I have a large NSArray I am wanting to split into chunks and send to my web server, upon completion of each chunk I then need to update the fields in my SQLite DB that relate to each item in each array chunk.
This is the code I am currently running, where I try to use a call back to receive success or failure then update my local SQLite DB where appropriate.
- (void)postlowData:(NSArray *)lowMArray Callback:(void (^)(NSError *error, BOOL success))callback;
{
// Currently this method is sending the whole lowMArray
// What I want to do is Split lowMArray into a chunkArray (where chunk is 20 of the leading items from lowMArray)
// I would then send chunkArray with the following code, when I receive a response I then want to update local SQLite DB with result and recall this method to start on the next 20 chunks.
// Create Json data from lowMArray
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:lowMArray
options:NSJSONWritingPrettyPrinted
error:nil];
// Construct post request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#/lows", _silServerBaseUrl]]];
request = [self applyAuth:request];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json; charset=UTF-8" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:jsonData];
// Send post request
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
NSURLSessionDataTask *dataTask = [manager dataTaskWithRequest:request completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
if (error) {
// NSLog(#"Response Failed!");
callback(error, NO);
} else {
// NSLog(#"Response Success!");
callback(error, YES);
// On success add itmes from lowChunkArray so that you can adjust sent_Flag later
}
}];
[dataTask resume]; // runs task
}
The issue I am running into is that when I run this code if I am splitting the array into chunks sending the chunk adjusting the main array for the next chunk I don't get a confirmed callback till the very end of all the requests, at which point I have lost track of what success or failure?
Maybe I am going about this the wrong way?
Update
I am now trying to do this using AFHTTPRequestOperation which seems to be working as a batch upload however the
setHTTPBody:jsonData
Never seems to make it to the server.
I used this Batch of Operations example to help me construct this method however as I said above the JSON data never makes it to the server.
- (void)postlowData:(NSArray *)lowMArray;
{
NSLog(#"Syncing Local");
NSArray *chunklow = [[NSArray alloc] init];
NSMutableArray *mutableOperations = [NSMutableArray array];
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"%#/lows", _silServerBaseUrl]];
//Test: creating 10 things to send
for (int i = 0; i < 10; i++) {
if ([lowMArray count] > 0) {
if ([lowMArray count] >= 20) {
low = [lowMArray subarrayWithRange:NSMakeRange(0, 20)];
} else if ([lowMArray count] < 20) {
low = [lowMArray subarrayWithRange:NSMakeRange(0, [lowMArray count])];
}
}
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:low
options:NSJSONWritingPrettyPrinted
error:nil];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
request = [self applyAuth:request];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json; charset=UTF-8" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:jsonData];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
[mutableOperations addObject:operation];
}
NSArray *operations = [AFURLConnectionOperation batchOfRequestOperations:mutableOperations progressBlock:^(NSUInteger numberOfFinishedOperations, NSUInteger totalNumberOfOperations) {
NSLog(#"%lu of %lu complete", numberOfFinishedOperations, totalNumberOfOperations);
} completionBlock:^(NSArray *operations) {
NSLog(#"All operations in batch complete");
NSLog(#"Syncing complete");
}];
[[NSOperationQueue mainQueue] addOperations:operations waitUntilFinished:NO];
}
For your problem of splitting insertion of a large array into chunks to be inserted to a DB via network operations, an NSOperationQueue can be created that will allow you to add a separate operation for each chunk of data to be inserted.
The queue can be set to run in a serial manner so that each operation will need to be complete before the next one is started.
Using a queue makes the multiple operations more manageable than having the flow be controlled by callbacks.
In summary, you create a queue and set its maximum concurrent operation count to 1. Then create an NSOperation subclass that performs the necessary steps to insert data into the database. Each chunk of data will correspond to a separate operation that will be added to the queue. Each operation will be performed in series until all are complete.
Here is an outline for the solution:
// Create a new queue to hold network operations.
self.operationQueue = [[NSOperationQueue alloc] init];
self.operationQueue.maxConcurrentOperationCount = 1;
// Split the large array into chunks of 20 items each.
