YTKNetwork解析

YTKNetwork是猿题库 iOS 研发团队基于 AFNetworking 封装的 iOS 网络库,提供了更高层次的网络访问抽象。
相比于AFNetworking,YTKNetwork提供了更高级的功能
·支持按时间缓存网络请求内容
·支持按版本号缓存网络请求内容
·支持统一设置服务器和 CDN 的地址
·支持检查返回 JSON 内容的合法性
·支持文件的断点续传
·支持 block 和 delegate 两种模式的回调方式
·支持批量的网络请求发送,并统一设置它们的回调(实现在 YTKBatchRequest 类中)
·支持方便地设置有相互依赖的网络请求的发送,例如:发送请求 A,根据请求 A 的结果,选择性·的发送请求 B 和 C,再根据 B 和 C 的结果,选择性的发送请求 D。(实现在 YTKChainRequest 类中)
·支持网络请求 URL 的 filter,可以统一为网络请求加上一些参数,或者修改一些路径。
定义了一套插件机制,可以很方便地为 YTKNetwork 增加功能。猿题库官方现在提供了一个插件,可以在某些网络请求发起时,在界面上显示“正在加载”的 HUD。
YTKNetwork使用了设计模式里面的command模式,简单来说,就是把请求封装成一个对象,使需要请求的类与第三方底层网络分开,降低耦合性,也方便了我们更换网络库。同时也方便处理一些处理公共逻辑和对象的持久化。

接下来我们来看看YTK是怎么工作的。
在github的基础教程里面我们可以看到YTK是把每个网络请求都封装成对象,所以我们每个请求都需要继承YTKRequest,通过重写父类的方法来构造我们想要的网络请求,所以我们来重写一下YTKRequest从而进行一个网络请求

#import <YTKNetwork/YTKNetwork.h>

@interface ZJRequest : YTKRequest

@end

#import "ZJRequest.h"

@implementation ZJRequest

  - (NSString *)requestUrl
{
    return @"/api/4/news/latest";
}

- (YTKRequestMethod)requestMethod
{
    return YTKRequestMethodGET;
}

- (id)requestArgument
{
    return @{};
}
@end

这里我们requestUrl去掉了域名信息,因为域名信息我们已经在AppDelegate利用YTKNetworkConfig设置过域名。

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
     YTKNetworkConfig *config = [YTKNetworkConfig sharedConfig];
    config.baseUrl = @"https://news-at.zhihu.com";
    return YES;
}

上述代码我们重写了参数和请求方式方法,使用GET方法来请求。
我们构造完成ZJRequest之后,来我们需要网络请求的ViewController,调用我们的ZJRequest,并使用block来取得网络请求结果

 ZJRequest *request = [[ZJRequest alloc]init];
    [request startWithCompletionBlockWithSuccess:^(__kindof YTKBaseRequest * _Nonnull request) {
        NSLog(@"succeed");
    } failure:^(__kindof YTKBaseRequest * _Nonnull request) {
        NSLog(@"failure");
    }];

除此之外,YTKNetwork还支持delegate回调

- (void)viewDidLoad {
    [super viewDidLoad];
    ZJRequest *request = [[ZJRequest alloc]init];
//    [request startWithCompletionBlockWithSuccess:^(__kindof YTKBaseRequest * _Nonnull request) {
//        NSLog(@"succeed");
//    } failure:^(__kindof YTKBaseRequest * _Nonnull request) {
//        NSLog(@"failure");
//    }];
    
    request.delegate = self;
    [request start];
}
- (void)requestFinished:(YTKBaseRequest *)request {
    NSLog(@"succeed");
}
- (void)requestFailed:(YTKBaseRequest *)request {
    NSLog(@"failed");
}

我们先从startWithCompletionBlockWithSuccess:failure点进去看看里面的实现

- (void)startWithCompletionBlockWithSuccess:(YTKRequestCompletionBlock)success
                                    failure:(YTKRequestCompletionBlock)failure {
    [self setCompletionBlockWithSuccess:success failure:failure];
    [self start];
}

YTK先设置了成功的block和失败的回调,具体是用setter方法把YTKBaseRequest里面的successCompletionBlockfailureCompletionBlock赋值进去

- (void)setCompletionBlockWithSuccess:(YTKRequestCompletionBlock)success
                              failure:(YTKRequestCompletionBlock)failure {
    self.successCompletionBlock = success;
    self.failureCompletionBlock = failure;
}

接下来调用start方法,此处先调用YTKRequest的start方法

- (void)start {
    //是否忽略响应缓存
    if (self.ignoreCache) {
        [self startWithoutCache];
        return;
    }

    //是否有待恢复的下载请求
    if (self.resumableDownloadPath) {
        [self startWithoutCache];
        return;
    }
    //是否有错误的缓存
    if (![self loadCacheWithError:nil]) {
        [self startWithoutCache];
        return;
    }
    
    _dataFromCache = YES;

    dispatch_async(dispatch_get_main_queue(), ^{
        [self requestCompletePreprocessor];
        [self requestCompleteFilter];
        YTKRequest *strongSelf = self;
        [strongSelf.delegate requestFinished:strongSelf];
        if (strongSelf.successCompletionBlock) {
            strongSelf.successCompletionBlock(strongSelf);
        }
        [strongSelf clearCompletionBlock];
    });
}

YTK使用了三个判断,都是是否需要进行无缓存的请求
如果我们的缓存里面已经有响应了,YTK就会调用requestCompletePreprocessorrequestCompleteFilter两个方法,但这两个方法都是留给我们去实现,YTK并没有实现,然后并调用了自身的完成回调并传递为成功回调
我们先假设缓存为nil,进入startWithoutCache看看

- (void)startWithoutCache {
    //先清除所有缓存的变量
    [self clearCacheVariables];
    [super start];
}
- (void)clearCacheVariables {
    _cacheData = nil;//
    _cacheXML = nil;
    _cacheJSON = nil;
    _cacheString = nil;
    _cacheMetadata = nil;
    _dataFromCache = NO;
}

YTK先清除缓存的所有变量,包括响应的Data数据,XML,JSON,String,元Data,还有一个布尔值,方便我们做响应的存储,分别对应各种数据格式
接下来调用父类YTKBaseRequest的重点方法start

- (void)start {
    [self toggleAccessoriesWillStartCallBack];
    [[YTKNetworkAgent sharedAgent] addRequest:self];
}
- (void)toggleAccessoriesWillStartCallBack {
    for (id<YTKRequestAccessory> accessory in self.requestAccessories) {
        if ([accessory respondsToSelector:@selector(requestWillStart:)]) {
            [accessory requestWillStart:self];
        }
    }
}

第一个方法就是调用协议里面的requestWillStart:来通知请求即将开始。其中self.requestAccessories是YTKBaseRequest定义的一个可变数组,用来储存协议YTKRequestAccessory,第二个方法即是通过YTKNetworkAgent的单例调用addRequest方法
我们来看这个单例是什么

+ (YTKNetworkAgent *)sharedAgent {
    static id sharedInstance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedInstance = [[self alloc] init];
    });
    return sharedInstance;
}

- (instancetype)init {
    self = [super init];
    if (self) {
        _config = [YTKNetworkConfig sharedConfig];
        _manager = [[AFHTTPSessionManager alloc] initWithSessionConfiguration:_config.sessionConfiguration];
        _requestsRecord = [NSMutableDictionary dictionary];
        _processingQueue = dispatch_queue_create("com.yuantiku.networkagent.processing", DISPATCH_QUEUE_CONCURRENT);
        _allStatusCodes = [NSIndexSet indexSetWithIndexesInRange:NSMakeRange(100, 500)];
        pthread_mutex_init(&_lock, NULL);

        _manager.securityPolicy = _config.securityPolicy;
        _manager.responseSerializer = [AFHTTPResponseSerializer serializer];
        // Take over the status code validation
        _manager.responseSerializer.acceptableStatusCodes = _allStatusCodes;
        _manager.completionQueue = _processingQueue;
    }
    return self;
}

这个类包括创建了YTKNetworkConfig的单例,还有AFHTTPSessionManager的实例并把单例内的sessionConfig传进AFHTTPSessionManager,还有相应的安全政策,设定可接受响应码,并创建了一个并行队列设置为AF的完成队列和互斥锁lock
然后我们进入addRequest:这个方法

