I'm fairly new to iOS development and I've been stuck on this bug for a while. I'm making a simple app the uses a web service. Right now I currently have two view controllers. A login view controller (with its NIB file) and a main view controller (with its NIB file). When I created the app I chose an empty application so I don't have a storyboard. Instead I'm using UINavigationController. When I run my code I get the following error after entering my username and password and pressing submit in the login view:
Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UIKeyboardTaskQueue waitUntilAllTasksAreFinished] may only be called from the main thread.'
This is the code I have for my submit button:
-(IBAction)logIn:(id)sender{
UIApplication *application = [UIApplication sharedApplication];
application.networkActivityIndicatorVisible = YES;
[_loginNetworkingContorller checkCredentialsWithUsername:self.username.text withPassword:self.password.text completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(!error){
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
NSLog(#"SUCESS");
NSDictionary *credentials = #{self.username.text: self.password.text};
[KeychainUserPass save:#"MY APP" data:credentials];
UIViewController *mainView = [[RDMainViewController alloc] initWithNibName:#"RDMainViewController" bundle:nil];
[self.navigationController pushViewController:mainView animated:YES];
}
else{
NSLog(#"ERROR");
}
}
else{
NSLog(#"ERROR");
}
}];
}
And here is the code for the following function
[_loginNetworkingContorller checkCredentialsWithUsername:self.username.text withPassword:self.password.text completionHandler:^(NSData *data, NSURLResponse *response, NSError *error)
-(void)checkCredentialsWithUsername:(NSString *)username withPassword:(NSString *)password completionHandler:(void (^)(NSData *data,NSURLResponse *response, NSError *error))myCompletion
{
NSString *requestString = #"SOME WEBSITE";
NSURL *url = [NSURL URLWithString:requestString];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
NSData *userPasswordData = [[NSString stringWithFormat:#"%#:%#", username, password] dataUsingEncoding:NSUTF8StringEncoding];
NSString *base64EncodedCredential = [userPasswordData base64EncodedStringWithOptions:0];
NSString *authString = [NSString stringWithFormat:#"Basic %#", base64EncodedCredential];
NSURLSessionConfiguration *sessionConfig=[NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.HTTPAdditionalHeaders=#{#"Authorization":authString};
self.session=[NSURLSession sessionWithConfiguration:sessionConfig];
NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
myCompletion(data, response, error);
}];
[dataTask resume];
}
I'm a stuck right now and am not really sure what the issue is especially since I don't do anything with the keyboard. I have a feeling there is an issue with my blocks but I'm not exactly sure what the issue is. Any help would be greatly appreciated.
Hey I had this same issue after I received my response from my web call. I was able to solve it be doing the following:
//do something with response
dispatch_async(dispatch_get_main_queue()) { () -> Void in
// continue with program by calling next step on main thread
}
I think if you push to the next view controller iOS attempts to do it on not the main thread, causing the error, but I'm not 100% is that is accurate
Related
I have a method that returns a string usually locally, but with a backup from the Web. I was retrieving some JSON using dataWithContentsOfUrl but want to switch to using a Session object which is better for the UI and also--if I am not mistaken--allows the server to set a sessionId on the phone, however, I'm struggling with the async issue.
With the old code, I just returned the JSON but I'm struggling with how to do this for the asynchronous result. I can't change the calling method which returns a string. What can I do with the asynchronous Api call to use the data that is retrieved?
async:
-(void)getAsyncAnswerFor:(NSString*) str {
NSString *surl = [NSString stringWithFormat: #"https://~.com//api.php?q=%#",str];
NSURL *url = [NSURL URLWithString:surl];
NSURLSessionDataTask *downloadTask = [[NSURLSession sharedSession]
dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
//HOW DO I PASS THIS BACK TO THE CALLING METHOD OR IS THAT IMPOSSIBLE
}];
[downloadTask resume];
}
sync
-(NSString*)getAnswerFor:(NSString*) str {
NSError *error;
NSString *surl = [NSString stringWithFormat: #"https://~.com//api.php?q=%#",str];
NSData *data = [NSData dataWithContentsOfURL: [NSURL URLWithString:surl]];
NSMutableArray *json = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
//process JSON
if (error) {
return #"";
}
return #"processed JSON";
}
Would appreciate any suggestions.