NSInteger chunkSize = 20;
NSInteger i = 0;
NSInteger total = [lowMArray count];
while (i < total) {
NSInteger j = i;
NSMutableArray *chunk = [NSMutableArray alloc] init];
while (j < i + chunkSize - 1 && j < total) {
[chunk addObject:lowMArray[j]];
j++;
}
MyOperation *myOperation = [[MyOperation alloc] initWithArray:chunk];
self.operationQueue.addOperation(myOperation)
i += chunkSize;
}
MyOperation.h:
#interface MyOperation : NSOperation
- (instancetype)initWithArray:(NSArray *)chunk;
#property NSArray *chunk;
#end
MyOperation.m:
#implementation MyOperation
- (instancetype)initWithArray:(NSArray *)chunk
{
if (self = [super init]) {
self.chunk = chunk;
}
return self;
}
- (void)main
{
// Create Json data from lowMArray
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:self.chunk
options:NSJSONWritingPrettyPrinted
error:nil];
// Construct post request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#/lows", _silServerBaseUrl]]];
request = [self applyAuth:request];
[request setHTTPMethod:#"POST"];
[request setValue:#"application/json; charset=UTF-8" forHTTPHeaderField:#"Content-Type"];
[request setHTTPBody:jsonData];
// Send post request
AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
NSURLSessionDataTask *dataTask = [manager dataTaskWithRequest:request completionHandler:^(NSURLResponse *response, id responseObject, NSError *error) {
if (error) {
// NSLog(#"Response Failed!");
} else {
// NSLog(#"Response Success!");
}
}];
[dataTask resume]; // runs task
}
#end
AFNetworking has support for its own NSOperation subclass in AFHTTPRequestOperation. An example can be found here. Also, the AFNetworking GitHub repository has an example for batch operations.
Based on your revised question, setting the completion block of each AFHTTPRequestOperation to handle the response and error can help to debug the problem.
Here is how it is done:
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation * _Nonnull operation, id _Nonnull responseObject) {
NSString* decodedResponse = [[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding];
NSLog(#"response %#", decodedResponse);
} failure:^(AFHTTPRequestOperation * _Nonnull operation, NSError * _Nonnull error) {
NSLog(#"error %#", error);
}];
It would be inserted after AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];.
I have the following problem. I have a Model, called User. When the user now logins with Facebook, my app checks if the user exists already in the database. To not freeze the UI (since I'm coming from Android) I thought to use NSURLConnection sendAsynchronousRequest. What worked at first was the following:
My User Model had a method to do the whole task of the AsynchronousRequest and then when finished would set a variable to loading. Then other classes, could simply check with
while ( !user.loading ) if the Request was finished or not. The problem that came here to me, was, that now, I had to put this method in every Model. So instead of this, I created a new Class HTTPPost. This class now has the method that gets an NSDictionary passed and returns one. This works ALMOST. The problem I was now encountering is, that I couldn't really determine if the process was finished or not. So I started to create a new class called Globals and use global Variable loading. But the global variable is ALWAYS NO. So, what would be the best way to do this?
Here is my code:
This is where I check for the user and load it. resultDictionary is the NSDictionary where everything gets loaded in, but is always nil
[user loadModelFrom:[NSString stringWithFormat:#"WHERE facebookId='%#'", graphUser.id]];
NSLog(#"%#", user.resultDictionary);
if ( user.resultDictionary == nil ) {
NSLog(#"NIL");
} else {
NSLog(#"NOT NIL");
}
The problem now, is, that, since I'm sending an AsynchronousRequest, the resultDictionary is always nil. What I did before and worked was the following.
In my Model I had the HTTP Request and a variable named loading. Now I set loading to false until the response has been made into a NSDictionary
returnDict = [NSJSONSerialization JSONObjectWithData: [responseBody dataUsingEncoding:NSUTF8StringEncoding]
options: NSJSONReadingMutableContainers
error: &error];
But, then I had another problem. I had to do this in all my Models again... So I created a new Class that subclasses NSObject, that has the asynchronousRequest. This is the whole request
-(NSDictionary *)doHttpRequest:(NSDictionary *)postDict{
loading = NO;
__block NSDictionary *returnDict;
NSError *error;
NSString *jsonString;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:postDict
options:NSJSONWritingPrettyPrinted // Pass 0 if you don't care about the readability of the generated string
error:&error];
if (! jsonData) {
NSLog(#"Got an error: %#", error);
} else {
jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}
NSURL *aUrl = [NSURL URLWithString:#"http://xx.xx-xx.xx/xx.xx"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:aUrl
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
NSString *authStr = [NSString stringWithFormat:#"%#:%#", #"xx", #"xx"];
NSData *authData = [authStr dataUsingEncoding:NSASCIIStringEncoding];
NSString *authValue = [NSString stringWithFormat:#"Basic %#", [authData base64EncodedString]];
[request setValue:authValue forHTTPHeaderField:#"Authorization"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-type"];
[request setHTTPMethod:#"POST"];
[request setHTTPBody:[jsonString dataUsingEncoding:NSUTF8StringEncoding]];
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
NSString *responseBody = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
returnDict = [NSJSONSerialization JSONObjectWithData: [responseBody dataUsingEncoding:NSUTF8StringEncoding]
options: NSJSONReadingMutableContainers
error: &error];
}];
[queue waitUntilAllOperationsAreFinished];
loading = YES;
return returnDict;
}
As you can see I have now a variable called loading. It is a global variable. But somehow, the variable is always NO.
