I am trying to get data from a server using the following code.
+ (NSString *) getData:(NSString *)methodName parameters:(NSDictionary *) parameters error:(NSError **)error
{
NSString *body = [UdoziProxy getRequestBody:methodName parameters:parameters];
NSMutableURLRequest *request = [UdoziProxy createRequest:body];
// Send the request .
NSHTTPURLResponse *urlResponse = nil;
NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&urlResponse error:error];
if (responseData == nil || error !=nil) {
return nil;
}
return [[[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding] autorelease];
}
It works fine when the server is running but when I stop the server deliberately, the responseData object has still value and is not nil. How can I handle the situation where either the connection is lost or the server is down ?
You need to set the cache policy on your NSURLRequest object. If the synchronous API still doesn't honour that, you need to switch to using the asynchronous API and throw away the cache request object when you receive it. If that doesn't work, then maybe your network has a transparent proxy which is doing some caching for you.
you have to implement NSURLConnection delegates in
you can get failure status in
the following delegate
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
responseData =nil
}
there you have to make the recieved data to nil value
also its safe to
get data in
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{ }
which indicates that the connection is finished
Related
I've been looking around, saw similar posts, but nothing like this that could give me answers. This is my setup and flow of the app:
User has to login via Facebook, using Facebook Graph. LoginView is presented modally, non animated
When user logins I can retrieve FBID and I use this fbid to send it to my web service (REST)
Web service gets the FBID from the NSURL and matches it with database to retrieve other user info
Using JSONserialization i parse the JSON received from web service and display it in the view
PROBLEM: Everything returns NULL except FBID that I get from Facebook. BUT, if I logout from Facebook and then login, that's when it works.
Here is my code:
viewDidAppear method:
-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:NO];
if (FBSession.activeSession.isOpen) {
[self populateUserDetails];
}
//Connect to WebService
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"http://atnightcorp.com/api/member/id/%#/format/json", fbid]];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection connectionWithRequest:request delegate:self];
NSArray *pics = [member valueForKeyPath:#"photos"];
NSString *picCount = [NSString stringWithFormat:#"%d", [pics count]];
[photosCount setTitle:picCount forState:UIControlStateNormal];
NSLog(#"PHOTO: %#", picCount);
NSLog(#"FB: %#", fbid);
}
I tried putting NSURL request and connection code in viewDidLoad, but then I don't get anything back.
My NSURLConnection methods:
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
data = [[NSMutableData alloc]init];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)theData
{
[data appendData:theData];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
member = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:nil];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
UIAlertView *errorView = [[UIAlertView alloc]initWithTitle:#"Error" message:#"The download could not complete. Please make sure you are connected to internet" delegate:nil cancelButtonTitle:#"Dismiss" otherButtonTitles:nil];
[errorView show];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}
The populateUserDetails method that you have seen above:
- (void)populateUserDetails
{
if (FBSession.activeSession.isOpen) {
[[FBRequest requestForMe] startWithCompletionHandler:
^(FBRequestConnection *connection,
NSDictionary<FBGraphUser> *user,
NSError *error) {
if (!error) {
self.userProfileImage.profileID = user.id;
self.navigationItem.title = user.name;
self.fbid = user.id;
}
}];
}
}
This method basically sets the FBID once user is logged in. Other important things you should know that could help you understand my project:
FBID is set as NSString property in my .H file
All facebook connect thing goes on in AppDelegate
I need to dynamically set the NSURL after I find out who the user is.
if I manually input FBID in NSURL, then it works.
everything should be executed when user logins, I think that the timing of retrieving fbid and receiving data from web service is wrong but I can't get to fix it.
IF you need anything else, I will elaborate more and post more code if needed. -
PLEASE HELP as I've been looking for answers for last 3 days.
Your problem is that the populateUserDetails is called and it returns without waiting the code to be executed (because it's an async task with a completition handler, and when you call the NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"http://atnightcorp.com/api/member/id/%#/format/json", fbid]]; for the first time, the fbid is nuil or not set properly (also you should use self.fbid not fbid since fbid is a property).
