I have single view for both uploading and downloading images and audio files. Here what I am doing
To start downloading i am using this :
NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
and this trigger its delagate methods
connection:didReceiveResponse:
connection:didReceiveData:
connectionDidFinishLoading:
and in these methods I am calculating file size, showing downloading progress through progress bar and saving files in my device.
For uploading I am doing this
[NSURLConnection connectionWithRequest:request delegate:self];
and using this connection:didSendBodyData:totalBytesWritten:totalBytesExpectedToWrite:
this delegate methods works fine upload file and also tells about bytesWritten, totalBytesWritten, totalBytesExpectedToWrite but it also calls
connection:didReceiveResponse:
connection:didReceiveData:
connectionDidFinishLoading:
and its valid because all are delegate methods.
But problem is I am using these three to handle downloading.
What is the correct way to work with NSURLConection regarding uploading and downloading data?
Reference Apple Doc
The best way for me would be to implement the delegates in dedicated classes (e.g DownloadingDelegate and UploadingDelegate) and instantiate different delegates for each connection. The download and upload process could then be handled totally independently.
Or, if the download and upload are not concurrent, it can be simpler to use a boolean as a flag and test it in your delegates functions.
For example, let say you use a boolean instance variable called downloading.
You will have for the download:
downloading = true;
NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
And the upload:
downloading = false;
[NSURLConnection connectionWithRequest:request delegate:self];
Then in your delegate:
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
if( downloading )
{
// handle the response when downloading ...
}
else
{
// when uploading
}
}
Save the pointers to the NSURLConnections and inside the delegates determine which one is used.
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
if(connection==downloaderConn) {
//handle download
}
else {
//handle upoad
}
}
You can Use AFNetworking for your task.
AFNetworking is a delightful networking library for iOS and Mac OS X. It's built on top of NSURLConnection, NSOperation, and other familiar Foundation technologies. It has a modular architecture with well-designed, feature-rich APIs that are a joy to use.
Find the SDK here
Related
I recently started to work with NSURLConnection in my project and I'm wondering whether or not the pattern I use to handle the received data is appropriate.
In case I get a 404 or another error, I do not actually want to do anything with the data, so it would be a waste to still append it to my object. Therefore I only want to create the data object once I get a 200 status.
Is it safe to assume that -connection:didReceiveResponse: is called before any of the -connection:didReceiveData: callbacks?
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[self.data appendData:data];
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response
{
if (response.statusCode == 200) {
self.data = [NSMutableData data];
}
else {
NSLog(#"Connection failed with status code %d", response.statusCode);
[self.connection cancel];
}
}
Yes
didReceiveResponse will call beforeDidReceiveData, and it is possible it get calls many time in one connection as per apple document
You should be prepared for your delegate to receive the
connection:didReceiveResponse: message multiple times for a single
connection; this can happen if the response is in multipart MIME
encoding. Each time the delegate receives the
connection:didReceiveResponse: message, it should reset any progress
indication and discard all previously received data (except in the
case of multipart responses).
Source
I've read through tons of messages saying the same thing all over again : when you use a NSURLConnection, delegate methods are not called. I understand that Apple's doc are incomplete and reference deprecated methods, which is a shame, but I can't seem to find a solution.
Code for the request is there :
// Create request
NSURL *urlObj = [NSURL URLWithString:url];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:urlObj cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:30];
[request setValue:#"gzip" forHTTPHeaderField:#"Accept-Encoding"];
if (![NSURLConnection canHandleRequest:request]) {
NSLog(#"Can't handle request...");
return;
}
// Start connection
dispatch_async(dispatch_get_main_queue(), ^{
self.connection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES]; // Edited
});
...and code for the delegate methods is here :
- (void) connection:(NSURLConnection *)_connection didReceiveResponse:(NSURLResponse *)response {
NSLog(#"Receiving response: %#, status %d", [(NSHTTPURLResponse*)response allHeaderFields], [(NSHTTPURLResponse*) response statusCode]);
self.data = [NSMutableData data];
}
- (void) connection:(NSURLConnection *)_connection didFailWithError:(NSError *)error {
NSLog(#"Connection failed: %#", error);
[self _finish];
}
- (void) connection:(NSURLConnection *)_connection didReceiveData:(NSData *)_data {
[data appendData:_data];
}
- (void)connectionDidFinishDownloading:(NSURLConnection *)_connection destinationURL:(NSURL *) destinationURL {
NSLog(#"Connection done!");
[self _finish];
}
There's not a lot of error checking here, but I've made sure of a few things :
Whatever happens, didReceiveData is never called, so I don't get any data
...but the data is transfered (I checked using tcpdump)
...and the other methods are called successfully.
