calculating total progress of downloading multiple file with AFNetworking - ios

Question

I want to download multiple file and then display a total progress to the user.
but the problem is here I dont know how should I calculate total progress .
here is what I do:
first I get to totalBytes Expected to receive from all of the files:
for (NSURL candidateUrl in UrlsList)
{
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:candidateURL];
//setting HTTPMethod of request from GET to HEAD to download header files of requests, so we can get file size before downloaing file
[request setHTTPMethod:#"HEAD"];
getTotalImagesBytesOperation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[getTotalImagesBytesOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject)
{
//setting totalImagesBytesExpectedToRead of all images. we use it to know how many bytes we should download for all the images
totalImagesBytesExpectedToRead += [operation.response expectedContentLength];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Error: %#", error);
}];
[operationQueue addOperation:getTotalImagesBytesOperation];
}
after estimating total files size:
//downloading images
for (NSURL *imageUrl in imagesURLList) {
NSURLRequest *request = [NSURLRequest requestWithURL:imageUrl];
AFImageRequestOperation *downloadImageOperation = [AFImageRequestOperation imageRequestOperationWithRequest:request
imageProcessingBlock:nil
success: ^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
NSLog(#"success")
}
failure: ^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
NSLog(#"%#", [error localizedDescription]);
}];
[operationQueue addOperation:downloadImageOperation];
[downloadImageOperation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead)
{
**HOW TO CALCULATE TOTAL PROGRESS**
}
I don't know how to calculate total size!!
the values we have:
totalBytesOfAllTheFiles, totalBytesRead and totalBytesExpectedToRead for the current file which above method gives you, indexOfCurrentFile and countOfFiles.
be cautious setDownloadProgressBlock called hundreds a time.
does anyone have any idea? (sorry for bad formatting of code!)

Answer 1

Here is how I achieved that:
first create an NSOperationQueue:
// Add the operation to a queue
// It will start once added
//calculating images byte size
NSOperationQueue *operationQueue = [[NSOperationQueue alloc] init];
[operationQueue setMaxConcurrentOperationCount:1];
foreach (NSURL *candidateURL in urlList )
{
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:candidateURL];
//setting HTTPMethod of request from GET to HEAD to download header files of requests, so we can get file size before downloaing file
[request setHTTPMethod:#"HEAD"];
AFHTTPRequestOperation *getTotalImagesBytesOperation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[getTotalImagesBytesOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject)
{
//setting totalImagesBytesExpectedToRead of all images. we use it to know how many bytes we should download for all the images
totalImagesBytesExpectedToRead += [operation.response expectedContentLength];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"Error: %#", error);
}];
[operationQueue addOperation:getTotalImagesBytesOperation];
}
//downloading images which should be downloaded
for (NSURL *imageUrl in imagesShouldBeDownlaoded) {
NSURLRequest *request = [NSURLRequest requestWithURL:imageUrl];
AFHTTPRequestOperation *downloadFileOperation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
//we must provide file path with file name and its extension
NSString *fileName = [self getImageName:[imageUrl absoluteString]];
downloadFileOperation.outputStream = [NSOutputStream outputStreamToFileAtPath:[[ImageManager applicationDocumentsDirectory] stringByAppendingPathComponent:fileName] append:NO];
[downloadFileOperation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation , id response)
{
NSLog(#"file saved");
}failure:^(AFHTTPRequestOperation *operation, NSError *error)
{
completionBlock(NO, error);
NSLog(#"%#", [error localizedDescription]);
}];
[operationQueue addOperation:downloadFileOperation];
[downloadFileOperation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead)
{
totalBytesDownloaded += bytesRead;
//total progress from 0.0 to 1.0
progress = ((float)totalBytesDownloaded/(float)totalImagesBytesExpectedToRead);
if(progress == 1)
{
completionBlock(YES, nil);
}
progressCallback(progress);
}];
operationQueue works as a FIFO list, first calculate images byte size, then starts to download all images

Answer 2

AFNetworking3 use dispatch_group and NSProgress to achieved this:
#import <Foundation/Foundation.h>
#import <AFNetworking.h>
#interface Server : NSObject
#property (nonatomic, strong) AFHTTPSessionManager *manager;
#property (nonatomic, strong) NSProgress *progress;
- (void)downloadFilesWithUrls:(NSMutableArray <NSURL *>*)urls;
#end
#import "Server.h"
#implementation Server
- (instancetype)init
{
self = [super init];
if (self) {
_manager = [AFHTTPSessionManager manager];
_manager.requestSerializer = [AFJSONRequestSerializer serializer];
_manager.responseSerializer = [AFJSONResponseSerializer serializer];
_progress = [NSProgress progressWithTotalUnitCount:0];
[_progress addObserver:self forKeyPath:#"fractionCompleted" options:NSKeyValueObservingOptionNew context:nil];
}
return self;
}
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
NSLog(#"fractionCompleted:%lf",self.progress.fractionCompleted);
}
- (void)downloadFilesWithUrls:(NSMutableArray <NSURL *>*)urls {
//progress
dispatch_group_t group = dispatch_group_create();
_progress.totalUnitCount = urls.count;
[urls enumerateObjectsUsingBlock:^(NSURL * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
dispatch_group_enter(group);
NSURLRequest *request = [NSURLRequest requestWithURL:obj];
NSURLSessionDownloadTask *task = [self.manager downloadTaskWithRequest:request progress:^(NSProgress * _Nonnull downloadProgress) {
} destination:^NSURL * _Nonnull(NSURL * _Nonnull targetPath, NSURLResponse * _Nonnull response) {
return [[[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil] URLByAppendingPathComponent:[response suggestedFilename]];
} completionHandler:^(NSURLResponse * _Nonnull response, NSURL * _Nullable filePath, NSError * _Nullable error) {
NSLog(#"one task completion");
dispatch_group_leave(group);
}];
NSProgress *child = [self.manager downloadProgressForTask:task];
[self.progress addChild:child withPendingUnitCount:1];
[task resume];
}];
dispatch_group_notify(group, dispatch_get_main_queue(), ^{
NSLog(#"%lf", self.progress.fractionCompleted);
});
}
#end