- (void)addRequest:(YTKBaseRequest *)request {
    //参数判断request不能为空
    NSParameterAssert(request != nil);
    
    NSError * __autoreleasing requestSerializationError = nil;
    //这里如果我们设置了url就直接用url请求
    NSURLRequest *customUrlRequest= [request buildCustomUrlRequest];
    if (customUrlRequest) {
        __block NSURLSessionDataTask *dataTask = nil;
        //调用AF请求
        dataTask = [_manager dataTaskWithRequest:customUrlRequest completionHandler:^(NSURLResponse * _Nonnull response, id  _Nullable responseObject, NSError * _Nullable error) {
            [self handleRequestResult:dataTask responseObject:responseObject error:error];
        }];
        request.requestTask = dataTask;
    } else {
        //如果没有,则创建
        request.requestTask = [self sessionTaskForRequest:request error:&requestSerializationError];
    }

    if (requestSerializationError) {
        [self requestDidFailWithRequest:request error:requestSerializationError];
        return;
    }

    NSAssert(request.requestTask != nil, @"requestTask should not be nil");

    // Set request task priority
    // !!Available on iOS 8 +
    //设置请求的优先级
    if ([request.requestTask respondsToSelector:@selector(priority)]) {
        switch (request.requestPriority) {
            case YTKRequestPriorityHigh:
                request.requestTask.priority = NSURLSessionTaskPriorityHigh;
                break;
            case YTKRequestPriorityLow:
                request.requestTask.priority = NSURLSessionTaskPriorityLow;
                break;
            case YTKRequestPriorityDefault:
                /*!!fall through*/
            default:
                request.requestTask.priority = NSURLSessionTaskPriorityDefault;
                break;
        }
    }

    // Retain request
    YTKLog(@"Add request: %@", NSStringFromClass([request class]));
    //绑定request的id,这里跟AF的思想是一样的,用一个字典存储请求,并设置一个id为key
    [self addRequestToRecord:request];
    [request.requestTask resume];
}

这里面涉及的方法很多,我们来一个一个看
首先YTK先获取CustomRequest,如果我们重写了一个request则直接调用AF请求,并设置响应内容调用了handleRequestResult:responseObject:error,记录了dataTask。反之,则用request的参数通过sessionTaskRequest:error自己生成了一个requestTask,再用requestRecord记录了这个request,最后resume这个task。
AF的方法在这就暂不描述,感兴趣可以看这篇AFNetworking解析,它做了什么
我们来看回调里面YTK调用的方法

- (void)handleRequestResult:(NSURLSessionTask *)task responseObject:(id)responseObject error:(NSError *)error {
    //避免多线程下取到的request不一致,这里用了线程锁
    Lock();
    YTKBaseRequest *request = _requestsRecord[@(task.taskIdentifier)];
    Unlock();

    //在AF中,request如果被取消或者在record里被删除,将会调用失败回调,在YTK则直接返回,  
     不做回调
    if (!request) {
        return;
    }

    YTKLog(@"Finished Request: %@", NSStringFromClass([request class]));

    NSError * __autoreleasing serializationError = nil;
    NSError * __autoreleasing validationError = nil;

    NSError *requestError = nil;
    BOOL succeed = NO;
    //获取响应内容,序列化内容
    request.responseObject = responseObject;
    if ([request.responseObject isKindOfClass:[NSData class]]) {
        request.responseData = responseObject;
        //根据响应内容的编码做转换,其中调用了AF2.6.3中方法
        request.responseString = [[NSString alloc] initWithData:responseObject encoding:[YTKNetworkUtils stringEncodingWithRequest:request]];
        //判断序列化方式
        switch (request.responseSerializerType) {
            case YTKResponseSerializerTypeHTTP:
                // Default serializer. Do nothing.
                break;
            case YTKResponseSerializerTypeJSON:
                request.responseObject = [self.jsonResponseSerializer responseObjectForResponse:task.response data:request.responseData error:&serializationError];
                request.responseJSONObject = request.responseObject;
                break;
            case YTKResponseSerializerTypeXMLParser:
                request.responseObject = [self.xmlParserResponseSerialzier responseObjectForResponse:task.response data:request.responseData error:&serializationError];
                break;
        }
    }
    if (error) {
        succeed = NO;
        requestError = error;
    } else if (serializationError) {
        succeed = NO;
        requestError = serializationError;
    } else {
        succeed = [self validateResult:request error:&validationError];
        requestError = validationError;
    }