If I use the NSURLConnectionDownloadDelegate instead of NSURLConnectionDataDelegate, everything works but I can't get a hold on the downloaded file (this is a known bug)
The request is not deallocated before completion by bad memory management
Nothing changes if I use a standard HTML page somewhere on the internet as my URL
The request is kicked off from the main queue
I don't want to use a third-party library, as, ultimately, these requests are to be included in a library of my own, and I'd like to minimize the dependencies. If I have to, I'll use CFNetwork directly, but it will be a huge pain in the you-know-what.
If you have any idea, it would help greatly. Thanks!
I ran into the same problem. Very annoying, but it seems that if you implement this method:
- (void)connectionDidFinishDownloading:(NSURLConnection *)connection destinationURL:(NSURL *)destinationURL
Then connection:didReceiveData: will never be called. You have to use connectionDidFinishLoading: instead... Yes, the docs say it is deprecated, but I think thats only because this method moved from NSURLConnectionDelegate into NSURLConnectionDataDelegate.
I like to use the sendAsynchronousRequest method.. there's less information during the connection, but the code is a lot cleaner.
[NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){
if (data){
//do something with data
}
else if (error)
NSLog(#"%#",error);
}];
From Apple:
By default, a connection is scheduled on the current thread in the
default mode when it is created. If you create a connection with the
initWithRequest:delegate:startImmediately: method and provide NO for
the startImmediately parameter, you can schedule the connection on a
different run loop or mode before starting it with the start method.
You can schedule a connection on multiple run loops and modes, or on
the same run loop in multiple modes.
Unless there is a reason to explicitly run it in [NSRunLoop currentRunLoop],
you can remove these two lines:
[connection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
[connection start];
or change the mode to NSDefaultRunLoopMode
NSURLConnection API says " ..delegate methods are called on the thread that started the asynchronous load operation for the associated NSURLConnection object."
Because dispatch_async will start new thread, and NSURLConnection will not pass to that other threat the call backs, so do not use dispatch_async with NSURLConnection.
You do not have to afraid about frozen user interface, NSURLConnection providing only the controls of asynchronous loads.
If you have more files to download, you can start some of connection in first turn, and later they finished, in the connectionDidFinishLoading: method you can start new connections.
int i=0;
for (RetrieveOneDocument *doc in self.documents) {
if (i<5) {
[[NSURLConnection alloc] initWithRequest:request delegate:self];
i++;
}
}
..
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
ii++;
if(ii == 5) {
[[NSURLConnection alloc] initWithRequest:request delegate:self];
ii=0;
}
}
One possible reason is that the outgoing NSURLRequest has been setup to have a -HTTPMethod of HEAD. Quite hard to do that by accident though!
I wish to fetch data for an array of URLs that return JSON data. I am trying the following code:
for (int i =0; i<numberOfDays; i++)
{
NSData *data = [NSData dataWithContentsOfURL:[wordURLs objectAtIndex:i]];
NSLog(#"%#",[wordURLs objectAtIndex: i]);
[self performSelectorOnMainThread:#selector(fetchedData:) withObject:data waitUntilDone:YES];
}
'wordURLs' are the array of URLs and in my 'fetchedData:' method, I save the returned JSON data to a plist file.
The issue is that for all number of times that the loop runs, the data is returned for only one/two particular URLs (i.e. say for the urls at indices at 1 and 3, or 1 and 2 etc). I log and see that the URLs are different for each time the 'data' variable is initialized.
What is a better way of doing this?
I have used NSJSONSerialization for parsing JSON.
