序言
本篇文章主要介绍runtime有关API及使用
一 类
1.1 动态创建一个类(参数:父类,类名,额外的内存空间)
Class objc_allocateClassPair(Class superclass, const char *name, size_t extraBytes)
1.2 注册一个类(要在类注册之前添加成员变量)
void objc_registerClassPair(Class cls)
1.3 销毁一个类
void objc_disposeClassPair(Class cls)
- 以上三个方法使用下面例子做讲解
// 建一个命令行工程
#import <Foundation/Foundation.h>
#import <objc/runtime.h>
void run(id self, SEL _cmd) {
NSLog(@"_____ %@ - %@", self, NSStringFromSelector(_cmd));
}
int main(int argc, const char * argv[]) {
@autoreleasepool {
// insert code here...
// 动态创建一个类
Class newClass = objc_allocateClassPair([NSObject class], "CSDog", 0);
// 添加属性
class_addIvar(newClass, "_age", 4, 1, @encode(int));
class_addIvar(newClass, "_weight", 4, 1, @encode(int));
// 添加方法
class_addMethod(newClass, @selector(run), (IMP)run, "v@:");
// 注册类
objc_registerClassPair(newClass);
id dog = [[newClass alloc] init];
[dog setValue:@10 forKey:@"_age"];
[dog setValue:@20 forKey:@"_weight"];
[dog run];
NSLog(@"%@ %@", [dog valueForKey:@"_age"], [dog valueForKey:@"_weight"]);
// 在不需要这个类时释放
objc_disposeClassPair(newClass);
}
return 0;
}
运行结果
1.4 获取isa指向的Class
Class object_getClass(id obj)
1.5 设置isa指向的Class
Class object_setClass(id obj, Class cls)
1.6 判断一个OC对象是否为Class
BOOL object_isClass(id obj)
- 上面三个方法以下面代码做例子
@interface CSPersion : NSObject
- (void)run;
@end
@implementation CSPersion
- (void)run {
NSLog(@"%s", __func__);
}
@end
@interface CSCar : NSObject
- (void)run;
@end
@implementation CSCar
- (void)run {
NSLog(@"%s", __func__);
}
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
// insert code here...
CSPersion *persion = [[CSPersion alloc] init];
[persion run];
object_setClass(persion, [CSCar class]);
[persion run];
object_getClass([CSPersion class]);
NSLog(@"%p %p", object_getClass([CSPersion class]), [CSPersion class]);
NSLog(@"%d %d %d",
object_isClass(persion),
object_isClass([CSPersion class]),
object_isClass(object_getClass([CSPersion class]))
);
}
return 0;
}
运行结果如下
1.7 判断一个Class是否为元类
BOOL class_isMetaClass(Class cls)
1.8 获取父类
Class class_getSuperclass(Class cls)
二 成员变量
公共使用类
@interface CSPersion : NSObject
@property (assign, nonatomic) int ID;
@property (assign, nonatomic) int weight;
@property (assign, nonatomic) int age;
@property (copy, nonatomic) NSString *name;
- (void)run;
@end
2.1 获取一个实例变量信息
Ivar class_getInstanceVariable(Class cls, const char *name)
2.2 获取成员变量的相关信息
const char *ivar_getName(Ivar v)
const char *ivar_getTypeEncoding(Ivar v)
2.1,2.2使用如下代码做例子
int main(int argc, const char * argv[]) {
@autoreleasepool {
// insert code here...