    if (succeed) {
        [self requestDidSucceedWithRequest:request];
    } else {
        [self requestDidFailWithRequest:request error:requestError];
    }

    dispatch_async(dispatch_get_main_queue(), ^{
        [self removeRequestFromRecord:request];
        //YTK在这里把回调都置为nil,从而打破循环引用,所以我们可以直接在最开始的startWithCompletionBlockWithSuccess:failure:里面的block直接使用self
        [request clearCompletionBlock];
    });
}

这段代码很容易看懂,就是获取到响应内容,并做序列化,最后再返回序列化后的内容
其中我们可以通过重写YTK的responseSerializerType分别对数据进行解析,分为HTTP(不做处理),JSON,XML,使用的都是AF里面的方法。YTK最后还对响应的内容做了合法化判断(如果你重写了jsonValidator),我们可以看看这个方法做了什么

- (BOOL)validateResult:(YTKBaseRequest *)request error:(NSError * _Nullable __autoreleasing *)error {
    //判断响应码是否在200~299
    BOOL result = [request statusCodeValidator];
    if (!result) {
        if (error) {
            *error = [NSError errorWithDomain:YTKRequestValidationErrorDomain code:YTKRequestValidationErrorInvalidStatusCode userInfo:@{NSLocalizedDescriptionKey:@"Invalid status code"}];
        }
        return result;
    }
    id json = [request responseJSONObject];
    id validator = [request jsonValidator];
    //获取响应的json和需要验证的字段
    if (json && validator) {
        result = [YTKNetworkUtils validateJSON:json withValidator:validator];
        if (!result) {
            if (error) {
                *error = [NSError errorWithDomain:YTKRequestValidationErrorDomain code:YTKRequestValidationErrorInvalidJSONFormat userInfo:@{NSLocalizedDescriptionKey:@"Invalid JSON format"}];
            }
            return result;
        }
    }
    return YES;
}

我们接着看validateJSON:withValidator:

+ (BOOL)validateJSON:(id)json withValidator:(id)jsonValidator {
  if ([json isKindOfClass:[NSDictionary class]] &&
        [jsonValidator isKindOfClass:[NSDictionary class]]) {
        NSDictionary * dict = json;
        NSDictionary * validator = jsonValidator;
        BOOL result = YES;
        NSEnumerator * enumerator = [validator keyEnumerator];
        NSString * key;
        while ((key = [enumerator nextObject]) != nil) {
            id value = dict[key];
            id format = validator[key];
            if ([value isKindOfClass:[NSDictionary class]]
                || [value isKindOfClass:[NSArray class]]) {
                result = [self validateJSON:value withValidator:format];
                if (!result) {
                    break;
                }
            } else {
                if ([value isKindOfClass:format] == NO &&
                    [value isKindOfClass:[NSNull class]] == NO) {
                    result = NO;
                    break;
                }
            }
        }
        return result;
    } else if ([json isKindOfClass:[NSArray class]] &&
               [jsonValidator isKindOfClass:[NSArray class]]) {
        NSArray * validatorArray = (NSArray *)jsonValidator;
        if (validatorArray.count > 0) {
            NSArray * array = json;
            NSDictionary * validator = jsonValidator[0];
            for (id item in array) {
                BOOL result = [self validateJSON:item withValidator:validator];
                if (!result) {
                    return NO;
                }
            }
        }
        return YES;
    } else if ([json isKindOfClass:jsonValidator]) {
        return YES;
    } else {
        return NO;
    }

这个方法就是递归调用遍历jsonValidator和json看数据类型是否跟我们要求的一样,方法很简单清晰

我们再回到handleRequestResult:responseObject:error:这个方法里面

if (succeed) {
        [self requestDidSucceedWithRequest:request];
    } else {
        [self requestDidFailWithRequest:request error:requestError];
    }