So you should try to move the whole code that is handling the request from viewDidAppear into a separate method and you should call that method from startWithCompletionHandler after you set the line with self.fbid = user.id
Also call [super viewDidAppear:animated]; not with NO param (this won't solve your problem but this is the right way to do it)
This might be a dumb question. Sorry if it is.
But Im working on a project that consumes web services. I can connect to the web service and get the data I need fine.
I would like to have a method that returns this data obtained from the web service to the caller. The only problem is that the data is only obtained inside the ConnectionDidFinishLoading method, and I can't access this data from my method.
here is my code, that works fine:
- (NSData *) dataForMethod:(NSString *)webMethod withPostString:(NSString *)postString
{
NSURL *url = [NSURL URLWithString:[SigameWebServiceAddress stringByAppendingFormat:#"%#%#", #"/", webMethod]];
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
NSString *msgLength = [NSString stringWithFormat:#"%d", [postString length]];
[req addValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[req addValue:msgLength forHTTPHeaderField:#"Content-Length"];
[req setHTTPMethod:#"POST"];
[req setHTTPBody: [postString dataUsingEncoding:NSUTF8StringEncoding]];
conn = [[NSURLConnection alloc] initWithRequest:req delegate:self];
if (conn)
{
webData = [NSMutableData data];
}
// I WOULD LIKE TO RETURN WEBDATA TO THE CALLER HERE, BUT WEBDATA IS EMPTY NOW, THE
//connectionDidFinishLoading ONLY GETS CALLED WITH THE DATA I WANT AFTER THE COMPILER
//IS DONE EXECUTING MY METHOD.
}
-(void) connection:(NSURLConnection *) connection didReceiveResponse:(NSURLResponse *) response
{
[webData setLength: 0];
}
-(void) connection:(NSURLConnection *) connection didReceiveData:(NSData *) data
{
[webData appendData:data];
}
-(void) connection:(NSURLConnection *) connection didFailWithError:(NSError *) error
{
NSLog(#"FATAL ERROR");
}
-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
NSLog(#"DONE. Received Bytes: %d", [webData length]);
NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding];
//---shows the XML---
NSLog(#"%#", theXML); //NOW, THIS IS THE DATA I WANT. BUT HOW CAN I RETURN THIS TO
//THE CALLER. I MEAN, THE CALLER THAT CALLED MY METHOD
//+ (NSData *) dataForMethod: withPostString:
}
Any help here is appreciated!
Thanks
There are really two ways to go about this.
Create a delegate interface
Use Blocks
I would strongly advise against using the synchronous methods - unless you are/have created your own asynchronous framework around them (i.e. you are manually starting another thread and executing your synchronous request on that thread). In the long run you will realize you need the requests to be async, and you'll have to re-work everything such that they are.
To give a quick overview of the two options I gave:
1. Create a delegate interface
The idea here is to create a class which performs the request, and create a protocol the caller must implement. When the request is complete, you will invoke a specified method on the delegate with the data:
The protocol might look something like this:
#protocol RequestClassDelegate <NSObject>
- (void)requestCompleted:(ResponseClass *)data;
- (void)requestError:(NSError *)error;
#end
The class which makes the request might look something like this:
#interface RequestClass : NSObject
- (void)makeRequest:(id<RequestClassDelegate>)delegate;
#end
And the request class implementation might contain some of the following, in addition to your connection logic:
#implementation RequestClass
{
__weak id<RequestClassDelegate> _delegate;
}
// Connection Logic, etc.
- (void)makeRequest:(id<RequestClassDelegate>)delegate
{
_delegate = delegate;
// Initiate the request...
}
-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding];
// Processing, etc.