// 1.获取成员变量信息
Ivar ageIvar = class_getInstanceVariable([CSPersion class], "_age");
NSLog(@"%s %s",ivar_getName(ageIvar),ivar_getTypeEncoding(ageIvar));
}
return 0;
}
运行结果
2.3 设置和获取成员变量的值
void object_setIvar(id obj, Ivar ivar, id value)
id object_getIvar(id obj, Ivar ivar)
代码例子如下
int main(int argc, const char * argv[]) {
@autoreleasepool {
// 2. 设置和获取成员变量的值
CSPersion *persion = [[CSPersion alloc] init];
Ivar nameIvar = class_getInstanceVariable([CSPersion class], "_name");
Ivar ageIvar = class_getInstanceVariable([CSPersion class], "_age");
object_setIvar(persion, nameIvar, @"123");
object_setIvar(persion, ageIvar, (__bridge id)(void *)10);
NSLog(@"%@ %d", persion.name, persion.age);
}
return 0;
}
运行结果如下
2.4 动态添加成员变量(已经注册的类是不能动态添加成员变量的)
BOOL class_addIvar(Class cls, const char * name, size_t size, uint8_t alignment, const char * types)
int main(int argc, const char * argv[]) {
@autoreleasepool {
// 动态创建一个类
Class newClass = objc_allocateClassPair([NSObject class], "CSDog", 0);
// 添加属性
class_addIvar(newClass, "_age", 4, 1, @encode(int));
class_addIvar(newClass, "_weight", 4, 1, @encode(int));
// 添加方法
class_addMethod(newClass, @selector(run), (IMP)run, "v@:");
// 注册类
objc_registerClassPair(newClass);
id dog = [[newClass alloc] init];
[dog setValue:@10 forKey:@"_age"];
[dog setValue:@20 forKey:@"_weight"];
[dog run];
NSLog(@"%@ %@", [dog valueForKey:@"_age"], [dog valueForKey:@"_weight"]);
// 在不需要这个类时释放
objc_disposeClassPair(newClass);
}
return 0;
}
运行结果如下
2.5 拷贝实例变量列表(最后需要调用free释放)
Ivar *class_copyIvarList(Class cls, unsigned int *outCount)
int main(int argc, const char * argv[]) {
@autoreleasepool {
// 4.成员变量的数量
unsigned int count;
Ivar *ivars = class_copyIvarList([CSPersion class], &count);
for (int i = 0; i < count; i++) {
// 取出i位置的成员变量
Ivar ivar = ivars[i];
NSLog(@"%s %s", ivar_getName(ivar), ivar_getTypeEncoding(ivar));
}
free(ivars);
}
return 0;
}
运行结果如下
三 属性
3.1 获取一个属性
objc_property_t class_getProperty(Class cls, const char *name)
3.2 拷贝属性列表(最后需要调用free释放)
objc_property_t *class_copyPropertyList(Class cls, unsigned int *outCount)
3.3 动态添加属性
BOOL class_addProperty(Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount)
3.4 动态替换属性
void class_replaceProperty(Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount)
3.5 获取属性的一些信息
const char *property_getName(objc_property_t property)
const char *property_getAttributes(objc_property_t property)
四 方法
4.1 获得一个实例方法、类方法
Method class_getInstanceMethod(Class cls, SEL name)
Method class_getClassMethod(Class cls, SEL name)
4.2 方法实现相关操作
IMP class_getMethodImplementation(Class cls, SEL name)
IMP method_setImplementation(Method m, IMP imp)
void method_exchangeImplementations(Method m1, Method m2)
4.3 拷贝方法列表(最后需要调用free释放)
Method *class_copyMethodList(Class cls, unsigned int *outCount)
4.4 动态添加方法
BOOL class_addMethod(Class cls, SEL name, IMP imp, const char *types)
4.5 动态替换方法
IMP class_replaceMethod(Class cls, SEL name, IMP imp, const char *types)
4.6 获取方法的相关信息(带有copy的需要调用free去释放)
SEL method_getName(Method m)
IMP method_getImplementation(Method m)
const char *method_getTypeEncoding(Method m)
unsigned int method_getNumberOfArguments(Method m)
char *method_copyReturnType(Method m)
char *method_copyArgumentType(Method m, unsigned int index)
4.7 选择器相关
const char *sel_getName(SEL sel)
SEL sel_registerName(const char *str)
4.8 用block作为方法实现
IMP imp_implementationWithBlock(id block)
id imp_getBlock(IMP anImp)
BOOL imp_removeBlock(IMP anImp)
五 实践