我们来看succeed为YES的时候YTK做了什么

- (void)requestDidSucceedWithRequest:(YTKBaseRequest *)request {
    @autoreleasepool {
        [request requestCompletePreprocessor];
    }
    dispatch_async(dispatch_get_main_queue(), ^{
        [request toggleAccessoriesWillStopCallBack];
        [request requestCompleteFilter];

        if (request.delegate != nil) {
            [request.delegate requestFinished:request];
        }
        if (request.successCompletionBlock) {
            request.successCompletionBlock(request);
        }
        [request toggleAccessoriesDidStopCallBack];
    });
}
- (void)requestCompletePreprocessor {
    [super requestCompletePreprocessor];
    //是否要异步写入缓存
    if (self.writeCacheAsynchronously) {
        //创建了一个异步队列单例
        dispatch_async(ytkrequest_cache_writing_queue(), ^{
            [self saveResponseDataToCacheFile:[super responseData]];
        });
    } else {
        [self saveResponseDataToCacheFile:[super responseData]];
    }
}

当succeed为YES的时候YTK首先调用了requestCompletePreprocessor把请求回来的数据做了一个缓存,然后调用requestWillStop:requestCompleteFilter,这两个方法都没有具体的实现,是想我们自己实现吧,接下来分别调用requestFinished和成功完成的回调和协议。

我们来看YTK是如何做缓存的,缓存策略是什么

- (void)saveResponseDataToCacheFile:(NSData *)data {
     //缓存时间存在和要缓存的数据不是来自缓存
    if ([self cacheTimeInSeconds] > 0 && ![self isDataFromCache]) {
        if (data != nil) {
            @try {
               这里开始写入数据
                [data writeToFile:[self cacheFilePath] atomically:YES];
                YTKCacheMetadata *metadata = [[YTKCacheMetadata alloc] init];
                metadata.version = [self cacheVersion];
                metadata.sensitiveDataString = ((NSObject *)[self cacheSensitiveData]).description;
                metadata.stringEncoding = [YTKNetworkUtils stringEncodingWithRequest:self];
                metadata.creationDate = [NSDate date];
                metadata.appVersionString = [YTKNetworkUtils appVersionString];
                [NSKeyedArchiver archiveRootObject:metadata toFile:[self cacheMetadataFilePath]];
            } @catch (NSException *exception) {
                YTKLog(@"Save cache failed, reason = %@", exception.reason);
            }
        }
    }
}

- (NSString *)cacheBasePath {
    NSString *pathOfLibrary = [NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *path = [pathOfLibrary stringByAppendingPathComponent:@"LazyRequestCache"];

     //如果自定义了缓存地址,则使用自定义地址缓存
    NSArray<id<YTKCacheDirPathFilterProtocol>> *filters = [[YTKNetworkConfig sharedConfig] cacheDirPathFilters];
    if (filters.count > 0) {
        for (id<YTKCacheDirPathFilterProtocol> f in filters) {
            path = [f filterCacheDirPath:path withRequest:self];
        }
    }

    [self createDirectoryIfNeeded:path];
    return path;
}
- (void)createDirectoryIfNeeded:(NSString *)path {
    NSFileManager *fileManager = [NSFileManager defaultManager];
    BOOL isDir;
    //如果没有这个文件就直接创建,有的话就先移除再创建
    if (![fileManager fileExistsAtPath:path isDirectory:&isDir]) {
        [self createBaseDirectoryAtPath:path];
    } else {
        if (!isDir) {
            NSError *error = nil;
            [fileManager removeItemAtPath:path error:&error];
            [self createBaseDirectoryAtPath:path];
        }
    }
}
- (void)createBaseDirectoryAtPath:(NSString *)path {
    NSError *error = nil;
    [[NSFileManager defaultManager] createDirectoryAtPath:path withIntermediateDirectories:YES
                                               attributes:nil error:&error];
    if (error) {
        YTKLog(@"create cache directory failed, error = %@", error);
    } else {
        //禁止icloud备份
        [YTKNetworkUtils addDoNotBackupAttribute:path];
    }
}
- (NSString *)cacheFileName {
    NSString *requestUrl = [self requestUrl];
    NSString *baseUrl = [YTKNetworkConfig sharedConfig].baseUrl;
    id argument = [self cacheFileNameFilterForRequestArgument:[self requestArgument]];
    NSString *requestInfo = [NSString stringWithFormat:@"Method:%ld Host:%@ Url:%@ Argument:%@",
                             (long)[self requestMethod], baseUrl, requestUrl, argument];
    NSString *cacheFileName = [YTKNetworkUtils md5StringFromString:requestInfo];
    return cacheFileName;
}