// Here we'll call the delegate with the result:
[_delegate requestCompleted:theResult];
}
#end
2. Use Blocks
This solution is much the same as the first solution - but, a bit more elegant in my opinion. Here, we'll change the RequestClass to use blocks instead of a delegate:
typedef void (^requestCompletedBlock)(id);
typedef void (^requestErrorBlock)(NSError *);
#interface RequestClass : NSObject
#property (nonatomic, copy) requestCompletedBlock completed;
#property (nonatomic, copy) requestErrorBlock errored;
- (void)makeRequest:(requestCompletedBlock)completed error:(requestErrorBlock)error;
#end
And the implementation of that might look something like this:
#implementation RequestClass
#synthesize completed = _completed;
#synthesize errored = _errored;
// Connection Logic, etc.
- (void)makeRequest:(requestCompletedBlock)completed error:(requestErrorBlock)error
{
self.completed = completed;
self.errored = error;
// Initiate the request...
}
-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding];
// Processing, etc.
// Here we'll call the delegate with the result:
self.completed(theResult);
}
#end
It sounds like you are trying to use return the data synchronously from your method, but you are using an asynchronous method (using an NSURLConnection and presumably calling its start method) to begin retrieving data. If you really want your method to return its result synchronously, read on. As #Steve says in another answer, however, you may also reconsider your interface design and instead implement it using an asynchronous approach and use his recommendations for either a delegate or block-based interface.
If you want to return the data synchronously from your method, use a synchronous request. So change this part of your code:
conn = [[NSURLConnection alloc] initWithRequest:req delegate:self];
[conn start]; // I presume you have this somewhere
if (conn)
{
webData = [NSMutableData data];
}
with something more like this:
NSURLResponse *response = nil;
NSError *error = nil;
webdata = [NSURLConnection sendSynchronousRequest:req returningResponse:&response error:&error];
if (webdata) {
return webdata;
}
else {
// Handle error by looking at response and/or error values
return nil;
}
You will no longer need any of your delegate code if you use this approach. You will be limited in some ways though. For example, if your web service requires authentication via something other than URL parameters you can't use this approach.
Steve's answer is great and I can only suggest the way using blocks. Actually, as I am new into Objective-C I implemented the approach steve outlined. It works perfectly.
The Post for more details and my own point of view you can find here:
http://kerkermeister.net/how-to-build-an-cocos2d-ios-app-communicating-with-a-restful-api-the-sequence/
The Post contains all the tiny steps you need to follow to get Steve's solution approach with blocks working. That includes:
- an updateable view that will render information as soon as retrieved from Web API asynchronously
- a controller invoking the HTTP request to the Web API
- the actual HttpRequest class that uses iOS standard NSURLConnections
- a model class that uses blocks as callbacks to update its data
Your going to have to either implement a separate method in which you use the data once the data has been returned by the connectionDidFinishLoading method or make the request synchronously. The reason I believe the above does not work is because the request is happening on a separate thread, so the main thread continues, but does not actually have the data.
This is a good way to do that if synchronous is what you want:
Does all NSURLConnections connect asynchronously? iOs
In order to download data from webserivce - use NSURLSession -
A URL session task that returns downloaded data directly to the app in memory.
// 1. create NSURL link to your webservice
NSString *dataUrl = #"DATA_LINK_TO_WEBSERVICE";
NSURL *url = [NSURL URLWithString:dataUrl];
// 2. create a NSURLSessionDataTask
NSURLSessionDataTask *downloadTask = [[NSURLSession sharedSession]
dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
//Handle response here
}];
// 3.resume the task
[downloadTask resume];
Refernces:
apple documentation refrence:
https://developer.apple.com/documentation/foundation/nsurlsessiondatatask?language=objc
Raywanderlich great cookbook:
https://www.raywenderlich.com/2392-cookbook-using-nsurlsession
Your going to need to parse the XML that comes back. There are some good Objective C XML parsers out there. One in particular is made for ease of use....
http://nfarina.com/post/2843708636/a-lightweight-xml-parser-for-ios
It's a very light weight parser for extracting the values you want from XML. I've used many times with great success and little hassle. Here is how I query a web address and turn it into data.