5.1 交换方法实现 method_exchangeImplementations
如果需要监听所有按钮的点击事件
NS_CLASS_AVAILABLE_IOS(2_0) @interface UIButton : UIControl <NSCoding>
- (void)addTarget:(nullable id)target action:(SEL)action forControlEvents:(UIControlEvents)controlEvents;
- (void)sendAction:(SEL)action to:(nullable id)target forEvent:(nullable UIEvent *)event;
UIButton
继承自UIControl
,并且添加点击事件方法addTarget:action:forControlEvents
最终是调用sendAction:to:forEvent
方法,所以交换该方法即可。
1.定义UIControl的类扩展
#import "UIControl+Extension.h"
#import <objc/runtime.h>
@implementation UIControl (Extension)
+ (void)load {
// hork:钩子函数
Method method1 = class_getInstanceMethod(self, @selector(sendAction:to:forEvent:));
Method method2 = class_getInstanceMethod(self, @selector(cs_sendAction:to:forEvent:));
method_exchangeImplementations(method1, method2);
}
- (void)cs_sendAction:(SEL)action to:(id)target forEvent:(UIEvent *)event {
NSLog(@"%@-%@-%@", self, target, NSStringFromSelector(action));
// 调用系统原理的实现
[self cs_sendAction:action to:target forEvent:event];
if ([self isKindOfClass:[UIButton class]]) {
NSLog(@"拦截了所有按钮的事件");
}
}
@end
运行结果
5.2 防止数组插入空值
我们知道如果直接给数组插入空值会崩溃
NSString *obj = nil;
NSMutableArray *array = [NSMutableArray array];
[array addObject:@"jack"];
[array insertObject:obj atIndex:0];
NSLog(@"%@", array);
运行结果
如何可以避免类似崩溃发生?
交换数组方法的实现
#import "NSMutableArray+Extension.h"
#import <objc/runtime.h>
@implementation NSMutableArray (Extension)
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
// 类簇:NSString、NSArray、NSDictionary,真实类型是其他类型
Class cls = NSClassFromString(@"__NSArrayM");
Method method1 = class_getInstanceMethod(cls, @selector(insertObject:atIndex:));
Method method2 = class_getInstanceMethod(cls, @selector(cs_insertObject:atIndex:));
method_exchangeImplementations(method1, method2);
});
}
- (void)cs_insertObject:(id)anObject atIndex:(NSUInteger)index {
if (anObject == nil) {
return;
}
[self cs_insertObject:anObject atIndex:index];
}
@end
运行结果
结果正常运行,不会发生崩溃
5.3 防止字典中key为空
1.如果往一个可变字典中插入一个键值对,并且key为空,则会发生崩溃
NSString *obj = nil;
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
dict[@"name"] = @"jack";
dict[obj] = @"rose";
dict[@"age"] = obj;
NSLog(@"%@", dict);
运行结果
如果避免类似事情发生?
给NSMutableDictionary
添加类扩展,并交换方法实现
#import "NSMutableDictionary+Extension.h"
#import <objc/runtime.h>
@implementation NSMutableDictionary (Extension)
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
Class cls = NSClassFromString(@"__NSDictionaryM");
Method method1 = class_getInstanceMethod(cls, @selector(setObject:forKeyedSubscript:));
Method method2 = class_getInstanceMethod(cls, @selector(cs_setObject:forKeyedSubscript:));
method_exchangeImplementations(method1, method2);
Class cls2 = NSClassFromString(@"__NSDictionaryI");
Method method3 = class_getInstanceMethod(cls2, @selector(objectForKeyedSubscript:));
Method method4 = class_getInstanceMethod(cls2, @selector(cs_objectForKeyedSubscript:));
method_exchangeImplementations(method3, method4);
});
}
- (void)cs_setObject:(id)obj forKeyedSubscript:(id<NSCopying>)key {
if (!key) {
return;
}
[self cs_setObject:obj forKeyedSubscript:key];
}
- (id)cs_objectForKeyedSubscript:(id)key {
if (!key) {
return nil;
}
return [self cs_objectForKeyedSubscript:key];
}
@end
运行结果
正常运行,不会发生崩溃
本文主要参考MJ老师的课件,非常感谢MJ老师,并且自己附带相应的例子。
项目连接地址-runtime_API
项目连接地址-runtime_exchangeMethod
更多有关runtime文章请看下面
iOS - runtime -详解
iOS Runtime原理及使用
iOS - runtime如何通过selector找到对应的 IMP地址(分别考虑类方法和实例方法)
iOS - Runtime之面试题详解一
iOS-runtime之面试题详解二
iOS runtime的使用场景-实战篇