What would be the best way to do this? I hope I'm understandable, I'm new to Objective-C, and English isn't my native language.
UPDATE
I modified the code to look like a user provided here, but still not working!
HTTPPost.h
-(void)doHttpRequest:(NSDictionary *)postDict completion:(void(^)(NSDictionary *dict, NSError *error))completion {
__block NSDictionary *returnDict;
NSError *error;
NSString *jsonString;
NSString *authValue;
NSString *authStr;
NSData *jsonData;
NSData *authData;
NSURL *aUrl;
NSMutableURLRequest *request;
NSOperationQueue *queue;
jsonData = [NSJSONSerialization dataWithJSONObject:postDict
options:NSJSONWritingPrettyPrinted
error:&error];
if (! jsonData) {
NSLog(#"Got an error: %#", error);
} else {
jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
}
aUrl = [NSURL URLWithString:#"http://xx.xx-xx.com/xx.php"];
request = [NSMutableURLRequest requestWithURL:aUrl
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
queue = [[NSOperationQueue alloc] init];
authStr = [NSString stringWithFormat:#"%#:%#", #"xx", #"xx"];
authData = [authStr dataUsingEncoding:NSASCIIStringEncoding];
authValue = [NSString stringWithFormat:#"Basic %#", [authData base64EncodedString]];
[request setValue:authValue forHTTPHeaderField:#"Authorization"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-type"];
[request setHTTPMethod:#"POST"];
[request setHTTPBody:[jsonString dataUsingEncoding:NSUTF8StringEncoding]];
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
NSString *responseBody = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
returnDict = [NSJSONSerialization JSONObjectWithData: [responseBody dataUsingEncoding:NSUTF8StringEncoding]
options: NSJSONReadingMutableContainers
error: &error];
if ( completion ) {
completion(returnDict, error);
}
}];
}
//User.h
[_httpPost doHttpRequest:_dbDictionary completion:^(NSDictionary *dict, NSError *error) {
NSLog(#"completed") // NEVER GETS FIRED
}];
It seems that you're trying to take an asynchronous process (sendAsynchronousRequest) , and make it behave like a synchronous process (i.e. you appear to want to wait for it). You should not do that. You should to embrace the asynchronous patterns rather than fighting them.
The sendAsynchronousRequest method has a completion block that specifies what you want to do when the request is done. Do not try to put the code after the block and (try to) wait for the block to complete, but rather put any of your code that is dependent upon the completion of the network request inside the completion block, or have the completion block call your code.
A common way would be to give your own methods their own completion blocks and then call those blocks in the completionHandler of sendAsynchronousRequest, something like:
- (void)performHttpRequest:(NSDictionary *)postDict completion:(void (^)(NSDictionary *dictionary, NSError *error))completion
{
// prepare the request
// now issue the request
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
if (error) {
if (completion)
completion(data, error);
} else {
NSString *responseBody = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
returnDict = [NSJSONSerialization JSONObjectWithData:data
options: NSJSONReadingMutableContainers
error: &error];
if (completion)
completion(returnDict, error);
}];
}
Now, when you want to perform your request, you simply do:
[self performHttpRequest:someDictionary completion:^(NSDictionary *dictionary, NSError *error) {
if (error) {
// ok, handle the error here
} else {
// ok, use the `dictionary` results as you see fit here
}
];
Note, the method that calls this performHttpRequest (let's imagine you called it from loadModelFrom ) now behaves asynchronously, itself. So you might want to employ this completion-block pattern again, e.g. adding your own completion block parameter to loadModelFrom, and then invoke that block in the completion handler loadModelFrom passes to performHttpRequest.