If what I want to do is totally impossible, is it possible to set a sessionID on the phone without the Session object? I know setting a session ID is is not the greatest approach, but I'm trying to avoid a lot of authentication overhead.
You can pass a block to your asynchronous function and then call it when the url session completion handler is called. This is a trivial example:
- (void)doSomethingWithBlock:(void (^)(double, double))block {
...
block(21.0, 2.0);
}
I lifted this ^^ from the Apple Docs but you might be able to do something like this: (Note: I didn't check this in a compiler!)
-(void)getAsyncAnswerFor:(NSString*) str completion:(void (^)(NSData, NSURLResponse, NSError))block {
NSString *surl = [NSString stringWithFormat: #"https://~.com//api.php?q=%#",str];
NSURL *url = [NSURL URLWithString:surl];
NSURLSessionDataTask *downloadTask = [[NSURLSession sharedSession]
dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
block(data, response, error);
}];
[downloadTask resume];
}
You'll need to be careful if you try to reference self anywhere in the blocks.
I am new to Objective C and iOS development in general. I am trying to create an app that would make an http request and display the contents on a label.
When I started testing I noticed that the label was blank even though my logs showed that I had data back. Apparently this happens because the the response is not ready when the label text gets updated.
I put a loop on the top to fix this but I am almost sure there's got to be a better way to deal with this.
ViewController.m
- (IBAction)buttonSearch:(id)sender {
HttpRequest *http = [[HttpRequest alloc] init];
[http sendRequestFromURL: #"https://en.wiktionary.org/wiki/incredible"];
//I put this here to give some time for the url session to comeback.
int count;
while (http.responseText ==nil) {
self.outputLabel.text = [NSString stringWithFormat: #"Getting data %i ", count];
}
self.outputLabel.text = http.responseText;
}
HttpRequest.h
#import <Foundation/Foundation.h>
#interface HttpRequest : NSObject
#property (strong, nonatomic) NSString *responseText;
- (void) sendRequestFromURL: (NSString *) url;
- (NSString *) getElementBetweenText: (NSString *) start andText: (NSString *) end;
#end
HttpRequest.m
#implementation HttpRequest
- (void) sendRequestFromURL: (NSString *) url {
NSURL *myURL = [NSURL URLWithString: url];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL: myURL];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *task = [session dataTaskWithRequest: request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
self.responseText = [[NSString alloc] initWithData: data
encoding: NSUTF8StringEncoding];
}];
[task resume];
}
Thanks a lot for the help :)
Update
After reading a lot for the very useful comments here I realized that I was missing the whole point. So technically the NSURLSessionDataTask will add task to a queue that will make the call asynchronously and then I have to provide that call with a block of code I want to execute when the thread generated by the task has been completed.
Duncan thanks a lot for the response and the comments in the code. That helped me a lot to understand.
So I rewrote my procedures using the information provided. Note that they are a little verbose but, I wanted it like that understand the whole concept for now. (I am declaring a code block rather than nesting them)
HttpRequest.m
- (void) sendRequestFromURL: (NSString *) url
completion:(void (^)(NSString *, NSError *))completionBlock {
NSURL *myURL = [NSURL URLWithString: url];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL: myURL];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *task = [session dataTaskWithRequest: request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
//Create a block to handle the background thread in the dispatch method.
void (^runAfterCompletion)(void) = ^void (void) {
if (error) {
completionBlock (nil, error);
} else {
NSString *dataText = [[NSString alloc] initWithData: data encoding: NSUTF8StringEncoding];
completionBlock(dataText, error);
}
};
//Dispatch the queue
dispatch_async(dispatch_get_main_queue(), runAfterCompletion);
}];
[task resume];
}
ViewController.m
- (IBAction)buttonSearch:(id)sender {
NSString *const myURL = #"https://en.wiktionary.org/wiki/incredible";
HttpRequest *http = [[HttpRequest alloc] init];
[http sendRequestFromURL: myURL
completion: ^(NSString *str, NSError *error) {
if (error) {
self.outputText.text = [error localizedDescription];
} else {
self.outputText.text = str;
}
}];
}
Please feel free to comment on my new code. Style, incorrect usage, incorrect flow; feedback is very important in this stage of learning so I can become a better developer :)
Again thanks a lot for the replies.