- (NSString *)cacheFilePath {
    NSString *cacheFileName = [self cacheFileName];
    NSString *path = [self cacheBasePath];
    path = [path stringByAppendingPathComponent:cacheFileName];
    return path;
}

- (NSString *)cacheMetadataFilePath {
    NSString *cacheMetadataFileName = [NSString stringWithFormat:@"%@.metadata", [self cacheFileName]];
    NSString *path = [self cacheBasePath];
    path = [path stringByAppendingPathComponent:cacheMetadataFileName];
    return path;
}

YTK缓存文件名由请求方法,完整的url地址和参数,并做md5变换。先创建地址名为“LazyRequestCache”缓存的文件夹,最后再把数据写进文件。然后把创建了一个YTKCacheMetadata的实例,专门用来储存当前这个缓存的附加信息,也存在了跟data相同的文件夹里面

接下来来看Succeed为NO的时候

- (void)requestDidFailWithRequest:(YTKBaseRequest *)request error:(NSError *)error {
    request.error = error;
    //先打印错误信息
    YTKLog(@"Request %@ failed, status code = %ld, error = %@",
           NSStringFromClass([request class]), (long)request.responseStatusCode, error.localizedDescription);

     //如果是下载的数据,则先对下载的数据做缓存。因为可能是序列化数据的时候出现了问题,所以先对下载的数据做缓存,其中resumeableDownloadPath的为自定义路径,提供恢复下载的地址
    NSData *incompleteDownloadData = error.userInfo[NSURLSessionDownloadTaskResumeData];
    if (incompleteDownloadData) {
        [incompleteDownloadData writeToURL:[self incompleteDownloadTempPathForDownloadPath:request.resumableDownloadPath] atomically:YES];
    }
  //如果下载中断,则对url进行缓存
    if ([request.responseObject isKindOfClass:[NSURL class]]) {
        NSURL *url = request.responseObject;
        if (url.isFileURL && [[NSFileManager defaultManager] fileExistsAtPath:url.path]) {
            request.responseData = [NSData dataWithContentsOfURL:url];
            request.responseString = [[NSString alloc] initWithData:request.responseData encoding:[YTKNetworkUtils stringEncodingWithRequest:request]];

            [[NSFileManager defaultManager] removeItemAtURL:url error:nil];
        }
        request.responseObject = nil;
    }

    @autoreleasepool {
        [request requestFailedPreprocessor];
    }
    dispatch_async(dispatch_get_main_queue(), ^{
        [request toggleAccessoriesWillStopCallBack];
        [request requestFailedFilter];

        if (request.delegate != nil) {
            [request.delegate requestFailed:request];
        }
        if (request.failureCompletionBlock) {
            request.failureCompletionBlock(request);
        }
        [request toggleAccessoriesDidStopCallBack];
    });
}

总的来说,如果有下载的数据,就先做缓存,下载失败,则缓存url。最后在分别调用requestFailedPreprocessorrequestFailedFilter,具体实现YTK留给用户实现,然后调用失败回调。

回到我们的addRequest:方法里面

  if (customUrlRequest) {
        __block NSURLSessionDataTask *dataTask = nil;
        dataTask = [_manager dataTaskWithRequest:customUrlRequest completionHandler:^(NSURLResponse * _Nonnull response, id  _Nullable responseObject, NSError * _Nullable error) {
            [self handleRequestResult:dataTask responseObject:responseObject error:error];
        }];
        request.requestTask = dataTask;
    } else {
        request.requestTask = [self sessionTaskForRequest:request error:&requestSerializationError];
    }

