Hey guys I have done lots of work with ASIHTTPRequest so far and use it several times in my ios application, however in one area of my app where I have added another asihttprequest method its not working properly.
First of all it must be said that the reason I'm trying to spread the load of downloading and parsing the data.. If I do this on the subview it takes a good 2-3 second to go through the second xml sheet and get all of the related values out.. where as If I do it on this mainview where people are not seeing anything load etc then when the go back to the subview it should look almost instant. I don't know how correct this is but I figure its a okay thing to do to make the app feel abit snappier.
So I am setting it the asihttprequest methods identically as the other ones that work minus caching.
What happens is I select a table cell from the main view that loads the second view and parses a bunch of info to the tableview. the User then selects a value which is passed back to the main view and displayed.
I then parse another lot of xml data checking the selected valueID against everything in the second xml sheet. so that when the user selects the second cell I pass all the data that was just parsed over to the second view to make it look as though its loaded alot faster.
Heres a flow chart of that will explain what I'm trying to do abit better
This is what the parser code looks like in the main view which is the one thats working in the emulator but not on the iphone.
This is my protocol that I call from the subview and pass all the values I need to over and fire off the request to the mainviews ASIHTTPRequest.
- (void) setManufactureSearchFields:(NSArray *)arrayValues withIndexPath:(NSIndexPath *)myIndexPath
{
manufactureSearchObjectString = [[arrayValues valueForKey:#"MANUFACTURER"] objectAtIndex:0];
manufactureIdString = [[arrayValues valueForKey:#"MANUID"] objectAtIndex:0]; //Restricts Models dataset
manufactureResultIndexPath = myIndexPath;
[self.tableView reloadData]; //reloads the tabels so you can see the value in the tableViewCell.
//need some sort of if statment here so that if the back button is pressed modelSearchObjectString is not changed..
if (oldManufactureSearchObjectString != manufactureSearchObjectString) {
modelResultIndexPath = NULL;
modelSearchObjectString = #"empty";
oldManufactureSearchObjectString = [[NSString alloc] initWithFormat:manufactureSearchObjectString];
}
//These two lines below are what execute ASIHTTPRequest and set up my parser etc
dataSetToParse = #"ICMod"; // This sets the if statment inside parserDidEndDocument
[self setRequestString:#"ICMod.xml"]; //Sets the urlstring for XML inside setRequestString
}
This then fires the ASIHTTPRequest delegate methods.
- (IBAction)setRequestString:(NSString *)string
{
//Set database address
//NSMutableString *databaseURL = [[NSMutableString alloc] initWithString:#"http://127.0.0.1:8888/codeData/"]; // imac development
NSMutableString *databaseURL = [[NSMutableString alloc] initWithString:#"http://127.0.0.1:8888/codeData/"]; // iphone development
//PHP file name is being set from the parent view
[databaseURL appendString:string];
NSLog(#"%#", databaseURL);
//call ASIHTTP delegates (Used to connect to database)
NSURL *url = [NSURL URLWithString:databaseURL];
//This sets up all other request
ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
[request setDelegate:self];
[request startAsynchronous];
}
When I run this through debug with break points while testing on the iphone this is where the app falls over.. but On the emulator it has no problems.
This next method never gets called when testing on the iphone but workds sweet on the emulator.
- (void)requestFinished:(ASIHTTPRequest *)request
{
responseString = [request responseString]; //Pass requested text from server over to NSString
capturedResponseData = [responseString dataUsingEncoding:NSUTF8StringEncoding];
[self startTheParsingProcess:capturedResponseData];
}
This is the only other delegate that is fired when testing on the iphone, sends me an alret saying the connection has timed out.
- (void)requestFailed:(ASIHTTPRequest *)request
{
NSError *error = [request error];
NSLog(#"%#", error);
UIAlertView *errorAlert = [[UIAlertView alloc] initWithTitle:#"Error!" message:#"A connection failure occurred." delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[errorAlert show];
}
I don't think you need to see all the parser delegates as I don't think they are the issue as this is where the app falls over...
here is what gets printed to the log...
2011-11-29 14:38:08.348 code[1641:707] http://000.000.000.000:0000/codeData/second.xml
2011-11-29 14:38:18.470 code[1641:707] Error Domain=ASIHTTPRequestErrorDomain Code=2 "The request timed out" UserInfo=0x1e83a0 {NSLocalizedDescription=The request timed out}
If you need more of my code let me know.. but I'm at abit of a loss here as like I say there is no difference to how Im doing this ASIHTTPRequest to other views other than I'm initializing it from the protocol that I'm setting up from the second view.. maybe I should set the values before I reload the table or something... I'm not sure though hopefully someone can help me out with this one and spot the issue I cannot see.
Can you view 'http://127.0.0.1:8888/codeData/' with Safari on the iPhone? Chances are that server isn't available from whatever networks the iPhone is connected to.
If your iMac is using DCHP it is possible that the address has changed since you originally set the value.
Are you sure you have the case correct on the URL? The simulator is much more forgiving on case-sensitivity than the actual device.
Do not fly blind but use an HTTP Proxy like Charles for making sure your requests are actually fired and result into what you expect.
Related
I am currently designing an iOS 5 iPhone app that will use a .NET RESTful Web Service to provide data updates. When the application is initially installed, it will connect to the WS to download all the data in a JSON format. Thereafter, it will only perform updates. The WS provides a POST method for each table as GetAllTableRecords() and GetLastUpdatedTableRecords().
I am using iOS 5 and I've got the NSURLConnection and JSON serialization/deserialization working correctly with native libraries. Each WS POST method call is currently residing in its own Obj-C class with all of the delegate methods. Additionally, each class handles the local datastore inserts and updates.
Each NSURLConnection is asynchronous and all of the WS calls are driven off of button events from view controllers.
My questions are:
Is this the right setup in terms of code encapsulation and reuse?
How do I handle making multiple WS calls while keeping the user
informed via the UI?
Currently there are two tables to download. This means the app will call the WS twice to get the initial data and twice again during each refresh. I know that since each NSURLConnection is asynchronous, the connection will make the request but the UI will continue on while the delegate handles the data download. I've done some research into GCD and NSOperation/Queue but I don't know enough about either one to code a solution or know if that's even a correct solution.
Any insight would be most helpful!
Edit #1: What about providing real time updates back to the UI? The Mint app does something similar when updating transactions and accounts. They have a little status bar that pops up at the bottom while requests are made.
Edit #2: Ok, I believe I've made some progress. We are using Story Boards and the entry point is the Login View/Controller. When the login button is clicked, a NSURLConnection is made to the webservice. If the response status code is 200 in connectionDidFinishLoading:(NSURLConnection *)connection, a segue is performed to go the Data Sync View. The purpose of this view is to either initialize or update the database while providing feedback to the user. Either updating or initializing requires two additional web service calls.
Here's my DataSyncView.m:
#synthesize pvStatus, lbStatus;
// pvStatus = progress indicator
// lbStatus = label
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view from its nib.
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
// e.g. self.myOutlet = nil;
}
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[self StartDataSync];
}
- (void)StartDataSync
{
[lbStatus setText:#"Syncing data..."];
[pvStatus setProgress:0.0f];
// TODO: Determine if database is popuplated
[self PerformInitialSync];
// Next screen
[self performSegueWithIdentifier:#"SegueFromSync" sender:self];
}
// Populates data store will data from web service
- (void)PerformInitialSync
{
// Kicks off a series of synchronous requests
[self DownloadAllEmployeeDataA];
}
- (void)DownloadAllDataA
{
// Dictonary holds POST values
NSMutableDictionary *reqDic = [NSMutableDictionary dictionary];
// Populate POST key/value pairs
[reqDic setObject:passWord forKey:#"Password"];
[reqDic setObject:userName forKey:#"UserName"];
NSError *error = nil;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:reqDic options:NSJSONWritingPrettyPrinted error:&error];
// Convert dictionary to JSON
NSString *requestJSON = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
// Declare Webservice URL, request, and return data
NSURL *url = [[NSURL alloc] initWithString:#"http://wsurl/getalla"];
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
NSData *postData = [NSData dataWithBytes:[requestJSON UTF8String] length:[requestJSON length]];
// Build the request
[request setHTTPMethod:#"POST"];
[request setValue:[NSString stringWithFormat:#"%d", [postData length]] forHTTPHeaderField:#"Content-Length"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:postData];
[request setCachePolicy:NSURLRequestUseProtocolCachePolicy];
[request setTimeoutInterval:60.0];
NSURLResponse *response;
[lbStatus setText:#"Downloading employee data..."];
[pvStatus setProgress:0.1f];
// Make the response
NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
// If return data received
if(returnData)
{
// Get the response and check the code
NSHTTPURLResponse* httpResponse = (NSHTTPURLResponse*)response;
int code = [httpResponse statusCode];
// Check to make sure successful code
if (code == 200)
{
// Convert JSON objects to Core Data Entity
// Update UIProgressView and Label
// Call next WS call
[self DownloadAllEmployeeDataA];
}
}
}
- (void)DownloadAllDataB
{
// Same code as above but with different URL and entity
}
My problem that I am having is this: The UIProgressView and Label are not updating as the calls are being made. As I stated before, I don't even know if this is the best way to make these calls. It doesn't appear that I'm blocking the main thread but I could be wrong. Again, I'll pose the question: what is the best way to make multiple url calls while keeping the UI updated on the progress? Thanks!!!
// Make the response
NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
In your question you said you made asynchronous load of url request. But in the above line of code you are making a synchronous request ?
Is this the right setup in terms of code encapsulation and reuse?
Looking at your code you are not adhering to MVC. Your View
Controller shouldn't manage loading URL connections. You can create a
class that does that and using delegates inform the view controller
whether data is downloaded or failed to download,etc.
How do I handle making multiple WS calls while keeping the user informed via the UI?
If you want to make concurrent URL Connections then use NSOperation
and NSOperationQueue. Try avoiding GCD ( Refer to WWDC 2010 Session
208 ).
My problem that I am having is this: The UIProgressView and Label are not updating as the calls are being made.
You are making a Synchronous URL request on main thread. As per your
code UIProgressView shouldn't update.
Refer URL Loading System Programming Guide
Another comment I have is your method names, start method name with small letter. Rest of it looks fine. Coding Guidelines for Cocoa
First of all the questions are failry simiple.. if you just want to see what they are skip to the bottom of this post and you will see them in bold.. for more detail then you can read the rest of this post...
I am just trying to iron out my NSURLConnection so that its working smoothly and I understand this properly. There is a profound lack of example/tutorials for Asynchronous connections on the internet or not any that I can find that explaine what is going on with any level of depth other than getting the connection up and running which after working on it seems pretty simple. Hopefully this question can full the void that I feel is out there for other users.
So, in my .h file i have imported the foundations headers and declared the methods required for the received or lack of received data (errors etc).
.h
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h> //add foundations
//.. other headers can be imported here
#interface MyViewController: UITableViewController {
//Im not setting any delegates to access the methods because Is all happening in the same
//place so I just use the key word 'self' when accessing the methods declared below
//I'm not sure if this is the best thing to do but I wasn't able to get my head around declaring the delegate or how it would help me with the way I have set up my request etc.
}
- (IBAction)setRequestString:(NSString *)string; //this method sets the request and connection methods
//these methods receive the response from my async nsurlconnection
- (void)receivedData:(NSData *)data;
- (void)emptyReply;
- (void)timedOut;
- (void)downloadError:(NSError *)error;
So thats my header file.. pretty simple not much explaining needed.
.m
//call setRequestString from some other method attached to a button click or something
[self setRequestString:#"rss.xml"];
//..
- (IBAction)setRequestString:(NSString *)string
{
//Set database address
NSMutableString *databaseURL = [[NSMutableString alloc] initWithString:#"http:www.comicbookresources/feeds/"]; // address not real jsut example
//append the string coming in to the end of the databaseURL
[databaseURL appendString:string];
//prepare NSURL with newly created string
NSURL *url = [NSURL URLWithString:databaseURL];
//AsynchronousRequest to grab the data
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if ([data length] > 0 && error == nil){
[self receivedData:data];
}else if ([data length] == 0 && error == nil){
[self emptyReply];
}else if (error != nil && error.code == NSURLErrorTimedOut){ //used this NSURLErrorTimedOut from foundation error responses
[self timedOut];
}else if (error != nil){
[self downloadError:error];
}
}];
}
now set up the methods that were initialized in the .h file and called in the if statement above
- (void)receivedData:(NSData *)data
{
NSString* newStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"%#", newStr); //logs recived data
//now you can see what data is coming in on your log
//do what you want with your data here (i.e. start parsing methods
}
- (void)emptyReply
{
//not sure what to do here yet?
}
- (void)timedOut
{
//also not sure what to do here yet?
}
- (void)downloadError:(NSError *)error
{
NSLog(#"%#", error);
UIAlertView *errorAlert = [[UIAlertView alloc] initWithTitle:#"Error!" message:#"A connection failure occurred." delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[errorAlert show];
}
Cool so that pretty much the basics of what I have done right there.. now the questions I have are as follows.
Question one:
Where I call NSURLConnection like so
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
What is happening here what is the ^ for is that executing that whole block (including the if statements) on a different thread or something? because it looks alot like grand central dispatch formatting but slightly different.
Question two:
what should I be doing inside emptyReply & timedOut methods?
Question three:
How would I incorporate caching into this? I would like to cache the responses I get back from different requests. i.e. with my setRequestString you will see there is a string input parameter, so i can request different rss feeds with the same method.. I need to figure out how to cache these responses into individual caches.. but im not sure where to start with it.
Finally
If you have made it this far, thank you very much for reading my question. Hopefully with your responses we can get a pretty nice solution going here.. that other people can use for themselves and pick and choose the bits and peices they need that works for there own solution..
Anyway thank you very much for reading and I look forward to your replies.. even if they are just refrences to tutorials or examples you think might help me.. anything is good I just want to fully understand whats going on and whats a good solution.
Read about blocks in Apple documentation. Its new. Or you can read here
You can show errors such as request timed out etc. You don't really have to handle them separately than the error one unless you have special logic.
Try this for caching
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:TIMEOUT_INTERVAL];
A brief over view of what I am trying to do.
I am using the tableView:didSelectRowAtIndexPath: method inside my UITableViewController subclass which is catching a row selection from that view like so...
//..... inside tableView:didSelectRowAtIndexPath:
if (indexPath.section == 0) {
//--- Get the subview ready for use
VehicleSearchResponseTableViewController *vehicleSearchResponseTableViewController = [[VehicleSearchResponseTableViewController alloc] initWithNibName:#"VehicleSearchResponseTableViewController" bundle:nil];
// ...
//--- Sets the back button for the new view that loads
self.navigationItem.backBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:#"Back" style: UIBarButtonItemStyleBordered target:nil action:nil] autorelease];
// Pass the selected object to the new view controller.
[self.navigationController pushViewController:vehicleSearchResponseTableViewController animated:YES];
if(indexPath.row == 0) {
vehicleSearchResponseTableViewController.title = #"Mans";
EngineRequests *engineRequest = [[EngineRequests alloc] init];
[engineRequest getMans];
[engineRequest release];
}
if(indexPath.row == 1) {
//.... etc etc
As you can see in this method I set up a few things, pushing the new view onto the viewstack and changing the back buttons text, then I go into catching the different rows and then initiating a method in a subclass of nsobject where I want to have all my connection/request stuff going on.
Inside my NSObject I have several different methods for the different cells that you can select on the UITableViewController, basicly they specify different strings that will then initialize my ASIHTTPRequest wrapper to make a connection to the php script and catch all the data that will come back from the database.. NSObject looks like this.
//.... NSObject.m
- (IBAction) getMans
{
NSString *mansString = [[NSString alloc] initWithString:#"mans.php"];
[self grabURLInBackground:mansString];
[manusString release];
}
//....cont....
//--- Connect to server and send request ---------------->>
- (IBAction)grabURLInBackground:(NSString *)setUrlString
{
NSString *startURL = [NSString stringWithFormat:#"http://127.0.0.1:8888/CodeTest/%#", setUrlString];
NSURL *url = [NSURL URLWithString:startURL];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request startAsynchronous];
}
- (void)requestFinished:(ASIHTTPRequest *)request
{
NSString *responseString = [request responseString]; //Pass request text from server over to NSString
NSData *responseData = [responseString dataUsingEncoding:NSUTF8StringEncoding]; //Create NSData object for Parser Delegate and load with responseString
NSLog(#"stuff %#",responseData);
}
- (void)requestFailed:(ASIHTTPRequest *)request
{
NSError *error = [request error];
NSLog(#"%#", error);
}
From here I would like to pass the data I am getting from the requestFinished method back over to the newly pushed UITableView.. However I have an error before I am able to get this far that I need to solve... if I run the simulator and click back and forth between the views (the main UITableViewController with the cells and then the newly popped view where I want to put the data) the application falls over and pops up an error in main.m Thread 1: program receive signal EXC_BAD_ACCESS.. I just don;t know whats causing because from what I can tell my code is not so bad.
Also when I debug my application I notice that once grabURLInBackground method has finished it bounces out back to the getMans method then goes back over to the UITableViewController and continues through the if statements, completely neglecting the requestFinished and requestFailed methods, and I just cannot figure out why.
I guess I am not sure if I am calling the methods and functions I need to use in the right places so if you have any suggestions or answers on how I can improve or if you know where my error is coming form that would be greatly appreciated.
There's a few issues with the code above but I'd guess that your bad access exception is due to the handling of your EngineRequests and use of AsiHttpRequest.
The code here
EngineRequests *engineRequest = [[EngineRequests alloc] init];
[engineRequest getMans];
[engineRequest release];
effectively creates an object then deallocates as soon as getMans has finished running.
Then inside the engineRequest object this code
[request setDelegate:self];
[request startAsynchronous];
requests that AsiHttpRequest notify the almost certainly released object once the request has completed.
There may be other issues at work here but I'd start by restructuring to try to keep this object around until at least after it's received the response from AsiHttpRequest.
Hard to tell from the brief overview, but generally when you bad_access and end up in the main application method, it's usually because you autoreleased something, then released it, and it craps out when the autorelease pool is drained. Might want to turn on NSZombiesEnabled and look for memory problems.
Who does receive your request?
The sender (and receiver) object is engineRequest.
But you release Engine Request in that very moment after you issued the async request (by mens of the getMans Method.
I would suggest that you
1. move the code
vehicleSearchResponseTableViewController.title = #"Mans";
EngineRequests *engineRequest = [[EngineRequests alloc] init];
[engineRequest getMans];
[engineRequest release];
from your UITableViewController's didSelectRowAtIndexPath method to your vehicleSearchResponseTableViewController's viewDidLoad method.
2. to retain your EngineRequests object and keep it in some instance variable within vehicleSearchResponseTableViewControllerand do not release it before the request is completely processed, either successfully or in error.
I have a strange issue, when it comes to parsing XML with NSXMLParser on the iPhone. When starting the app, I want to preload 4 table-views, that are populated by RSS-Feeds in the background.
When I init the table-views one-by-one, than loading, parsing and displaying all works like a charm. But when I try to init all view at once (at the same time), than it seems, that the XML-parser-instances are disturbing each other. Somehow data from one XML-Feed are "broadcasted" into other xml-parser instances, where they do not belong. Example: there is a "teammember" item, with "This is my name". When this bug occurs, there is a string from another xml-feed added, i.e. resulting in: "This is my name58", where 58 is the chart-position of something from the other view. "58" seems to miss then on the other instance.
It looks to me, that this bug occurs because of the NSXMLParser-delegate method:
- (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string {
if (!currentStringValue) {
currentStringValue = [[NSMutableString alloc] initWithCapacity:50];
}
[currentStringValue appendString:string];
}
In this case "by coincidence" bytes are appended to strings, where they do not belong to.
The strange thing is, that every instance of NSXMLParser is unique, got its own unique delegates, that are attached to their own ViewController. Every parsing-requests spawns it own background-task, with its own (also also unique named) Autorelease-pool.
I am calling the NSXMLParser like this in the ViewController:
// prepare XML saving and parsing
currentStringValue = [[[NSMutableString alloc] initWithCapacity:50] retain];
charts = [[NSMutableArray alloc] init];
NSURL *url = [[NSURL alloc] initWithString:#"http://(SOME XML URL)"];
xmlParser = [[[NSXMLParser alloc] initWithContentsOfURL:url] retain];
//Set delegate
[xmlParser setDelegate:self];
//loading indicator
progressWheel = [[[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(150.0,170.0,20.0,20.0)] autorelease];
progressWheel.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray;
[self.view addSubview:progressWheel];
[progressWheel startAnimating];
// start loading and parsing the xml-feed in the background
//[self performSelectorInBackground:#selector(parse:) withObject:xmlParser]; -> I also tried this
[NSThread detachNewThreadSelector:#selector(parse:) toTarget:self withObject:xmlParser];
And this is one of the background-tasks, parsing the feed:
-(void)parse:(NSXMLParser*)myParser {
NSAutoreleasePool *schedulePool = [[NSAutoreleasePool alloc] init];
BOOL success = [myParser parse];
if(success) {
NSLog(#"No Errors. xmlParser got: %#", myParser);
(POST-PROCESSING DETAILS OF THE DATA RETURNED)
[self.tableView reloadData];
} else {
NSLog(#"Couldn't initalize XMLparser");
}
[progressWheel stopAnimating];
[schedulePool drain];
[myParser release];
}
What could cause this issue? Am I calling the background-task in the right way? Why is this bug approaching, since every XML-Parser got its own, unique instance?
You should not be updating UI elements (like progressWheel) from inside a background thread. UI updates should be done on the main thread.
Use -performSelectorOnMainThread:withObject:waitUntilDone: to update UI elements from within a background thread.
I've released an open source RSS/Atom Parser for iPhone and it makes reading and parsing web feeds extremely easy.
You can set it to download the data asynchronously, or you could run it in a background thread synchronously to collect the feed data.
Hope this helps!
I'm trying to download several images in response to a single http request. On the server side (java) I'm using oreilly multipart response and I'm getting my datas in my iPhone Simulator in didReceiveData (approximately one call for each image) after a call to didReceiveResponse (approximately one call for each image as well) in my delegate.
The problem is this approximately... Has anyone ever managed to handle correctly multipart/x-mixed-re with iPhone SDK ? If yes what is the best strategy here ? Should I play with the expected length ? on server side ? on client side ? should I wait until I've received everything... mmmh that doesn't even seen enough as the calls to didReceiveData happens in a random order (I'm asking picture1,picture2 and I'm sometimes receiving picture2,picture1 even though the order is respected on server side !). Should i temporize between pictures on server side ?
Or should I drop multipart/x-mixed-replace ? what would be the easiest then ?
That's a lot of questions but I'm really stuck here ! Thanks for you help !
I'm not sure what your final use for the images is, but the intended purpose of the multipart/x-midex-replace content type is for each received part to completely replace the previously received responses. Think of it like frames of a video; only one picture is displayed at a time and the previous ones are discarded.
Temporizing is almost never a foolproof solution. Especially on the iPhone you're going to encounter an unimaginable variety of network situations and relying on a magic number delay between frames will probably still fail some of the time.
Since you have control of the server, I'd recommend dropping the multipart. Make sure when you are sending multiple requests to the server that you don't block the main thread of your iPhone app. Use NSOperations or an alternative HTTP library (like ASIHTTPRequest) to make your image fetch operations asynchronous.
I did that successfully using this code. The important thing is to create 2 buffers to receive your data. If you use only one you will have some double access problems (stream access and jpg CODEC access) and corrupted JPG data.
Do not hesitate to ask me for more details.
- (IBAction)startDowload:(id)sender {
NSURL *url = [NSURL URLWithString:#"http://210.236.173.198/axis-cgi/mjpg/video.cgi?resolution=320x240&fps=5"];
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
[req setHTTPMethod:#"GET"];
/*
I create 2 NSMutableData buffers. This points is very important.
I swap them each frame.
*/
receivedData = [[NSMutableData data] retain];
receivedData2 = [[NSMutableData data] retain];
currentData = receivedData;
urlCon = [[NSURLConnection alloc] initWithRequest:req delegate:self];
noImg = YES;
frame = 0;
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)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 declared as a method instance elsewhere
UIImage *_i;
#try
{
_i = [UIImage imageWithData:currentData];
}
#catch (NSException * e)
{
NSLog(#"%#",[e description]);
}
#finally
{
}
CGSize _s = [_i size];
[imgView setImage:_i];
[imgView setNeedsDisplay];
[[self view] setNeedsDisplay];
}
/*
Buffers swap
*/
if (currentData == receivedData)
{
currentData = receivedData2;
}
else
{
currentData = receivedData;
}
[currendData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// append the new data to the currentData (NSData buffer)
[currendData appendData:data];
}