You know what, use AFNetworking to save your life.
Or just modify your HttpRequest's sendRequestFromURL:
- (void)sendRequestFromURL:(NSString *)url completion:(void(^)(NSString *str, NSError *error))completionBlock {
NSURL *myURL = [NSURL URLWithString: url];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL: myURL];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *task = [session dataTaskWithRequest: request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
dispatch_async(dispatch_get_main_queue(), ^{
if (error) {
completionBlock(nil, error);
} else {
completionBlock([[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding], error);
}
});
}];
[task resume];
}
and invoke like this
[http sendRequestFromURL:#"https://en.wiktionary.org/wiki/incredible" completion:^(NSString *str, NSError *error) {
if (!error) {
self.outputLabel.text = str;
}
}];
Rewrite your sendRequestFromURL function to take a completion block:
- (void) sendRequestFromURL: (NSString *) url
completion: (void (^)(void)) completion
{
NSURL *myURL = [NSURL URLWithString: url];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL: myURL];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *task = [session dataTaskWithRequest: request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error)
{
self.responseText = [[NSString alloc] initWithData: data
encoding: NSUTF8StringEncoding];
if (completion != nil)
{
//The data task's completion block runs on a background thread
//by default, so invoke the completion handler on the main thread
//for safety
dispatch_async(dispatch_get_main_queue(), completion);
}
}];
[task resume];
}
Then, when you call sendRequestFromURL, pass in the code you want to run when the request is ready as the completion block:
[self.sendRequestFromURL: #"http://www.someURL.com&blahblahblah",
completion: ^
{
//The code that you want to run when the data task is complete, using
//self.responseText
}];
//Do NOT expect the result to be ready here. It won't be.
The code above uses a completion block with no parameters because your code saved the response text to an instance variable. It would be more typical to pass the response data and the NSError as parameters to the completion block. See #Yahoho's answer for a version of sendRequestFromURL that takes a completion block with a result string and an NSError parameter).
(Note: I wrote the code above in the SO post editor. It probably has a few syntax errors, but it's intended as a guide, not code you can copy/paste into place. Objective-C block syntax is kinda nasty and I usually get it wrong the first time at least half the time.)
If you want easy way then Don't make separate class for call webservice. Just make meethod in viewController.m instead. I mean write sendRequestFromURL in your viewController.m and update your label's text in completion handler something like,
- (void) sendRequestFromURL: (NSString *) url {
NSURL *myURL = [NSURL URLWithString: url];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL: myURL];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *task = [session dataTaskWithRequest: request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
dispatch_async(dispatch_get_main_queue(), ^{
self.responseText = [[NSString alloc] initWithData: data
encoding: NSUTF8StringEncoding];
self.outputLabel.text = self.responseText;
})
}];
[task resume];
}
I'm working on my first app that integrates with a web service. Right now I have two views with their respective view controllers. I have a login view, which is where users will login to the app and I will verify and store there login credentials and I have a main view which shows all the users info from the web service. My two views work correctly individually however after verifying the credentials of the user on my login view I want to switch views to my login view. To do this I'm using UIViewController. Here is my code for when the login button is pressed:
-(IBAction)logIn:(id)sender{
//Show network activity is happening
UIApplication *application = [UIApplication sharedApplication];
application.networkActivityIndicatorVisible = YES;
//Validate credentials
[_loginNetworkingContorller checkCredentialsWithUsername:self.username.text withPassword:self.password.text completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(!error){
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
//if we get back a successful status code save username and password in keychain.