But hopefully you get the idea: Never try to wait for a completion block, but rather just put inside that block anything you want it to do when its done. Whether you use AFNetworking (which I'd advise), or continue to use sendAsynchronousRequest, this is a very useful pattern with which you should become familiar.
Update:
The revised code sample (largely) works great for me. Seeing your revised question, a couple of observations:
I am not familiar with this base64EncodedString method. In iOS 7, there is the native base64EncodedStringWithOptions method (or for earlier iOS versions use base64Encoding). Or are you using a third party base-64 NSData category?
There's no point in creating jsonString, only to then convert it back to a NSData. Just use jsonData in your request.
The same is true with responseBody: Why convert to string only to convert back to NSData?
There's no point in having returnDict to be defined as __block outside the sendAsynchronousRequest block. Just define it inside that block and the __block qualifier is then no longer necessary.
Why create a NSOperationQueue for the completionHandler of sendAsynchronousRequest? Unless I'm doing something really slow that merits running on a background queue, I just use [NSOperationQueue mainQueue], because you invariably want to update the app's model or UI (or both), and you want to do that sort of stuff on the main queue.
The request still runs asynchronously but the queue parameter just specifies which queue the completion block will run on.
By the way, in sendAsynchronousRequest, you aren't checking to see if the request succeeded before proceeding with JSONObjectWithData. If the request failed, you could theoretically be losing the NSError object that it returned. You really should check to make sure the request succeeded before you try to parse it.
Likewise, when you originally dataWithJSONObject the parameters in postDict, you really should check for success, and if not, report the error and quit.
I notice that you're using the NSJSONReadingMutableContainers option. If you really need a mutable response, I'd suggest making that explicit in your block parameters (replacing all the NSDictionary references with NSMutableDictionary). I assume you don't really need it to be mutable, so I therefore recommend removing the NSJSONReadingMutableContainers option.
Likewise, when creating the JSON, you don't need to use the NSJSONWritingPrettyPrinted option. It only makes the request unnecessary larger.
Combining all of this, that yields:
-(void)performHttpRequest:(NSDictionary *)postDict completion:(void(^)(NSDictionary *dict, NSError *error))completion {
NSError *error;
NSString *authValue;
NSString *authStr;
NSData *jsonData;
NSData *authData;
NSURL *aUrl;
NSMutableURLRequest *request;
jsonData = [NSJSONSerialization dataWithJSONObject:postDict options:0 error:&error];
if (!jsonData) {
if (completion)
completion(nil, error);
return;
}
aUrl = [NSURL URLWithString:#"...."];
request = [NSMutableURLRequest requestWithURL:aUrl
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
authStr = [NSString stringWithFormat:#"%#:%#", #"xx", #"xx"];
authData = [authStr dataUsingEncoding:NSASCIIStringEncoding];
if ([authData respondsToSelector:#selector(base64EncodedStringWithOptions:)])
authValue = [NSString stringWithFormat:#"Basic %#", [authData base64EncodedStringWithOptions:0]];
else
authValue = [NSString stringWithFormat:#"Basic %#", [authData base64Encoding]]; // if only supporting iOS7+, you don't need this if-else logic and you can just use base64EncodedStringWithOptions
[request setValue:authValue forHTTPHeaderField:#"Authorization"];
[request setValue:#"application/json" forHTTPHeaderField:#"Content-type"];
[request setHTTPMethod:#"POST"];
[request setHTTPBody:jsonData];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if (!data) {
if (completion)
completion(nil, error);
return;
}
NSError *parseError = nil;
NSDictionary *returnDict = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
if (completion) {
completion(returnDict, parseError);
}
}];
}
And if this is being called from another method that needs to handle the fact that this is happening asynchronously, then it would employ a completion block pattern, too:
- (void)authenticateUser:(NSString *)userid password:(NSString *)password completion:(void (^)(BOOL success))completion
{
NSDictionary *dictionary = #{ ... };
[self performHttpRequest:dictionary completion:^(NSDictionary *dict, NSError *error) {
if (error) {
completion(NO);
return;
}
// now validate login by examining resulting dictionary
BOOL success = ...;
// and call this level's completion block
completion(success);
}];
}
Then the view controller might access that method with something like:
// maybe add UIActivityIndicatorView here
[self.userModel authenticateUser:self.userTextField.text password:self.passwordTextField.text completion:^(BOOL success) {
// remove UIActivityIndicatorView here
if (success) {
// do whatever you want if everything was successful, maybe segue to another view controller
} else {
// show the user an alert view, letting them know that authentication failed and let them try again
}
}];
After seeing you adding specific code to handle request and its responses, I would point out that you should try using AFNetworking. It abstracts out lots of boiler plate code.