There are much better ways of doing this. The problem with what you are trying to do is that it is synchronous, which means your app will have to wait for this action to be completed before it can do anything else. I definitely would recommend looking into making this into an asynchronous call by simply using NSURLConnection and NSURLRequests, and setting up delegates for them.
They are relatively simple to set up and manage and will make your app run a million times smoother.
I will post some sample code to do this a little later once I get home.
UPDATE
First, your class that is calling these connections will need to be a delegate for the connections in the interface file, so something like this.
ViewController.h
#interface ViewController: UIViewController <NSURLConnectionDelegate, NSURLConnectionDataDelegate> {
NSMutableData *pageData;
NSURLConnection *pageConnection;
}
Then you will need to create/initialize the necessary variables in you implementation
ViewController.m
-(void) viewDidLoad {
pageData = [[NSMutableData alloc] init];
NSURLRequest *pageRequest= [[NSURLRequest alloc] initWithURL:pageURL cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:4];
pageConnection = [[NSURLConnection alloc] initWithRequest:pageRequestdelegate:self];
}
Then you also need the delegate functions that will get called as the data is retrieved.
-(void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
if (connection == pageConnection) {
[pageData appendData:data];
}
}
-(void) connectionDidFinishLoading:(NSURLConnection *)connection {
if (connection == pageConnection) {
// Do whatever you need to do with the data
}
}
-(void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
if (connection == pageConnection) {
// Do something since the connection failed
}
}
Of course this example only includes one URL being loaded, but you could make it as many as you want. You will of course have to keep track of all of the necessary NSURLConnections so you know where to put the data you received, as well as what actions to take in case of a failure or the connection being completed successfully, but that is not a hard extension from what I have given.
If you see any glaring errors or something does not work, please let me know.
In my iPad application, I want to load a modal window with some data.
But those data can be retrieved from a web service call. So, I have created another class and in that class's connectionDidFinishLoading I can have the response data. As the web service call is asynchronous, I have to wait for the data to load the modal window. Can anyone help me with some example code? Should I think in different way?
Thank you all for the prompt reply.
My problem was solved using the NSNotificationCenter. This tutorial was helpful http://www.youtube.com/watch?v=WB-QCv_4ANU&feature=plcp
Either you can load modal window from connectionDidFinishLoading method. Or you can use delegates to pass data from connectionDidFinishLoading metod to the window that you are going to present. Refer this tutorial.
You start the connection this way:
NSURL *url = [NSURL URLWithString:<#your url string#>];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
myData = [[NSMutableData alloc] init];
con = [[NSURLConnection alloc] initWithRequest:request delegate:self];
And you need to implement NSURLConnectionDelegate delegate.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
//append data to your NSMutableData object
[myData appendData: data];
}
- (void)connection:(NSURLConnection *)connection
didFailWithError:(NSError *)error
{
//handle the error
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//here you can use your NSMutableData object, fill your window with the data etc.
<#your code#>
}
This is just an example. You can read more about it in NSURLConnectionDelegate Protocol Reference.
I would like to know how I can stop/abort a NSURLConnection while it is performing it load request.
The reason I would like to know is that, I am parsing an XML using NSURLConnection and sometimes the time taken to get a response is too long.
here is my code to make things clearer...
I am parsing an XML using NSXMLParser and loading the req with my soap message before I request it using NSURLConnection
conn = [[NSURLConnection alloc] initWithRequest:req delegate:self];
if (conn)
{
webData = [[NSMutableData data] retain];
}
}
The following piece of code is what is standard
-(void) connection:(NSURLConnection *) connection
didReceiveResponse:(NSURLResponse *) response
{
[webData setLength: 0];
}
-(void) connection:(NSURLConnection *) connection
didReceiveData:(NSData *) data
{
[webData appendData:data];
}
In this, sometimes the time taken for the program to get to connection didReceiveData is too long and the user would need to abort that operation.
So I would like to know if this is possible.
I know how to abort after it starts parsing by using [parser abort] but I dont know how to abort the NSURLConnection.
It would be great if someone could help me out with this.
Use [conn cancel]; to stop an ongoing download.