AFNetworking 2.0 出现Use of undeclared identifier AFURLSessionManager错误

当向下面使用时会出现错误

#import "AFNetworking.h"
#import "AFURLSessionManager.h"

AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];

主要原因是NSURLSession模块仅支持ios7，打开AFURLSessionManager.h会看到一个宏

#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED >= 70000) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1090)

AFURLSessionManager只支持ios7和macosx10.9.0故创建下载任务时

-(void)download:(NSString *)url complete:(void(^)(id result,NSError *error))success{
#if (defined(__IPHONE_OS_VERSION_MIN_REQUIRED) && __IPHONE_OS_VERSION_MIN_REQUIRED >= 70000) || (defined(__MAC_OS_X_VERSION_MIN_REQUIRED) && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1090)
    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];

    AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];

    NSURL *URL = [NSURL URLWithString:url];
    NSURLRequest *request = [NSURLRequest requestWithURL:URL];

    NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:nil destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
        NSURL *documentsDirectoryPath = [NSURL fileURLWithPath:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject]];
        return [documentsDirectoryPath URLByAppendingPathComponent:[targetPath lastPathComponent]];
    } completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
        NSLog(@"File downloaded to: %@", filePath);
        if (error) {
            success(nil,error);
        }else{
            success(filePath,nil);
        }
    }];
    [downloadTask resume];
#else
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *path = [[paths objectAtIndex:] stringByAppendingPathComponent:[url lastPathComponent]];
    operation.outputStream = [NSOutputStream outputStreamToFileAtPath:path append:NO];
    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
        NSLog(@"Successfully downloaded file to %@", path);
         success(path,nil);
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        NSLog(@"Error: %@", error);
        success(nil,error);
    }];
    [operation start];
#endif
}