As you mentioned, you are new to obj-c, it may take some time to understand AFNetworking but in long run, it will save you lots of headache. Plus it is one of the widely used open source for network related stuff.
I hope this would be helpful.
If you want to wait for a request, then you should not use sendAsynchronousRequest.
Use sendSynchonousRequest instead. That's where it's made for:
NSURLResponse *response;
NSError * error;
NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
But, the UI is blocked when the synchronous call is made. I doubt if that is what you want.
I am using AFNetworking, (AFHTTPRequestOperation) to make calls to the network and get the data back. I need to make use of the code in a for loop (enumeration of cards) to check for each card and get the data back, if the operation is successful, I get the information about the cards and if it fails, I should get an alert (using an alert view). The problem is I am getting multiple alerts if it fails (because it's inside a for loop and there can be a number of cards). How can I just show one alert only when it fails to connect to the network?
I know the operation is async, but can't get this to work.
Code below:-
- (void)verifyMobileDeviceStatus
{
[self fetchRequest];
[self.contentsArray enumerateObjectsUsingBlock:^(GCards *gCard, NSUInteger idx, BOOL * stop) {
NSURL *baseURL = nil;
baseURL = [NSURL URLWithString:BASE_URL_STRING];
NSString *soapBody = [NSString stringWithFormat:#"<?xml version=\"1.0\" encoding=\"utf-8\" standalone=\"yes\"?><soapenv:Envelope xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:soapenc=\"http://schemas.xmlsoap.org/soap/encoding/\" xmlns:soapenv=\"http://schemas.xmlsoap.org/soap/envelope/\"><soapenv:Header/><soapenv:Body><VerifyMobileDeviceStatus xmlns=\"http://tempuri.org/\"><Request><AuthToken>%#</AuthToken></Request></VerifyMobileDeviceStatus></soapenv:Body></soapenv:Envelope>", [gCard valueForKey:#"authToken"]];
NSLog(#" auth token =%#", [gCard valueForKey:#"authToken"]);
NSMutableURLRequest * request = [NSMutableURLRequest requestWithURL:baseURL];
NSString *msgLength = [NSString stringWithFormat:#"%d", [soapBody length]];
[request setHTTPMethod:#"POST"];
[request setHTTPBody:[soapBody dataUsingEncoding:NSUTF8StringEncoding]];
[request addValue: msgLength forHTTPHeaderField:#"Content-Length"];
[request addValue:#"http://tempuri.org/VerifyMobileDeviceStatus" forHTTPHeaderField:#"SOAPAction"];
[request addValue:#"text/xml; charset=utf-8" forHTTPHeaderField:#"Content-Type"];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"success: %#", operation.responseString);
NSString *xmlString = [operation responseString];
[parser setGCard:gCard];
[parser parseXML:xmlString];
if([gCard.merchantStatus isEqualToString:MERCHANT_STATUS_ACTIVE])
{
gCard.isPremiumAccount = [NSNumber numberWithInt:1];
}
else
{
gCard.isPremiumAccount = [NSNumber numberWithInt:0];
}
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
[parser.delegate verifyDeviceStatusParserDidFailWithError:#"Error"];
NSLog(#"error: %#", [error userInfo]);
}];
[operation start];
}];
}
- (void)verifyDeviceStatusParserDidFailWithError:(NSString *)error
{
NSString *errorString = [NSString stringWithFormat:#"Error =%#", [error description]];
NSLog(#"Error parsing XML: %#", errorString);
BlockAlertView* alert = [BlockAlertView alertWithTitle:#"Connection Failed" message:#"Connection to web service Failed. Please try again."];
[alert addButtonWithTitle:NSLocalizedString(#"OK", nil) block:^{ }];
[alert show];
[activityIndicator stopAnimating];
self.navigationController.view.userInteractionEnabled = YES;
}
It's showing the alert multiple times, if it fails and I need to show it only once.
Any help would be appreciated.
You need to make the alert view a property of the class, so.
1 - Declare a property (alert) of type BlockAlertView in the class that make the multiple requests (let's call it RequesterClass). This property will reference an unique alert view, which will be displayed only once.
