今天，讲这个系列的第四篇，是关于Protocol。
5.Protocol
首先，我们依然寻找最简单的方法：
const char * _Nonnull
protocol_getName(Protocol * _Nonnull proto)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码这个方法是获得协议的名称。后面我们打印协议就通过这个函数。 既然可以通过协议来获取名称，那么也可以通过名称来获取协议，就是下面这个方法：
Protocol * _Nullable
objc_getProtocol(const char * _Nonnull name)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码我们新建一个协议类PlayProtocol:
-(void)protocolCommen {
Protocol *protocol = objc_getProtocol("PlayProtocol");
if (protocol) {
const char* name = protocol_getName(protocol);
NSLog(@"name = %s",name);
}else {
NSLog(@"不存在该协议");
}
}
复制代码运行结果：
不存在该协议
复制代码奇了怪了，明明新建了，为什么找不到了，是不是因为没有使用呢？ 我们随便找个类去遵循这个协议，就拿我们前几篇新建的那个Person类吧。 再运行一次：
name = PlayProtocol
复制代码这次没错了，最后的结论是，必须**register**（只要有Class遵循这个Protocol，就算register）的Protocol才能通过objc_getProtocol找到。 下面这个方法是判断a协议是否遵循b协议：
BOOL
protocol_conformsToProtocol(Protocol * _Nullable proto,
Protocol * _Nullable other)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码我们新建一个SingProtocol协议，让PlayProtocol遵循SingProtocol协议，即
@protocol PlayProtocol <SingProtocol>
@end
复制代码我们来实践一下吧：
-(void)conformsToProtocol {
Protocol* playProtocol = objc_getProtocol("PlayProtocol");
Protocol* singProtocol = objc_getProtocol("SingProtocol");
BOOL isConform = protocol_conformsToProtocol(playProtocol, singProtocol);
NSLog(@"PlayProtocol协议 %@ SingProtocol协议",isConform?@"遵循":@"不遵循");
BOOL isConform2 = protocol_conformsToProtocol(singProtocol, playProtocol);
NSLog(@"SingProtocol协议 %@ PlayProtocol协议",isConform2?@"遵循":@"不遵循");
}
复制代码运行结果：
2019-02-28 09:41:30.362087+0800 Runtime-Demo[86769:5791422] PlayProtocol协议 遵循 SingProtocol协议
2019-02-28 09:41:30.362134+0800 Runtime-Demo[86769:5791422] SingProtocol协议 不遵循 PlayProtocol协议
复制代码我们可以PlayProtocol协议遵循了SingProtocol协议。 下面这个方法是指判断2个协议是否相等。
BOOL
protocol_isEqual(Protocol * _Nullable proto, Protocol * _Nullable other)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码我们新建一个RunProtocol协议也遵循SingProtocol。因为我们之前PlayProtocol协议也遵循了SingProtocol协议，并且这两个协议都没有各自的方法。那我们来测试下：
-(void)isEqual {
Protocol* playProtocol = objc_getProtocol("PlayProtocol");
Protocol* runProtocol = objc_getProtocol("SingProtocol");
BOOL isEqual = protocol_isEqual(playProtocol, runProtocol);
NSLog(@"%@",isEqual?@"相等":@"不相等");
}
复制代码运行之后：
不相等
复制代码又一次出乎意料，难道真的只有完全相等才行吗？看下源码吧：
BOOL protocol_isEqual(Protocol *self, Protocol *other)
{
if (self == other) return YES;
if (!self || !other) return NO;
if (!protocol_conformsToProtocol(self, other)) return NO;
if (!protocol_conformsToProtocol(other, self)) return NO;
return YES;
}
复制代码真的是只有完全相等才能返回YES： 那么我们改下代码：
-(void)isEqual2 {
Protocol* playProtocol1 = objc_getProtocol("PlayProtocol");
NSLog(@"playProtocol1 = %@",playProtocol1);
Protocol* playProtocol2 = objc_getProtocol("PlayProtocol");
NSLog(@"playProtocol2 = %@",playProtocol2);
BOOL isEqual = protocol_isEqual(playProtocol1, playProtocol2);
NSLog(@"%@",isEqual?@"相等":@"不相等");
}
复制代码运行结果：
2019-02-28 10:18:07.799200+0800 Runtime-Demo[87377:5813138] playProtocol1 = <Protocol: 0x10463e9a0>
2019-02-28 10:18:07.799250+0800 Runtime-Demo[87377:5813138] playProtocol2 = <Protocol: 0x10463e9a0>
2019-02-28 10:18:07.799301+0800 Runtime-Demo[87377:5813138] 相等
复制代码只有当两个协议对象完全相同（内存地址一样），才能返回YES。
下面两个方法也是和Method有关。
struct objc_method_description
protocol_getMethodDescription(Protocol * _Nonnull proto, SEL _Nonnull aSel,
BOOL isRequiredMethod, BOOL isInstanceMethod)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
struct objc_method_description * _Nullable
protocol_copyMethodDescriptionList(Protocol * _Nonnull proto,
BOOL isRequiredMethod,
BOOL isInstanceMethod,
unsigned int * _Nullable outCount)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码protocol_getMethodDescription找到某个协议的某个方法，protocol_copyMethodDescriptionList找到某个协议的所有方法。我们在SingProtocol协议里面加几个方法：
@protocol SingProtocol <NSObject>
@required
-(void)singFolkSongs;
+(void)singRockSongs;
@optional
-(void)singPopularSongs;
+(void)singMetalSongs;
@end
复制代码我们先实践下protocol_getMethodDescription，protocol_getMethodDescription有4个参数，proto指定的协议，aSel指定的方法，isRequiredMethod是否是必要方法，isInstanceMethod是否是实例方法：
-(void)getMethodDescription {
Protocol* singProtocol = objc_getProtocol("SingProtocol");
struct objc_method_description method = protocol_getMethodDescription(singProtocol, sel_registerName("singFolkSongs"), YES, YES);
NSLog(@"singFolkSongs方法 name = %s,types = %s", sel_getName(method.name) ,method.types);
struct objc_method_description method1 = protocol_getMethodDescription(singProtocol, sel_registerName("singRockSongs"), YES, NO);
NSLog(@"singRockSongs方法 name = %s,types = %s", sel_getName(method1.name) ,method1.types);
struct objc_method_description method2 = protocol_getMethodDescription(singProtocol, sel_registerName("singPopularSongs"), NO, YES);
NSLog(@"singPopularSongs方法 name = %s,types = %s", sel_getName(method2.name) ,method2.types);
struct objc_method_description method3 = protocol_getMethodDescription(singProtocol, sel_registerName("singMetalSongs"), NO, NO);
NSLog(@"singMetalSongs方法 name = %s,types = %s", sel_getName(method3.name) ,method3.types);
}
复制代码运行结果：
2019-02-28 10:37:32.929473+0800 Runtime-Demo[87693:5820462] singFolkSongs方法 name = singFolkSongs,types = v16@0:8
2019-02-28 10:37:32.929514+0800 Runtime-Demo[87693:5820462] singRockSongs方法 name = singRockSongs,types = v16@0:8
2019-02-28 10:37:32.929528+0800 Runtime-Demo[87693:5820462] singPopularSongs方法 name = singPopularSongs,types = v16@0:8
2019-02-28 10:37:32.929540+0800 Runtime-Demo[87693:5820462] singMetalSongs方法 name = singMetalSongs,types = v16@0:8
复制代码运行结果没毛病！！！ 我们再看下protocol_copyMethodDescriptionList这个函数，是用来找某个协议符合条件的方法列表，参数含义和protocol_getMethodDescription类似，那么我就直接试炼了：
-(void)copyMethodDescriptionList {
Protocol* singProtocol = objc_getProtocol("SingProtocol");
unsigned int count1;
struct objc_method_description *methodList1 = protocol_copyMethodDescriptionList(singProtocol, YES, YES, &count1);
NSLog(@"-----必要方法以及实例方法-----");
for (unsigned int i = 0; i < count1; i++) {
struct objc_method_description method = methodList1[i];
NSLog(@"name = %s,types = %s", sel_getName(method.name) ,method.types);
}
free(methodList1);
unsigned int count2;
struct objc_method_description *methodList2 = protocol_copyMethodDescriptionList(singProtocol, YES, NO, &count2);
NSLog(@"-----必要方法以及类方法-----");
for (unsigned int i = 0; i < count2; i++) {