我们来看YTK创建requestTask的方法

- (NSURLSessionTask *)sessionTaskForRequest:(YTKBaseRequest *)request error:(NSError * _Nullable __autoreleasing *)error {
    //获取request必要的参数
    YTKRequestMethod method = [request requestMethod];
    NSString *url = [self buildRequestUrl:request];
    id param = request.requestArgument;
    //此处block是为了上传图片等附件形式
    AFConstructingBlock constructingBlock = [request constructingBodyBlock];
    AFHTTPRequestSerializer *requestSerializer = [self requestSerializerForRequest:request];

    switch (method) {
        case YTKRequestMethodGET:
            if (request.resumableDownloadPath) {
                return [self downloadTaskWithDownloadPath:request.resumableDownloadPath requestSerializer:requestSerializer URLString:url parameters:param progress:request.resumableDownloadProgressBlock error:error];
            } else {
                return [self dataTaskWithHTTPMethod:@"GET" requestSerializer:requestSerializer URLString:url parameters:param error:error];
            }
        case YTKRequestMethodPOST:
            return [self dataTaskWithHTTPMethod:@"POST" requestSerializer:requestSerializer URLString:url parameters:param constructingBodyWithBlock:constructingBlock error:error];
        case YTKRequestMethodHEAD:
            return [self dataTaskWithHTTPMethod:@"HEAD" requestSerializer:requestSerializer URLString:url parameters:param error:error];
        case YTKRequestMethodPUT:
            return [self dataTaskWithHTTPMethod:@"PUT" requestSerializer:requestSerializer URLString:url parameters:param error:error];
        case YTKRequestMethodDELETE:
            return [self dataTaskWithHTTPMethod:@"DELETE" requestSerializer:requestSerializer URLString:url parameters:param error:error];
        case YTKRequestMethodPATCH:
            return [self dataTaskWithHTTPMethod:@"PATCH" requestSerializer:requestSerializer URLString:url parameters:param error:error];
    }
}

前面是获取request的一些必要参数,在获取url的获取,YTK用了一个方法buildRequestUrl:,里面做了对Url的合法性判断,还有是否需要cdn加速。接下来获取了request的序列化类的实例,并准备开始请求。我们先来看dataTaskWithHTTPMethod:requestSerializer:URLString:parameters:error:这个通用方法,YTK传入了请求方法、序列化方式、参数和url,如果为post方法还加入了constructingBlock。

- (NSURLSessionDataTask *)dataTaskWithHTTPMethod:(NSString *)method
                               requestSerializer:(AFHTTPRequestSerializer *)requestSerializer
                                       URLString:(NSString *)URLString
                                      parameters:(id)parameters
                                           error:(NSError * _Nullable __autoreleasing *)error {
    return [self dataTaskWithHTTPMethod:method requestSerializer:requestSerializer URLString:URLString parameters:parameters constructingBodyWithBlock:nil error:error];
}

- (NSURLSessionDataTask *)dataTaskWithHTTPMethod:(NSString *)method
                               requestSerializer:(AFHTTPRequestSerializer *)requestSerializer
                                       URLString:(NSString *)URLString
                                      parameters:(id)parameters
                       constructingBodyWithBlock:(nullable void (^)(id <AFMultipartFormData> formData))block
                                           error:(NSError * _Nullable __autoreleasing *)error {
    NSMutableURLRequest *request = nil;
    
    if (block) {
        //如果有文件上传则调用文件上传的请求方法
        request = [requestSerializer multipartFormRequestWithMethod:method URLString:URLString parameters:parameters constructingBodyWithBlock:block error:error];
    } else {
        request = [requestSerializer requestWithMethod:method URLString:URLString parameters:parameters error:error];
    }

    __block NSURLSessionDataTask *dataTask = nil;
    dataTask = [_manager dataTaskWithRequest:request
                           completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *_error) {
                               [self handleRequestResult:dataTask responseObject:responseObject error:_error];
                           }];