NSString *query = [NSString stringWithFormat:#"http://WEB_ADDRESS_FOR_XML];
NSURL *URL = [NSURL URLWithString:query];
NSData *data = [NSData dataWithContentsOfURL:URL];
Or with NSURLConnection, in the did receive data:
-(void) connection:(NSURLConnection *) connection didReceiveData:(NSData *) data
{
//USE THE DATA RETURNED HERE....
}
Then use the Parser from my link to get the contents:
SMXMLDocument *document = [SMXMLDocument documentWithData:data error:NULL];
NSLog("\nXML Returned:%#",document);
I have a doubt regarding downloading data from a web service. One way is to download it in a single line mentioned below.
NSString *returnString = [[NSString alloc] initWithData:[NSURLConnection sendSynchronousRequest:urlrequest returningResponse:nil error:nil] encoding:NSUTF8StringEncoding];
And the other way to get it is via connectionDidFinishLoading
[..]
NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:urlrequest delegate:self];
NSHTTPURLResponse *response;
[NSURLConnection sendSynchronousRequest: urlrequest returningResponse: &response error: nil];
if( theConnection )
{
webData = [[NSMutableData data] retain];
}
else
{
NSLog(#"theConnection is NULL");
}
}
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[webData setLength: 0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[webData appendData:data];
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
NSLog(#"ERROR with theConenction");
[connection release];
[webData release];
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
NSLog(#"DONE. Received Bytes: %d", [webData length]);
NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length: [webData length] encoding:NSUTF8StringEncoding];
}
Is there any difference between these two? NSURLConnection delegate method is not called when I use a separate class to parse the response.
You're using sendSynchronousRequest:returningResponse:error: which does not call any delegates methods because it doesn't need to: when you call it, the main thread stops until the request is finished and you get the response.
If you want to make an asynchronous request, use connectionWithRequest:delegate:. I recommend to always do asynchronous responses since the synchronous request blocks the main thread and your UI can't respond during that time. Animations will become interrupted. Scrolling becomes jerky. If you do want to use synchronous requests you should do it in a background thread.
The -sendSynchronousRequest:returningResponse:error: method blocks the main-thread (whenever it runs on the main-thread of course, since it's possible to run this method from any other thread, but I believe this is not recommended).
The methods using the delegates are asynchronous, the methods will fire and the results will (at some point in the future) be returned in the delegate methods. This gives the user a more smooth experience, since the main-thread will not be blocked.
Edit: personally I hardly ever use the -sendSynchronousRequest:returningResponse:error: method for the aforementioned reasons. Most of the time I use this method when I need to build something quickly, for example a proof-of-concept. I guess one could use the method for small downloads, yet if a timeout occurs (because for some reason the server is down) the whole UI will be blocked for (I believe) 2 minutes, which would be very annoying for the enduser.
An excellent demonstration to clarify your doubt is available in apple sample apps.You can refer Apple's sample app for a better understanding of asynchronous request and parsing data in separate class.
I am trying to read certificates from various URLs in iOS. My code however is not working well - the array that should return the information I need always returns null.
What am I missing?
- (void)findCertificate:(NSString *)url
{
NSInputStream*input = [[NSInputStream inputStreamWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:#"https://store.writeitstudios.com"]]] retain];
[input setDelegate:self];
[input scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
[input open];
NSLog(#"Status: %i",[input streamStatus]);
}
- (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode
{
NSLog(#"handle Event: %i",eventCode);
if (eventCode == NSStreamStatusOpen)
{
NSArray *certificates = (NSArray*)CFReadStreamCopyProperty((CFReadStreamRef)aStream, kCFStreamPropertySSLPeerCertificates);
NSLog(#"Certs: %#",CFReadStreamCopyProperty((CFReadStreamRef)aStream, kCFStreamPropertySSLPeerCertificates));
if ([certificates count] > 0) {
SecCertificateRef certificate = (SecCertificateRef)[certificates objectAtIndex:0];
NSString *description = (NSString*)SecCertificateCopySubjectSummary(certificate);
NSData *data = (NSData *)SecCertificateCopyData(certificate);
NSLog(#"Description: %#",description);
}
}
}
And yes, I am aware that I am leaking memory. This is just a snippet.