struct objc_method_description method = methodList2[i];
NSLog(@"name = %s,types = %s", sel_getName(method.name) ,method.types);
}
free(methodList2);
unsigned int count3;
struct objc_method_description *methodList3 = protocol_copyMethodDescriptionList(singProtocol, NO, NO, &count3);
NSLog(@"-----可选方法以及类方法-----");
for (unsigned int i = 0; i < count3; i++) {
struct objc_method_description method = methodList3[i];
NSLog(@"name = %s,types = %s", sel_getName(method.name) ,method.types);
}
free(methodList3);
unsigned int count4;
struct objc_method_description *methodList4 = protocol_copyMethodDescriptionList(singProtocol, NO, YES, &count4);
NSLog(@"-----可选方法以及实例方法-----");
for (unsigned int i = 0; i < count4; i++) {
struct objc_method_description method = methodList4[i];
NSLog(@"name = %s,types = %s", sel_getName(method.name) ,method.types);
}
free(methodList4);
}
复制代码运行结果：
2019-02-28 10:46:29.075801+0800 Runtime-Demo[87839:5823598] -----必要方法以及实例方法-----
2019-02-28 10:46:29.075836+0800 Runtime-Demo[87839:5823598] name = singFolkSongs,types = v16@0:8
2019-02-28 10:46:29.075849+0800 Runtime-Demo[87839:5823598] -----必要方法以及类方法-----
2019-02-28 10:46:29.075857+0800 Runtime-Demo[87839:5823598] name = singRockSongs,types = v16@0:8
2019-02-28 10:46:29.075866+0800 Runtime-Demo[87839:5823598] -----可选方法以及类方法-----
2019-02-28 10:46:29.075873+0800 Runtime-Demo[87839:5823598] name = singMetalSongs,types = v16@0:8
2019-02-28 10:46:29.075882+0800 Runtime-Demo[87839:5823598] -----可选方法以及实例方法-----
2019-02-28 10:46:29.075889+0800 Runtime-Demo[87839:5823598] name = singPopularSongs,types = v16@0:8
复制代码和我们分析的一样。 既然可以从协议里获得方法，那么也可以获得协议里的属性：
objc_property_t _Nullable
protocol_getProperty(Protocol * _Nonnull proto,
const char * _Nonnull name,
BOOL isRequiredProperty, BOOL isInstanceProperty)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
objc_property_t _Nonnull * _Nullable
protocol_copyPropertyList(Protocol * _Nonnull proto,
unsigned int * _Nullable outCount)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
objc_property_t _Nonnull * _Nullable
protocol_copyPropertyList2(Protocol * _Nonnull proto,
unsigned int * _Nullable outCount,
BOOL isRequiredProperty, BOOL isInstanceProperty)
OBJC_AVAILABLE(10.12, 10.0, 10.0, 3.0, 2.0);
复制代码protocol_getProperty是获取协议里的属性，protocol_copyPropertyList和protocol_copyPropertyList2都是获取协议里的属性列表。protocol_copyPropertyList2是更加细分条件的去获取协议里的属性列表。 我们在SingProtocol里添加若干属性，如下：
@protocol SingProtocol <NSObject>
@required
-(void)singFolkSongs;
+(void)singRockSongs;
@property(nonatomic,copy)NSString* folkSongs;
@property(nonatomic,copy,class)NSString* rockSongs;
@optional
-(void)singPopularSongs;
+(void)singMetalSongs;
@property(nonatomic,copy)NSString* popularSongs;
@property(nonatomic,copy,class)NSString* metalSongs;
@end
复制代码在上面我们看到了陌生的class关键词，iOS8之后，LLVM已经支持显式声明类属性了，这是为了与Swift中的类属性互操作而引入的，大家可以找下相关文档。 另外在协议的属性里面，是不分@optional和@required，我们在源码里可以看到：
static property_t *
protocol_getProperty_nolock(protocol_t *proto, const char *name,
bool isRequiredProperty, bool isInstanceProperty)
{
runtimeLock.assertLocked();
if (!isRequiredProperty) {
// Only required properties are currently supported.
return nil;
}
property_list_t *plist = isInstanceProperty ?
proto->instanceProperties : proto->classProperties();
if (plist) {
for (auto& prop : *plist) {
if (0 == strcmp(name, prop.name)) {
return ∝
}
}
}
if (proto->protocols) {
uintptr_t i;
for (i = 0; i < proto->protocols->count; i++) {
protocol_t *p = remapProtocol(proto->protocols->list[i]);
property_t *prop =
protocol_getProperty_nolock(p, name,
isRequiredProperty,
isInstanceProperty);
if (prop) return prop;
}
}
return nil;
}
复制代码protocol_getProperty的底层就是调用的这个方法，我们可以看到里面：
if (!isRequiredProperty) {
// Only required properties are currently supported.
return nil;
}
复制代码这里明确说明了目前只支持required的属性，一旦传入isRequiredProperty为NO的话，直接返回nil。 知道了这些概念，我们实践下：
-(void)getProperty_Protocol {
Protocol* singProtocol = objc_getProtocol("SingProtocol");
objc_property_t rockSongsProperty = protocol_getProperty(singProtocol, "rockSongs", YES, NO);
const char* rockSongsName = property_getName(rockSongsProperty);
NSLog(@"rockSongs 属性 name = %s",rockSongsName);
objc_property_t folkSongsProperty = protocol_getProperty(singProtocol, "folkSongs", YES, YES);
const char* folkSongsName = property_getName(folkSongsProperty);
NSLog(@"folkSongs 属性 name = %s",folkSongsName);
objc_property_t popularSongsProperty = protocol_getProperty(singProtocol, "popularSongs", YES, YES);
const char* popularSongsName = property_getName(popularSongsProperty);
NSLog(@"popularSongs 属性 name = %s",popularSongsName);
objc_property_t metalSongsProperty = protocol_getProperty(singProtocol, "metalSongs", YES, NO);
const char* metalSongsName = property_getName(metalSongsProperty);
NSLog(@"metalSongs 属性 name = %s",metalSongsName);
}
复制代码打印结果：
2019-02-28 11:49:17.619145+0800 Runtime-Demo[88910:5849614] rockSongs 属性 name = rockSongs
2019-02-28 11:49:17.619184+0800 Runtime-Demo[88910:5849614] folkSongs 属性 name = folkSongs
2019-02-28 11:49:17.619196+0800 Runtime-Demo[88910:5849614] popularSongs 属性 name = popularSongs
2019-02-28 11:49:17.619207+0800 Runtime-Demo[88910:5849614] metalSongs 属性 name = metalSongs
复制代码没毛病！！！ 同样，我们实践下protocol_copyPropertyList和protocol_copyPropertyList2方法：
-(void)copyPropertyList_protocol {
Protocol* singProtocol = objc_getProtocol("SingProtocol");
NSLog(@"-----copyPropertyList------");
unsigned int count;
objc_property_t* propertyList = protocol_copyPropertyList(singProtocol, &count);
for (unsigned int i = 0; i < count; i++) {
objc_property_t property = propertyList[i];
NSLog(@"name = %s",property_getName(property));
}
free(propertyList);
NSLog(@"-----copyPropertyList2---instance propertys---");
unsigned int count2;
objc_property_t* propertyList2 = protocol_copyPropertyList2(singProtocol, &count2, YES, YES);
for (unsigned int i = 0; i < count2; i++) {
objc_property_t property = propertyList2[i];
NSLog(@"name = %s",property_getName(property));
}
free(propertyList2);
NSLog(@"-----copyPropertyList2---class propertys---");
unsigned int count3;
objc_property_t* propertyList3 = protocol_copyPropertyList2(singProtocol, &count3, YES, NO);
