iOS之runtime详解api(四)

系统管理员 2022-01-20 05:23 197阅读 0赞

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
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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");
    }
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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);
    }
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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);
    
    }
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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));
    }
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运行结果：

TestProtocol
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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);
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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);
    }
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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)
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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);
    }
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运行结果：

2019-03-01 09:32:34.581517+0800 Runtime-Demo[2148:6267322] test方法 name = test,types = v@:
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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);
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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));
    }
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运行结果：

name = juice
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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);
    }
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运行结果：

isConform = 1
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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
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这样，所有关于`Protocol`的方法都测试完成了。