2 - Put this 2 lines in the init method of the RequesterClass
_alert = [BlockAlertView alertWithTitle:#"Connection Failed" message:#"Connection to web service Failed. Please try again."];
[_alert addButtonWithTitle:NSLocalizedString(#"OK", nil) block:^{ }];
3 - Modify the verifyDeviceStatusParserDidFailWithError: as follows:
- (void)verifyDeviceStatusParserDidFailWithError:(NSString *)error
{
NSString *errorString = [NSString stringWithFormat:#"Error =%#", [error description]];
NSLog(#"Error parsing XML: %#", errorString);
if(!alert.visible)
{
[alert show];
}
[activityIndicator stopAnimating];
self.navigationController.view.userInteractionEnabled = YES;
}
Hope it helps!
The code is shown as below, I have a button once you click it activates timer and timer calls method every 4sec. However, sometimes 4 sec is not enough for server to return the data. However, increasing the timer value is not also good solution if server returns data in 1 sec and would not good for user to wait longer. I do not know what is best/optimal solution in this case.
-(IBAction)play:(id)sender{
timer=[NSTimer scheculedWith TimerInterval(4.0) target:(self)selector:#selector(httpRequest) userinfo:nil repeats:YES]
}
-(void)httpRequest{
_weak ASIHTTPRequest *request1 = [ASIHTTPRequest requestWithURL:url1];
[request1 setCompletionBlock:^{
NSString *responseString1 = [request1 responseString];
//dispatch_async(backgroundProcess1,^(void){
[self plotOverlay1:responseString1];
//});
}];
[request1 setFailedBlock:^{
NSError *error=[request1 error];
NSLog(#"Error: %#", error.localizedDescription);
}];
[request1 startAsynchronous];
}
If you just want the data to be updating continuously, consider calling -httpRequest again from within the completion block of the first request (and removing the timer). That way, you can be assured that the request will get performed again, but only after the first request finishes - and you can introduce a delay there, so you get something like "check again two seconds after the first check finishes."
This might look something like:
- (void)httpRequest {
__weak ASIHTTPRequest *req = [ASIHTTPRequest requestWithURL:url1];
[req setCompletionBlock:^{
NSString *resp = [req responseString];
[self plotOverlay1:resp];
[self httpRequest];
// or...
[self performSelector:#selector(httpRequest) withObject:nil afterDelay:2.0];
}];
/* snip fail block */
[req startAsynchronous];
}
Here i am trying to call my ASIHTTPRequest in a GCD. Sometimes the comletion blocks and failed blocks are not executing. What i want to do is, after this request finished, i have to use the returned data in a another ASIHTTPRequest. So how to improve this code:
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:url]];
[request setCompletionBlock:^{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
NSData *_responseData = [request responseData];
NSString *response = [[NSString alloc] initWithData:_responseData encoding:NSASCIIStringEncoding] ;
self.albumDic = [response JSONValue];
[response release];
dispatch_async(dispatch_get_main_queue(), ^{
[self GetDictionary:self.albumDic];
});
});
}];
[request setFailedBlock:^{
NSError *error = [request error];
NSLog(#"Error : %#", error.localizedDescription);
}];
[request startSynchronous];
Don't go that way. You're doing threading on threading (GCD uses threading and so does ASIHTTPRequest when used asynchronously).
Use ASINetworkQueue instead - read about it here
Here is a simple way you could use it:
- (void)addRequestsToNetworkQueue:(NSArray *)requests {
// Stop anything already in the queue before removing it
[[self networkQueue] cancelAllOperations];
// Creating a new queue each time we use it means we don't have to worry about clearing delegates or resetting progress tracking
[self setNetworkQueue:[ASINetworkQueue queue]];
[[self networkQueue] setDelegate:self];
[[self networkQueue] setRequestDidFinishSelector:#selector(requestFinished:)];
[[self networkQueue] setRequestDidFailSelector:#selector(requestFailed:)];
[[self networkQueue] setQueueDidFinishSelector:#selector(queueFinished:)];
//Add all requests to queue
for (ASIHTTPRequest *req in requests) {
[[self networkQueue] addOperation:req];
}
//Start queue
[[self networkQueue] go];
}
ASINetworkQueue provides many delegate methods (most are also customizable), so you can update the GUI when a request is finished and so forth. It is asynchronous, so GCD is unnecessary.