How to download a file and save it to the documents directory with AFNetworking?

I am using the AFNetworking library. I can't figure out how to download a file and save it to the documents directory.

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"..."]];
AFHTTPRequestOperation *operation = [[[AFHTTPRequestOperation alloc] initWithRequest:request] autorelease];

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"filename"];
operation.outputStream = [NSOutputStream outputStreamToFileAtPath:path append:NO];

[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
    NSLog(@"Successfully downloaded file to %@", path);
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
    NSLog(@"Error: %@", error);
}];

[operation start];

I'm gonna bounce off @mattt's answer and post a version for AFNetworking 2.0 using AFHTTPRequestOperationManager.

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *path = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"filename"];

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
AFHTTPRequestOperation *op = [manager GET:@"http://example.com/file/to/download" 
                               parameters:nil
    success:^(AFHTTPRequestOperation *operation, id responseObject) {
         NSLog(@"successful download to %@", path);
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
         NSLog(@"Error: %@", error);
    }];
op.outputStream = [NSOutputStream outputStreamToFileAtPath:path append:NO];

I'm talking about AFNetworking 2.0

[AFHTTPRequestOperationManager manager] creates manager object with default AFJSONResponseSerializer, and it performs content types restriction. Take a look at this

- (BOOL)validateResponse:(NSHTTPURLResponse *)response
                    data:(NSData *)data
                   error:(NSError * __autoreleasing *)error

So we need to create a none response serializer and use AFHTTPRequestOperationManager as normal.

Here is the AFNoneResponseSerializer

@interface AFNoneResponseSerializer : AFHTTPResponseSerializer

+ (instancetype)serializer;

@end

@implementation AFNoneResponseSerializer

#pragma mark - Initialization
+ (instancetype)serializer
{
    return [[self alloc] init];
}

- (instancetype)init
{
    self = [super init];

    return self;
}

#pragma mark - AFURLResponseSerializer
- (id)responseObjectForResponse:(NSURLResponse *)response
                           data:(NSData *)data
                          error:(NSError *__autoreleasing *)error

{
    return data;
}

@end

Usage

self.manager = [AFHTTPRequestOperationManager manager];
self.manager.responseSerializer = [AFNoneResponseSerializer serializer];

[self.manager GET:@"https://sites.google.com/site/iphonesdktutorials/xml/Books.xml"
           parameters:parameters
              success:^(AFHTTPRequestOperation *operation, id responseObject)
    {
        if (success) {
            success(responseObject);
        }
    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
        if (failure) {
            failure(error);
        }
    }];

so that we can get the whole file without any serialization

Documentation page has example with section 'Creating a Download Task':

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

NSURL *URL = [NSURL URLWithString:@"http://example.com/download.zip"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];

NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:nil destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
    NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
    return [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]];
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
    NSLog(@"File downloaded to: %@", filePath);
}];
[downloadTask resume];

NB! Code work with iOS 7+ (tested with AFNetworking 2.5.1)

From AFNetworking docs. Save to loaded file to your documents. AFNetworking 3.0

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

NSURL *URL = [NSURL URLWithString:@"http://example.com/download.zip"];
NSURLRequest *request = [NSURLRequest requestWithURL:URL];

NSURLSessionDownloadTask *downloadTask = [manager downloadTaskWithRequest:request progress:nil destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
    NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
    return [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]];
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
    NSLog(@"File downloaded to: %@", filePath);
}];
[downloadTask resume];

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];

manager.responseSerializer = [AFCompoundResponseSerializer serializer];

manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"application/octet-stream"];

AFHTTPRequestOperation *operation = [manager GET:url   parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
    if (responseObject) {
        // your code here
    } else {
        // your code here
    }
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {

}];

[operation start];

// manager.responseSerializer.acceptableContentTypes = [NSSet setWithObject: @"application/octet-stream"]; can vary depending on what you expect

Yes, it is better to use AFNetworking 2.0 way with AFHTTPRequestOperationManager. With old way my file did download but for some reason didn't update in file system.

Appending to swilliam's answer, to show download progress, in AFNetworking 2.0 you do similarly - just set download progress block after setting output stream.

__weak SettingsTableViewController *weakSelf = self;

operation.outputStream = [NSOutputStream outputStreamToFileAtPath:newFilePath append:NO];

[operation setDownloadProgressBlock:^(NSUInteger bytesWritten, long long totalBytesWritten, long long totalBytesExpectedToRead) {
    
    float progress = totalBytesWritten / (float)totalBytesExpectedToRead;
    
    NSString *progressMessage = [NSString stringWithFormat:@"%@ \n %.2f %% \n %@ / %@", @"Downloading ...", progress * 100, [weakSelf fileSizeStringWithSize:totalBytesWritten], [weakSelf fileSizeStringWithSize:totalBytesExpectedToRead]];
    
    [SVProgressHUD showProgress:progress status:progressMessage];
}];

This is my method to create bytes string:

- (NSString *)fileSizeStringWithSize:(long long)size
{
    NSString *sizeString;
    CGFloat f;
    
    if (size < 1024) {
        sizeString = [NSString stringWithFormat:@"%d %@", (int)size, @"bytes"];
    }
    else if ((size >= 1024)&&(size < (1024*1024))) {
        f = size / 1024.0f;
        sizeString = [NSString stringWithFormat:@"%.0f %@", f, @"Kb"];
    }
    else if (size >= (1024*1024)) {
        f = size / (1024.0f*1024.0f);
        sizeString = [NSString stringWithFormat:@"%.0f %@", f, @"Mb"];
    }
    
    return sizeString;
}

In addition to the previous answers, with AFNetworking 2.5.0 and iOS7/8 I have found that that the extra step of opening the output stream is also needed to prevent the app from hanging (and eventually crashing from lack of memory).

operation.outputStream = [NSOutputStream outputStreamToFileAtPath:dest
                                                          append:NO];
[operation.outputStream open];
[operation start];