for (unsigned int i = 0; i < count3; i++) {
objc_property_t property = propertyList3[i];
NSLog(@"name = %s",property_getName(property));
}
free(propertyList3);
}
复制代码运行结果：
2019-02-28 13:30:34.259328+0800 Runtime-Demo[90302:5888309] -----copyPropertyList------
2019-02-28 13:30:34.259367+0800 Runtime-Demo[90302:5888309] name = folkSongs
2019-02-28 13:30:34.259378+0800 Runtime-Demo[90302:5888309] name = popularSongs
2019-02-28 13:30:34.259387+0800 Runtime-Demo[90302:5888309] -----copyPropertyList2---instance propertys---
2019-02-28 13:30:34.259395+0800 Runtime-Demo[90302:5888309] name = folkSongs
2019-02-28 13:30:34.259403+0800 Runtime-Demo[90302:5888309] name = popularSongs
2019-02-28 13:30:34.259411+0800 Runtime-Demo[90302:5888309] -----copyPropertyList2---class propertys---
2019-02-28 13:30:34.259418+0800 Runtime-Demo[90302:5888309] name = rockSongs
2019-02-28 13:30:34.259426+0800 Runtime-Demo[90302:5888309] name = metalSongs
复制代码根据打印结果protocol_copyPropertyList方法只能获得实例属性的属性列表。protocol_copyPropertyList2方法根据你传的isInstanceProperty的不同而返回不同的属性列表（实例属性列表或者类属性列表）。 那么，如何查看一个类是否遵循某个协议呢，当然是下面这个方法：
BOOL
class_conformsToProtocol(Class _Nullable cls, Protocol * _Nullable protocol)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码我们已知Person类已经遵循了PlayProtocol，那么测试下：
-(void)conformsToProtocol_class {
Protocol* playProtocol = objc_getProtocol("PlayProtocol");
Protocol* runProtocol = objc_getProtocol("RunProtocol");
BOOL isConforms = class_conformsToProtocol(objc_getClass("Person"), playProtocol);
BOOL isConforms2 = class_conformsToProtocol(objc_getClass("Person"), runProtocol);
NSLog(@"Person %@ PlayProtocol协议",isConforms?@"遵循":@"不遵循");
NSLog(@"Person %@ RunProtocol协议",isConforms2?@"遵循":@"不遵循");
}
复制代码运行结果：
2019-02-28 13:57:46.292107+0800 Runtime-Demo[90742:5897636] Person 遵循 PlayProtocol协议
2019-02-28 13:57:46.292143+0800 Runtime-Demo[90742:5897636] Person 不遵循 RunProtocol协议
复制代码完全正确！！！
Protocol * __unsafe_unretained _Nonnull * _Nullable
protocol_copyProtocolList(Protocol * _Nonnull proto,
unsigned int * _Nullable outCount)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码这个方法是获得一个协议所遵循的协议的列表。新建一个新协议EatProtocol，遵循RunProtocol,SingProtocol,PlayProtocol，并让Person类遵循EatProtocol（目的是能获得这个协议）如下：
@protocol EatProtocol <RunProtocol,SingProtocol,PlayProtocol>
@end
复制代码准备工作好了，那么久开始了：
-(void)copyProtocolList {
Protocol* eatProtocol = objc_getProtocol("EatProtocol");
unsigned int count;
__unsafe_unretained Protocol** protocolList = protocol_copyProtocolList(eatProtocol, &count);
for (unsigned int i = 0; i < count ; i++) {
Protocol* protocol = protocolList[i];
NSLog(@"%s",protocol_getName(protocol));
}
free(protocolList);
}
复制代码运行结果：
2019-02-28 14:17:35.718944+0800 Runtime-Demo[91079:5905870] RunProtocol
2019-02-28 14:17:35.718983+0800 Runtime-Demo[91079:5905870] SingProtocol
2019-02-28 14:17:35.718992+0800 Runtime-Demo[91079:5905870] PlayProtocol
复制代码事实上也遵循了这三个协议。 下面这个方法是获得某个类所遵循的协议数组
Protocol * __unsafe_unretained _Nonnull * _Nullable
class_copyProtocolList(Class _Nullable cls, unsigned int * _Nullable outCount)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码我们在Person类里遵循了PlayProtocol,EatProtocol两个协议：
-(void)copyProtocolList_class {
Class class = objc_getClass("Person");
unsigned int count;
__unsafe_unretained Protocol** protocolList = class_copyProtocolList(class, &count);
for (unsigned int i = 0; i < count ; i++) {
Protocol* protocol = protocolList[i];
NSLog(@"%s",protocol_getName(protocol));
}
free(protocolList);
}
复制代码运行结果：
2019-02-28 14:26:38.842578+0800 Runtime-Demo[91226:5908955] PlayProtocol
2019-02-28 14:26:38.842616+0800 Runtime-Demo[91226:5908955] EatProtocol
复制代码Person类事实遵循了PlayProtocol,EatProtocol两个协议。 下面这个函数是获得整个工程里面所遵循的协议：
Protocol * __unsafe_unretained _Nonnull * _Nullable
objc_copyProtocolList(unsigned int * _Nullable outCount)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码运行结果：
2019-02-28 14:30:14.378254+0800 Runtime-Demo[91287:5910354] SCNAnimation
2019-02-28 14:30:14.378305+0800 Runtime-Demo[91287:5910354] GEOBatchOpportunisticTileDownloaderDelegate
2019-02-28 14:30:14.378321+0800 Runtime-Demo[91287:5910354] PTSettingsKeyObserver
2019-02-28 14:30:14.378339+0800 Runtime-Demo[91287:5910354] _SFPBUserReportRequest
2019-02-28 14:30:14.378354+0800 Runtime-Demo[91287:5910354] _UIAlertControllerTextFieldViewControllerContaining
2019-02-28 14:30:14.378370+0800 Runtime-Demo[91287:5910354] SFVerticalLayoutCardSection
2019-02-28 14:30:14.378386+0800 Runtime-Demo[91287:5910354] MKInfoCardThemeListener
......
......
复制代码我们会发现，打印了很多协议，其中大多数都是系统自带的协议，也有我们自定义的协议。 和Class一样还能动态的生成Protocol。
Protocol * _Nullable
objc_allocateProtocol(const char * _Nonnull name)
OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0, 2.0);
void
objc_registerProtocol(Protocol * _Nonnull proto)
OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0, 2.0);
复制代码这两个函数和objc_allocateClassPair和objc_registerClassPair一样，必须register才能使用。
-(void)allocateProtocol {
Protocol* protocol = objc_allocateProtocol("TestProtocol");
objc_registerProtocol(protocol);
NSLog(@"%s",protocol_getName(protocol));
}
复制代码运行结果：
TestProtocol
复制代码下面几个方法是给协议添加内容的。
void
protocol_addMethodDescription(Protocol * _Nonnull proto, SEL _Nonnull name,
const char * _Nullable types,
BOOL isRequiredMethod, BOOL isInstanceMethod)
OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0, 2.0);
复制代码这个方法是给协议添加Method的。给协议添加方法有两种情况，第一，是给已经创建好并且已经register的协议添加方法，第二，是给动态生成的协议添加方法。 第一种情况：
-(void)addMethodDescription1 {
Protocol* eatProtocol = objc_getProtocol("EatProtocol");
SEL selector = sel_registerName("test");
const char* type = "v@:";
BOOL isRequiredMethod = YES;
BOOL isInstanceMethod = YES;
protocol_addMethodDescription(eatProtocol, selector, type, isRequiredMethod, isInstanceMethod);
struct objc_method_description method = protocol_getMethodDescription(eatProtocol, sel_registerName("test"), YES, YES);
NSLog(@"test方法 name = %s,types = %s", sel_getName(method.name) ,method.types);
}
复制代码运行结果：
objc[2121]: protocol_addMethodDescription: protocol 'EatProtocol' is not under construction!