Let me explain what you're doing here and why it's wrong:
You are loading the contents of the URL https://store.writeitstudios.com (i.e. the HTML) synchronously into an NSData (a data buffer). Note that you are not loading any certificates (well, technically NSURL will load them internally, but this code is most definitely not putting them into the NSData)
You are opening an input stream and sticking the data (a bit of HTML, no certificates!) into it.
You have implemented NSStream's delegate method stream:handleEvent: and are attempting to read the kCFStreamPropertySSLPeerCertificates property. This property will be empty since the stream contains only a bit of HTML data, nothing else.
You are casting the empty property to an NSArray.
The loop is not executed because the array is NULL.
Using NSStream/CFStream is not necessary for the task at hand. And most definitely you don't have to go through NSURLConnection first and then through NSStream.
To retrieve SSL server certificates, stick to a simple, asynchronous NSURLConnection and use its delegate methods to access the certificates:
// Method to begin the asynchronous download
- (void)beginCertificateDownload:(NSURL *)url
{
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[connection start];
}
// NSURLConnection Delegate Methods
- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace
{
return [[protectionSpace authenticationMethod] isEqualToString:NSURLAuthenticationMethodServerTrust];
}
- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
// extract the certificates
SecTrustRef trustRef = [[challenge protectionSpace] serverTrust];
CFIndex count = SecTrustGetCertificateCount(trustRef);
for (CFIndex i = 0; i < count; i++) {
SecCertificateRef certRef = SecTrustGetCertificateAtIndex(trustRef, i);
CFStringRef certSummary = SecCertificateCopySubjectSummary(certRef);
NSLog(#"%#", certSummary);
// do whatever you need with the certificates here
// don't forget to copy them if you need to keep them
// around beyond the scope of this method
}
// I'm assuming you're not interested in actually loading the contents of the URL, so cancel
[[challenge sender] cancelAuthenticationChallenge:challenge];
// you'll also want to release the connection object at some point
}
i'm a beginner to iphone.i want to create a login page for my application.i cant figure out how to connect to a php page and retrieve corresponding data from mysql database to the iphone.could any one guide me how to go about it.
what does the iphone have to do with a connection between php and mysql ?
PHP will run with on a web server probably apache installed on some computer and it will connect to a MySQL db .. and u will access that php page from your iphone with a browser. Not sure what part will the iphone have in all this other than providing the browser
You might want to have a look at NSURLRequest which you can use with a NSURLConnection to send e.g. GET-Parameters to a URL. You can then implment the NSURLConnectionDelegate to respond to incoming data:
1) setup connection
receivedData =[NSMutableData data];
NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:url]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:20.0];
NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
2) Setup delegate methods in self:
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse*)response {
NSHTTPURLResponse * httpResponse = (NSHTTPURLResponse *) response;
if([httpResponse statusCode]==200)
[receivedData setLength:0];
else
NSLog(#"Http-Reponse %u",[httpResponse statusCode]);
// HANDLE ERROR!
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
// append the new data to the receivedData
// receivedData is declared as a method instance elsewhere
[receivedData appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
// HANDLE THE CONNECTION ERROR
// release the connection, and the data object
[connection release];
// receivedData is declared as a method instance elsewhere
[receivedData release];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
// receivedData contains the data
// convert to string:
NSLog(#"finished loading: %#",[[[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding] autorelease]);
[connection release];
[receivedData release];
}
You'll want to expose the authentication functionality as a web service, then use the URL Loading code posted by Felix L. to initiate an actual connection to the web service.
You'll probably want to send a response from the server as XML, if so, you'll parse that response with an NSXMLParser, otherwise you can just send the response in whatever format you'd like and parse it appropriately.