivars);
    objc_setAssociatedObject(self, propertiesKey, arrayM,                          OBJC_ASSOCIATION_COPY_NONATOMIC);
    return arrayM.copy;
}
@end            

void abc(id self, SEL _cmd){
    NSLog(@"%@说了hello", [self name]);
}

@implementation Person

//动态添加方法：在resolve中添加相应的方法，注意是类方法还是对象方法。
+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    if ([NSStringFromSelector(sel) isEqualToString:@"sayHi"]) {
        class_addMethod(self, sel, abc, "v@:"); // 为sel指定实现为abc
    }
    return YES;
}
@end    

Person *p = [[Person alloc] init];

p.name = @"zhangsan";
p.age = 10;
[p performSelector:@selector(sayHi:) withObject:@"world"]; // 增加了一个参数，多了冒号 对Person类中的代码做了修改
void abc(id self, SEL _cmd, NSString *content){ // 增加了一个参数content
    NSLog(@"%@说了hello%@", [self name], content);
}

@implementation Person

//动态添加方法：在resolve中添加相应的方法，注意是类方法还是对象方法。
+ (BOOL)resolveInstanceMethod:(SEL)sel
{
    if ([NSStringFromSelector(sel) isEqualToString:@"sayHi:"]) {
        class_addMethod(self, sel, abc, "v@:@"); // 增加了一个对象类型参数 增加了@
    }
    return YES;
}
@end 
输出为:
zhangsan说了helloworld    

#import "ViewController.h"
#import <objc/runtime.h>
#import <objc/message.h>
#import "Person.h"

static void printSchool(id self, SEL _cmd) {
    NSLog(@"我的学校是%@", [self valueForKey:@"schoolName"]);
}

@implementation ViewController

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    Class classStudent = objc_allocateClassPair(Person.class, "Student", 0);

    // 添加一个NSString的变量，第四个参数是对其方式，第五个参数是参数类型
    if (class_addIvar(classStudent, "schoolName", sizeof(NSString *), 0, "@")) {
        NSLog(@"添加成员变量schoolName成功");
    }

    // 为Student类添加方法 "v@:"这种写法见参数类型连接
    if (class_addMethod(classStudent, @selector(printSchool), (IMP)printSchool,     "v@:")) {
        NSLog(@"添加方法printSchool:成功");
    }

    // 注册这个类到runtime系统中就可以使用他了
    objc_registerClassPair(classStudent); // 返回void



    // 使用创建的类
    id student = [[classStudent alloc] init];
    NSString *schoolName = @"清华大学";
    // 给刚刚添加的变量赋值
    // object_setInstanceVariable(student, "schoolName", (void *)&str);在ARC下不允许使用
    [student setValue:schoolName forKey:@"schoolName"];
    // 调用printSchool方法，也就是给student这个接受者发送printSchool:这个消息
    // objc_msgSend(student, "printSchool"); // 我尝试用这种方法调用但是没有成功
    [student performSelector:@selector(printSchool) withObject:nil]; // 动态调用未显式在类中声明的方法

}
@end 输出的结果是:
添加成员变量schoolName成功
添加方法printSchool成功
我的学校是清华大学