    return dataTask;
}

如果是文件上传的方式,则调用AF的文件上传方法,反之,则使用普通的请求方式。

总结,YTKbaseRequest就是把我们每个请求都封装成一个对象,具体的实现请求都交给了AFNetworking。代码还是结构还是很清晰的,阅读难度也不大

接下我们来看YTK的YTKBatchRequest类
YTKBatchRequest可以统一处理多个请求
用法如下


- (void)sendBatchRequest {
    GetImageApi *a = [[GetImageApi alloc] initWithImageId:@"1.jpg"];
    GetImageApi *b = [[GetImageApi alloc] initWithImageId:@"2.jpg"];
    GetImageApi *c = [[GetImageApi alloc] initWithImageId:@"3.jpg"];
    GetUserInfoApi *d = [[GetUserInfoApi alloc] initWithUserId:@"123"];
    YTKBatchRequest *batchRequest = [[YTKBatchRequest alloc] initWithRequestArray:@[a, b, c, d]];
    [batchRequest startWithCompletionBlockWithSuccess:^(YTKBatchRequest *batchRequest) {
        NSLog(@"succeed");
        NSArray *requests = batchRequest.requestArray;
        GetImageApi *a = (GetImageApi *)requests[0];
        GetImageApi *b = (GetImageApi *)requests[1];
        GetImageApi *c = (GetImageApi *)requests[2];
        GetUserInfoApi *user = (GetUserInfoApi *)requests[3];
        // deal with requests result ...
    } failure:^(YTKBatchRequest *batchRequest) {
        NSLog(@"failed");
    }];
}

我们来看下init方法

- (instancetype)initWithRequestArray:(NSArray<YTKRequest *> *)requestArray {
    self = [super init];
    if (self) {
        _requestArray = [requestArray copy];
        _finishedCount = 0;
        for (YTKRequest * req in _requestArray) {
            if (![req isKindOfClass:[YTKRequest class]]) {
                YTKLog(@"Error, request item must be YTKRequest instance.");
                return nil;
            }
        }
    }
    return self;
}

初始化方法中,先取得request的数组requestArray,并且设置完成请求数量finishCount为0。
接下来来看

- (void)startWithCompletionBlockWithSuccess:(void (^)(YTKBatchRequest *batchRequest))success
                                    failure:(void (^)(YTKBatchRequest *batchRequest))failure {
    [self setCompletionBlockWithSuccess:success failure:failure];
    [self start];
}

- (void)setCompletionBlockWithSuccess:(void (^)(YTKBatchRequest *batchRequest))success
                              failure:(void (^)(YTKBatchRequest *batchRequest))failure {
    self.successCompletionBlock = success;
    self.failureCompletionBlock = failure;
}

跟YTKBaseRequest一样,都是先设置好回调的Block,再调用start方法

- (void)start
  if (_finishedCount > 0) {
        YTKLog(@"Error! Batch request has already started.");
        return;
    }
    _failedRequest = nil;
    [[YTKBatchRequestAgent sharedAgent] addBatchRequest:self];
    [self toggleAccessoriesWillStartCallBack];
    for (YTKRequest * req in _requestArray) {
        req.delegate = self;
        [req clearCompletionBlock];
        [req start];
    }

先判断时候有正在进行的request,如果有就返回,没有的话,遍历requestArray里面的内容,并开始请求,并设置了delegate
我们来看回调

- (void)requestFinished:(YTKRequest *)request {
    _finishedCount++;
    if (_finishedCount == _requestArray.count) {
        [self toggleAccessoriesWillStopCallBack];
        if ([_delegate respondsToSelector:@selector(batchRequestFinished:)]) {
            [_delegate batchRequestFinished:self];
        }
        if (_successCompletionBlock) {
            _successCompletionBlock(self);
        }
        [self clearCompletionBlock];
        [self toggleAccessoriesDidStopCallBack];
        [[YTKBatchRequestAgent sharedAgent] removeBatchRequest:self];
    }
}

- (void)requestFailed:(YTKRequest *)request {
    _failedRequest = request;
    [self toggleAccessoriesWillStopCallBack];
    // Stop
    for (YTKRequest *req in _requestArray) {
        [req stop];
    }
    // Callback
    if ([_delegate respondsToSelector:@selector(batchRequestFailed:)]) {
        [_delegate batchRequestFailed:self];
    }
    if (_failureCompletionBlock) {
        _failureCompletionBlock(self);
    }
    // Clear
    [self clearCompletionBlock];

    [self toggleAccessoriesDidStopCallBack];
    [[YTKBatchRequestAgent sharedAgent] removeBatchRequest:self];
}

- (void)clearRequest {
    for (YTKRequest * req in _requestArray) {
        [req stop];
    }
    [self clearCompletionBlock];
}

当所有请求完成并成功,返回所有request,并清除block。里面利用finishCount来判断是否请求都完成,如果是有一个请求失败的话,则暂停所有请求,返回失败回调。

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