2019-03-01 09:30:56.232714+0800 Runtime-Demo[2121:6266526] test方法 name = <null selector>,types = (null)
复制代码打印结果说EatProtocol不在建设中，添加方法也失败！ 第二种情况：
-(void)addMethodDescription2 {
Protocol* protocol = objc_allocateProtocol("TestProtocol");
SEL selector = sel_registerName("test");
const char* type = "v@:";
BOOL isRequiredMethod = YES;
BOOL isInstanceMethod = YES;
protocol_addMethodDescription(protocol, selector, type, isRequiredMethod, isInstanceMethod);
objc_registerProtocol(protocol);
struct objc_method_description method = protocol_getMethodDescription(protocol, sel_registerName("test"), YES, YES);
NSLog(@"test方法 name = %s,types = %s", sel_getName(method.name) ,method.types);
}
复制代码运行结果：
2019-03-01 09:32:34.581517+0800 Runtime-Demo[2148:6267322] test方法 name = test,types = v@:
复制代码下面这个方法是添加属性：
void
protocol_addProperty(Protocol * _Nonnull proto, const char * _Nonnull name,
const objc_property_attribute_t * _Nullable attributes,
unsigned int attributeCount,
BOOL isRequiredProperty, BOOL isInstanceProperty)
OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0, 2.0);
复制代码这个函数和protocol_addMethodDescription一样，只有通过objc_allocateProtocol生成的协议才能添加属性。
-(void)addProperty_protocol {
Protocol* protocol = objc_allocateProtocol("TestProtocol");
const char* name = "juice";
unsigned int count = 5;
objc_property_attribute_t attributeList[count];
objc_property_attribute_t attribute1 ;
attribute1.name = "T";
attribute1.value = "NSString";
objc_property_attribute_t attribute2 ;
attribute2.name = "V";
attribute2.value = "_juice";
objc_property_attribute_t attribute3 ;
attribute3.name = "N";
attribute3.value = "";
objc_property_attribute_t attribute4 ;
attribute4.name = "C";
attribute4.value = "";
objc_property_attribute_t attribute5 ;
attribute5.name = "R";
attribute5.value = "";
attributeList[0] = attribute1;
attributeList[1] = attribute2;
attributeList[2] = attribute3;
attributeList[3] = attribute4;
attributeList[4] = attribute5;
BOOL isRequiredProperty = YES;
BOOL isInstanceProperty = YES;
protocol_addProperty(protocol, name, (const objc_property_attribute_t*)attributeList, count, isRequiredProperty, isInstanceProperty);
objc_registerProtocol(protocol);
objc_property_t property = protocol_getProperty(protocol, "juice", YES, YES);
NSLog(@"name = %s",property_getName(property));
}
复制代码运行结果：
name = juice
复制代码下面的函数是指的是让proto协议遵循addition协议。
void
protocol_addProtocol(Protocol * _Nonnull proto, Protocol * _Nonnull addition)
OBJC_AVAILABLE(10.7, 4.3, 9.0, 1.0, 2.0);
复制代码proto协议必须是仍在构建当中（alloc但是没有register）而addition是要已经构建好的。我们让TestProtocol遵循SingProtocol协议。
-(void)addProtocol_protocol {
Protocol* protocol = objc_allocateProtocol("TestProtocol");
Protocol* protocol2 = objc_getProtocol("SingProtocol");
protocol_addProtocol(protocol, protocol2);
objc_registerProtocol(protocol);
BOOL isConform = protocol_conformsToProtocol(protocol, protocol2);
NSLog(@"isConform = %d",isConform);
}
复制代码运行结果：
isConform = 1
复制代码下面这个方法是让一个类遵循protocol协议
BOOL
class_addProtocol(Class _Nullable cls, Protocol * _Nonnull protocol)
OBJC_AVAILABLE(10.5, 2.0, 9.0, 1.0, 2.0);
复制代码目前Cat类没有遵循任何协议，这里我打算让Cat遵循PlayProtocol协议：
-(void)addProtocol_class {
Protocol* protocol = objc_getProtocol("PlayProtocol");
Class class = objc_getClass("Cat");
class_addProtocol(class, protocol);
BOOL isConform = class_conformsToProtocol(class, protocol);
NSLog(@"isConform = %d",isConform);
}
复制代码运行结果：
isConform = 1
复制代码这样，所有关于Protocol的方法都测试完成了。