iOS 解析如何通过 URL 下载文件

Question

我正在为我的聊天应用程序使用解析。当我上传文件时，我保留 url，并将 url 发送给其他用户，然后他们可以通过此 URL 下载文件。

这是我上传文件的代码:

+ (void)uploadBlob:(NSData *)blob fileName:(NSString *)fileName type:(NSString *)type {
    if ([self private_checkCloudForbidden]) {
        return;
    }

    if (CHOSEN_SERVER_DATABASE == ServersQuickBlox) {
        if ([Format isThumbnailWithBlobFileName:fileName]) {
            type = @"image";
        }

        NSString *qbContentType = @"";
        if ([type isEqualToString:@"image"]) {
            qbContentType = @"image/jpg";
        }

        [QBContent TUploadFile:blob fileName:fileName contentType:qbContentType isPublic:YES delegate:[CloudDelegate sharedInstance]];


    }

    else if (CHOSEN_SERVER_DATABASE == ServersParse) {

        PFFile *file = [PFFile fileWithName:fileName data:blob];

        [file saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
            if (error){
                NSLog(@"Error: %@", [[error userInfo] objectForKey:@"error"]);
            } else {

                [CloudHandler didUploadBlobWithFileName:file.name blobID:file.url];

            }
        }];

    }
}

在 CloudHandler didUploadBlobWithFileName 方法中，我会将文件的 url 保存为 blobID。以下是我在使用 QuickBlox 时如何通过 blobID/url 下载文件:

+ (void)downloadWithBlobId: (NSString *)blobID {
    if ([self private_checkCloudForbidden]) {
        return;
    }


    if (CHOSEN_SERVER_DATABASE == ServersQuickBlox) {


        [QBContent TDownloadFileWithBlobID:blobID.integerValue delegate:[CloudDelegate sharedInstance]];

    }

    else if (CHOSEN_SERVER_DATABASE == ServersParse) {

        //TODO: HOW TO DOWNLOAD FILES?

    }

}

我没有找到通过 URL 下载文件的 API。 (如果 parse 确实提供了无用的 url 或 blobID，这有点奇怪

编辑:

我不使用"file"类型属性的原因:

1. I can't store 'file' on local database. It has to be the blobID or URL. 

2. when I send a rich message, I can send along the blobID, so that the receiver does not have to fetch the object first before downloading the binary. 

Answer 1

您应该传输 PFObject 而不是 url。像这样:

PFObject *object; //the object you have
PFFile *soundFile = object[@"file"];
[soundFile getDataInBackgroundWithBlock:^(NSData *soundData, NSError *error) {
        if (!error) {
            [self saveSoundFileToDocuments:soundData fileName:object[@"fileName"]];
        }
    }
    progressBlock:^(int percentDone) {

    }];

- (void)saveSoundFileToDocuments:(NSData *)soundData fileName:(NSString *)fileName {
    NSString *docsDir;
    NSArray *dirPaths;

    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    docsDir = [dirPaths objectAtIndex:0];
    NSString *databasePath = [[NSString alloc] initWithString: [docsDir stringByAppendingPathComponent:[DataAcesss encryptText:fileName]]];
    [soundData writeToFile:databasePath atomically:YES];
}

这样您就可以下载文件并获得文件名。