NSLog(#"SUCESS");
NSDictionary *credentials = #{self.username.text: self.password.text};
[KeychainUserPass save:#"INSERT APP NAME HERE" data:credentials];
NSLog(#"go to new page");
//print response from webservice for debugging purposes
NSMutableDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"%#", jsonObject);
//switch to new view controller
UIViewController *mainController = [[RDMainViewController alloc] initWithNibName:#"RDMainViewController" bundle:nil];
[self.navigationController pushViewController:mainController animated:NO];
}
else{
//Error case, handle it.
NSLog(#"ERROR");
}
}
else{
//Error case, handle it.
NSLog(#"ERROR");
}
}];
}
And here checkCredentialsWithUsername method:
-(void)checkCredentialsWithUsername:(NSString *)username withPassword:(NSString *)password completionHandler:(void (^)(NSData *data,NSURLResponse *response, NSError *error))myCompletion
{
//Create request URL
NSString *requestString = #"WEB_SERVICE_URL";
NSURL *url = [NSURL URLWithString:requestString];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
//Store password and user name for authentication
NSData *userPasswordData = [[NSString stringWithFormat:#"%#:%#", username, password] dataUsingEncoding:NSUTF8StringEncoding];
NSString *base64EncodedCredential = [userPasswordData base64EncodedStringWithOptions:0];
NSString *authString = [NSString stringWithFormat:#"Basic %#", base64EncodedCredential];
//Create an NSURL session
NSURLSessionConfiguration *sessionConfig=[NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.HTTPAdditionalHeaders=#{#"Authorization":authString};
self.session=[NSURLSession sessionWithConfiguration:sessionConfig];
NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
myCompletion(data, response, error);
}];
[dataTask resume];
}
My issue is that it's taking an incredibly long time to switch views. Like sometimes over a minute. At first I thought it was the network connection but then I printed the data I was receiving from the web service and it was appearing very quickly. Even after I printed the data it was still taking a very long time for views to switch. I'm not really sure why but I think it has to do with the way I'm doing my blocks. Any idea why it's taking me such a long time to switch views?
Any help would be greatly appreciated.
#Danyun was right. I needed to do the following:
if (httpResp.statusCode == 200) {
//if we get back a successful status code save username and password in keychain.
NSLog(#"SUCESS");
NSDictionary *credentials = #{self.username.text: self.password.text};
[KeychainUserPass save:#"INSERT APP NAME HERE" data:credentials];
NSLog(#"go to new page");
//print response from webservice for debugging purposes
NSMutableDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"%#", jsonObject);
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
//test to make sure we are on the main Queue for UI update
//switch to the new view controller
UIViewController *mainController = [[RDMainViewController alloc] initWithNibName:#"RDMainViewController" bundle:nil];
[self.navigationController pushViewController:mainController animated:NO];
}];
}
I am trying to fetch a JSON-feed but somehow the command is never executed. I have placed a NSLog just before the session gets called and that actually gets output on the console. The NSLog later "test" never gets output. I can't find out where the problem is. Another JSON request works just fine. Here is the code:
NSLog(#"fetchClassified started!");
// connect to webserver and ask for the feed
NSURL *url = [NSURL URLWithString:#"http://test.server/services/rest/v1/interface2?id=22"];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
// create a task that transfers the feed from the server
NSURLSessionTask *dataTask = [self.session dataTaskWithRequest:req
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
NSDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data
options:0 error:nil];
NSLog(#"test %#", jsonObject);
self.classified = jsonObject[#"tasks"];
NSLog(#"%#", self.classified);
// put the output on the main queue (UI has to run always on main thread)
dispatch_async(dispatch_get_main_queue(), ^{
self.textView.text =self.classified;
});
}
];
[dataTask resume];
Thank you in advance for any hint on this!
JoeFryer solved it. self.session was nil.
