Question

我正在使用解析来聊聊我的应用程序。当我上传文件时，我会保留网址，并将网址发送给其他用户，然后用户可以通过此网址下载文件。

以下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，我将文件的url保存为blobID。以下是使用QuickBlox时通过blobID / url下载文件的方法：

+ (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，那就有点奇怪了

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

您应该转移PFObject而不是网址。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拥有文件名。

Answer 2

UIKit提供的用于从URL检索数据的API是异步的，以便使UI保持响应。它使用NSURLConnectionDelegate接口。您应该实现该接口，以便异步接收数据。首先，您可以从URL初始化检索：

NSURLRequest *theRequest=[NSURLRequest requestWithURL:anUrl
                                          cachePolicy:NSURLRequestUseProtocolCachePolicy
                                      timeoutInterval:CONNECTION_TIMEOUT];
// create the connection with the request
// and start loading the data
urlConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
if (urlConnection) {
    // Create the NSMutableData to hold the received data.
    // receivedData is an instance variable declared elsewhere.
    self.receivedData = [NSMutableData data];
} else {
    // Inform the user that the connection failed.
    NSLog(@"Failed to create connection to URL: %@.", anUrl);
}

此处包含此代码的类被设置为委托，因此应将此类声明为实现命名接口：

@interface MyClass : NSObject <NSURLConnectionDelegate> {
}
// URLConnection Delegate
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
- (void)connectionDidFinishLoading:(NSURLConnection *)connection;
- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse;

我当前的实现看起来像这样：

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    // This method is called when the server has determined that it
    // has enough information to create the NSURLResponse.

    // It can be called multiple times, for example in the case of a
    // redirect, so each time we reset the data.

    // receivedData is an instance variable declared elsewhere.
    [receivedData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // Append the new data to receivedData.
    // receivedData is an instance variable declared elsewhere.
    [receivedData appendData:data];
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    // Do error handling here
    NSLog(@"Connection failed! Error - %@ %@",
          [error localizedDescription],
          [[error userInfo] objectForKey:NSURLErrorFailingURLStringErrorKey]);
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"Succeeded! Received %d bytes of data",[receivedData length]);
    // Now process the received data accumulated in receivedData.
}

-(NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse
{
    return cachedResponse;
}

这应该让你去。

Answer 3

PFFile对象不包含下载方法，因为它内置了iOS SDK的功能。或者您可以使用AFNetworking作为替代方案。我认为下载文件最简单的方法是使用NSData的同步构造函数和GCD：

dispatch_async(dispatch_get_global_queue(0), ^(){

   NSData* data = [NSData dataWithContentsOfURL:[NSURL URLWithString:file.url]];

   dispath_async(dispatch_get_main_queue(), ^(){

      // do you main UI thread stuff here
   });
});

iOS Parse如何通过URL下载文件

3 个答案: