I've looked around a lot and cant seem to find a proper answer for my problem. As of now I have a network engine and I delegate into that from each of the view controllers to perform my network activity.
For example, to get user details I have a method like this:
- (void) getUserDetailsWithUserId:(NSString*) userId
{
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#Details", kServerAddress]]];
request.HTTPMethod = #"POST";
NSString *stringData = [NSString stringWithFormat:#"%#%#", kUserId, userId];
NSData *requestBodyData = [stringData dataUsingEncoding:NSUTF8StringEncoding];
request.HTTPBody = requestBodyData;
NSURLConnection *conn = [[NSURLConnection alloc] init];
[conn setTag:kGetUserInfoConnection];
(void)[conn initWithRequest:request delegate:self];
}
And when I get the data in connectionDidFinishLoading, I receive the data in a NSDictionary and based on the tag I've set for the connection, I transfer the data to the required NSDictionary.
This is working fine. But now I require two requests going from the same view controller. So when I do this, the data is getting mixed up. Say I have a connection for search being implemented, the data from the user details may come in when I do a search. The data is not being assigned to the right NSDictionary based on the switch I'm doing inside connectionDidFinishLoading. I'm using a single delegate for the entire network engine.
I'm new to NSURLConnection, should I setup a queue or something? Please help.
EDIT
Here's the part where I receive data in the connectionDidFinishLoading:
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
if ([connection.tag integerValue] == kGetUserDetails)
networkDataSource.userData = self.jsonDetails;
if ([connection.tag integerValue] == kSearchConnection)
networkDataSource.searchData = self.jsonDetails;
}
and after this I have a switch case that calls the required delegate for the required view controller.
Anil here you need to identify for which request you got the data,
simplest way to check it is as below,
- (void)connectionDidFinishLoading:(NSURLConnection *)conn
{
// Check URL value for request, url for search and user details will be different, put if condition as per your need.
conn.currentRequest.URL
}
Try using conn.originalRequest.URL it will give original request.
You can do in many ways to accomplish your task as mentioned by others and it will solve your problem . But if you have many more connections , you need to change your approach.
You can cretae a subclass of NSOperation class. Provide all the required data, like url or any other any informmation you want to get back when task get accomplish , by passing a dictionary or data model to that class.
In Nsoperation class ovewrite 'main' method and start connection in that method ie put your all NSURRequest statements in that method. send a call back when download finish along with that info dict.
Points to be keep in mind: Create separte instance of thet operation class for evey download, and call its 'start method'.
It will look something like :
[self setDownloadOperationObj:[[DownloadFileOperation alloc] initWithData:metadataDict]];
[_downloadOperationObj setDelegate:self];
[_downloadOperationObj setSelectorForUpdateComplete:#selector(callBackForDownloadComplete)];
[_downloadOperationObj setQueuePriority:NSOperationQueuePriorityVeryHigh];
[_downloadOperationObj start];
metaDict will contain your user info.
In DownloadFileOperation class you will overwrite 'main' method like :
- (void)main {
// a lengthy operation
#autoreleasepool
{
if(self.isCancelled)
return;
// //You url connection code
}
}
You can add that operation to a NSOperationQueue if you want. You just need to add the operation to NSOperationQueue and it will call its start method.
Declare two NSURLConnection variables in the .h file.
NSURLConnection *conn1;
NSURLConnection *conn2;
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
if(connection == conn1){
}
else if(connection == conn2){
}
}
Related
I am using objective-C to write an app which needs to dispatch 100 web request and the response will be handled in the call back. My question is, how can I execute web req0, wait for call back, then execute web req1 and so on?
Thanks for any tips and help.
NSURL *imageURL = [[contact photoLink] URL];
GDataServiceGoogleContact *service = [self contactService];
// requestForURL:ETag:httpMethod: sets the user agent header of the
// request and, when using ClientLogin, adds the authorization header
NSMutableURLRequest *request = [service requestForURL:imageURL
ETag: nil
httpMethod:nil];
[request setValue:#"image/*" forHTTPHeaderField:#"Accept"];
GTMHTTPFetcher *fetcher = [GTMHTTPFetcher fetcherWithRequest:request];
fetcher.retryEnabled = YES;
fetcher.maxRetryInterval = 0.3;
fetcher.minRetryInterval = 0.3;
[fetcher setAuthorizer:[service authorizer]];
[fetcher beginFetchWithDelegate:self
didFinishSelector:#selector(imageFetcher:finishedWithData:error:)];
}
- (void)imageFetcher:(GTMHTTPFetcher *)fetcher finishedWithData:(NSData *)data error:(NSError *)error {
if (error == nil) {
// got the data; display it in the image view. Because this is sample
// code, we won't be rigorous about verifying that the selected contact hasn't
// changed between when the fetch began and now.
// NSImage *image = [[[NSImage alloc] initWithData:data] autorelease];
// [mContactImageView setImage:image];
NSLog(#"successfully fetched the data");
} else {
NSLog(#"imageFetcher:%# failedWithError:%#", fetcher, error);
}
}
You can't simply call this code in a loop as GTMHTTPFetcher works asynchronously so the loop, as you see, will iterate and start all instances without any delay.
A simple option is to put all of the contacts into a mutable array, take the first contact from the array (remove it from the array) and start the first fetcher. Then, in the finishedWithData callback, check if the array contains anything, if it does remove the first item and start a fetch with it. In this way the fetches will run serially one after the other.
A better but more complex solution would be to create an asynchronous NSOperation (there are various guides on the web) which starts a fetch and waits for the callback before completing. The benefit of this approach is that you can create all of your operations and add them to an operation queue, then you can set the max concurrent count and run the queue - so you can run multiple fetch instances at the same time. You can also suspend the queue or cancel the operations if you need to.
I have a lot of classes which are sending requests and finally it all comes to SplitViewController. In the SplitUIviewclass I have to long poll and write the data in a table view. The long polling is done in the background thread, so I have declared a variable in app delegate, but when it comes to that it is nil. And the problem is whenever I try to access the NSMutablearray through the appdelegate, its coming as nil and the array is being released. My code for long polling is
- (void) longPoll {
#autoreleasePool
{
//compose the request
NSError* error = nil;
NSURLResponse* response = nil;
NSURL* requestUrl = [NSURL URLWithString:#"http://www.example.com/pollUrl"];
NSURLRequest* request = [NSURLRequest requestWithURL:requestUrl];
//send the request (will block until a response comes back)
NSData* responseData = [NSURLConnection sendSynchronousRequest:request
returningResponse:&response error:&error];
//pass the response on to the handler (can also check for errors here, if you want)
[self performSelectorOnMainThread:#selector(dataReceived:)
withObject:responseData waitUntilDone:YES];
}
//send the next poll request
[self performSelectorInBackground:#selector(longPoll) withObject: nil];
}
- (void) startPoll {
[self performSelectorInBackground:#selector(longPoll) withObject: nil];
}
- (void) dataReceived: (NSData*) theData {
//i write data received here to app delegate table
}
If I call any other method in my SplitView class from data received, I'm losing control, also I cannot print my app delegate values in data received or the variables being released, I cannot call reload table or any other method from here.
Cant you set your properties in your ViewControllers as strong/retain like so
property (strong,retain) NSMutableArray *myData;
BTW, I learned a moment ago that it is bad practise to use your AppDelegate as a storage place for global containers. The ApplicationDelegate is a place for application delegate methods and for the initial setup of the foundation of your app; such as setting up the navigationController.
So consider storing your data in the appropriate place, perhaps core data or something else.
hi I have an UITableView. It loads numberof data from a web service. What I want to load this tableview 10 by 10.Initially it loads first 10 items. When user scroll to the end of the UITableView it should load next 10 of records from the server. so in my scrollviewDidEndDeclarating delegate I put like this
`
if (scrollView.tag==24) {
[self performSelector:#selector(loadingalbumsongs:) withObject:nil afterDelay:0.1];
}`
but the problem is when I stop the scroll it is getting stuck untill load the table view. Can anybody give me a solution for this
Thanks
Try NSURLCONNECTION that will help you to call asynchronous webservice
A NSURLConnection object is used to perform the execution of a web service using HTTP.
When using NSURLConnection, requests are made in asynchronous form. This mean that you don't wait the end of the request to continue,
This delegate must have to implement the following methods :
connection:didReceiveResponse : called after the connection is made successfully and before receiving any data. Can be called more than one time in case of redirection.
connection:didReceiveData : called for each bloc of data.
connectionDidFinishLoading : called only one time upon the completion of the request, if no error.
connection:didFailWithError : called on error.
EXAMPLE: -
NSData *data = [[NSMutableData alloc] init];
NSURL *url_string = [NSURL URLWithString:
#"Your URL"];
NSURLRequest *request = [NSURLRequest requestWithURL:url_string];
NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request
delegate:self];
if (!conn) {
// this is better if you #throw an exception here
NSLog(#"error while starting the connection");
[data release];
}
for each block of raw data received you can append your data here in this method :
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)someData {
[data appendData:someData];
}
connectionDidFinishLoading will call at the end of successfully data receivied
use this code for load more action
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
//scrollView.contentSize.height-scrollView.frame.size.height indicates UItableView scrool end
if (scrollView.contentOffset.y >= scrollView.contentSize.height-scrollView.frame.size.height)
{
if(loadMore)
{
loadmore=no;
//call your Web service
}
}
}
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.
This question already has answers here:
Managing multiple asynchronous NSURLConnection connections
(13 answers)
Closed 8 years ago.
I have two NSURLRequest objects, connecting to a web service and invoking 2 different services.
The problem is that I have a random results, sometimes the first one is displayed first and sometimes the second NSURLRequest is the first.
NSString *urla=#"http://localhost:8080/stmanagement/management/retrieve_dataA/?match_link=";
NSString *uria = [urla stringByAppendingString:self.lien_match];
NSURL *urlla= [ NSURL URLWithString:uria];
NSURLRequest *requesta =[ NSURLRequest requestWithURL:urlla];
NSString *urlb=#"http://localhost:8080/stmanagement/management/retrieve_dataB/?match_link=";
NSString *urib = [urlb stringByAppendingString:self.lien_match];
NSURL *urllb= [ NSURL URLWithString:urib];
NSURLRequest *requestb =[ NSURLRequest requestWithURL:urllb];
connectiona=[NSURLConnection connectionWithRequest:requesta delegate:self];
connectionb=[NSURLConnection connectionWithRequest:requestb delegate:self];
if (connectiona){
webDataa=[[NSMutableData alloc]init];
}
if (connectionb){
webDatab=[[NSMutableData alloc]init];
}
Is that correct what I'm doing? Should I add a small break between the two NSURLRequests?
Because at every view execution I have a random result. (I'm setting the results to two UITableView objects).
I think your "problem" is that self is the connection delegate for both of your connections. These type of connections are asynchronous, so there's no guarantee that A will complete before B. Your code should handle whatever order the web server returns data in.
I suppose you could make the two methods synchronous (don't start B until A completes), but I don't think there's really any need to do that.
The good news is that the NSURLConnectionDelegate callbacks pass you the NSURLConnection object, so you can use that to determine whether you're getting a response to A or B. That information should tell you whether to put the data in the A or B web data object, and whether to update table view A or B, when the request completes. For example:
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// determine which request/connection this is for
if (connection == connectiona) {
[webDataa appendData: data];
} else if (connection == connectionb) {
[webDatab appendData: data];
}
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
// determine which request/connection this is for
if (connection == connectiona) {
NSLog(#"Succeeded! Received %d bytes of data",[webDataa length]);
// TODO(?): update the data source for UITableView (A) and call:
[tableViewA reloadData];
} else if (connection == connectionb) {
NSLog(#"Succeeded! Received %d bytes of data",[webDatab length]);
// TODO(?): update the data source for UITableView (B) and call:
[tableViewB reloadData];
}
// release the connection* and webData* objects if not using ARC,
// otherwise probably just set them to nil
}
This solution requires you keeping connectiona and connectionb as persistent ivars, not local variables in the code you posted. It looks like you're probably doing that, but since you don't show their declaration, I just wanted to be sure.
You should also implement the other delegate callbacks, of course, but the above two should give you a good example of the general solution.