I'm relatively new to iOS development but I'm working on an application to get a better understanding of development. I'm working with a web service and want to check the credentials a user enters. To do this I am making a simple get request with their credentials and then checking the http status for 200. Here is my code below:
-(BOOL)checkCredentials:(NSString *)username withPassword:(NSString *)password{
NSString *requestString = #"SOME URL";
NSURL *url = [NSURL URLWithString:requestString];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
NSData *userPasswordData = [[NSString stringWithFormat:#"%#:%#", username, password] dataUsingEncoding:NSUTF8StringEncoding];
NSString *base64EncodedCredential = [userPasswordData base64EncodedStringWithOptions:0];
NSString *authString = [NSString stringWithFormat:#"Basic %#", base64EncodedCredential];
NSURLSessionConfiguration *sessionConfig=[NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.HTTPAdditionalHeaders=#{#"Authorization":authString};
self.session=[NSURLSession sessionWithConfiguration:sessionConfig];
__block BOOL success = NO;
dispatch_semaphore_t sema = dispatch_semaphore_create(0);
NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(!error){
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
success = YES;
}
}
NSMutableDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"%#", jsonObject);
dispatch_semaphore_signal(sema);
}];
dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
[dataTask resume];
return success;
}
I was going to use a semaphore to wait for the block to complete so I can check the status code and then return. But first it seems like my code just hangs, and I think that because I don't have a release, but that's not allowed with ARC. I'm not sure why it's hanging. Is there a better way to wait for the block to complete (without a semaphore) so I can return whether my credentials are valid?
Also is there a better way to pass the username and password so that it's not possible for someone to spoof the username and password?
Any help would be greatly appreciated.
Think simple!
Make your own completionHandler so that you won't deal with the return anymore, the caller will take the responsibility of result verification instead.
There's one thing you need to keep in mind, that if you want to modify anything related to UI (User Interface), you need to dispatch your completion block to main queue or you will get unexpected behavior, see more detail here.
Change your return type to void and add a completion block:
-(void)checkCredentials:(NSString *)username withPassword:(NSString *)password completionHandler:(void (^)(NSData *data, NSURLResponse *response, NSError *error))myCompletion
{
NSString *requestString = #"http://google.com";
NSURL *url = [NSURL URLWithString:requestString];
NSURLRequest *req = [NSURLRequest requestWithURL:url];
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
// Here you return exactly what the NSURLSessionDataTask downloaded
// and pass it to the caller as an another completion block
myCompletion(data, response, error);
}];
[dataTask resume];
}
Caller's code, I assume that self is the caller:
[self checkCredentials:#"" withPassword:#"" completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(!error){
// Result verification's here
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
NSLog(#"SUCESS");
}
}
}];
You code stops waiting for a semaphore and [dataTask resume] is never executed.
dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER); <=== waits here
[dataTask resume]; <=== never reached
I'd suggest not using the semaphore here. Do the work in your block instead.
As to username/password. If you worry about spoofing then SSL layer on top of HTTP is the answer.
This is a really dangerous pattern, because this call is going to block until the network request completes. If this is on the main thread, your app will stop responding and the watchdog may kill you.
That warning aside, the reason the block doesn't complete is because the network task is never started. You trap on your semaphore before you call resume, so your task never runs. I would also, personally use a dispatch_group to do the waiting.
To make it better, you would need to rewrite it asynchronously. Basically have your app continue to function, maybe disable the inputs, until the call completes, then run a block to re-enable them, or show an error:
// Assume your login button and whatever are exposed as properties here
self.loginButton.enabled = NO;
NSURLSessionDataTask *dataTask = [self.session dataTaskWithRequest:req completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if(!error){
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
success = YES;
}
}
NSMutableDictionary *jsonObject = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil];
NSLog(#"%#", jsonObject);
// Need to be back on the main queue, the call is complete
self.loginButton.enabled = YES;
}];
[dataTask resume];
Or, just to keep it the way you have it, but resolve the immediate issue, re-order your trap so that it happens after the task resumes:
[dataTask resume];
dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER); // might want to time out here instead of waiting forever
return success;