So i have this method in my app that returns BOOL if and update is available for my apps content
- (BOOL)isUpdateAvailable{
NSData *dataResponse=[NSData dataWithContentsOfURL:[NSURL URLWithString:#"url that returns json object"] ];
if(dataResponse!=nil){
NSError *error;
dicUpdates = [NSJSONSerialization JSONObjectWithData:dataResponse options:NSJSONReadingMutableContainers error:&error];
}
if(dicUpdates.count > 0) isUpdateAvailable = YES;
else isUpdateAvailable = NO;
return isUpdateAvailable;
}
I need a synchronous request for this, cause the next view controller will be dependent on the server response. However sometimes it takes a long time for the server to respond or the internet is really slow, i need to set a time out to prevent the app from 'being frozen'.
I previously used NSUrlconnection to accomplish this task, but it has been deprecated.
Also, I tried using NSURLSession, (been using it also to download updates in the background thread), but i just can figure out if it can be used for a synchronous request.
Any idea how to deal with this? i just need a synchronous method that returns a BOOL. Best regards.
We have to use NSURLRequest in NSURLSession to set timeout interval.
Check below code:
- (BOOL)isUpdateAvailable{
NSURLSession *session = [NSURLSession sharedSession];
[[session dataTaskWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:#"url that returns json object"] cachePolicy:NSURLRequestReloadIgnoringCacheData timeoutInterval:4]//timeout
completionHandler:^(NSData *dataResponse,
NSURLResponse *response,
NSError *error) {
// handle response
if(dataResponse!=nil){
NSError *error;
dicUpdates = [NSJSONSerialization JSONObjectWithData:dataResponse options:NSJSONReadingMutableContainers error:&error];
}
if(dicUpdates.count > 0) isUpdateAvailable = YES;
else isUpdateAvailable = NO;
return isUpdateAvailable;
}] resume];
}
Related
In my application, I am performing POST using NSURLSession.
Steps followed:
Setting Header
Setting HTTPBody
Making POST request using NSURLSession.
The code is:
NSDictionary *parameters = #{ #"searchTerm": #"shampoo", #"sort": #"Most Reviewed" };
NSError *error = nil;
NSData *postData = [NSJSONSerialization dataWithJSONObject:parameters options:NSJSONWritingPrettyPrinted error:&error];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:#"SomeURL"]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:10.0];
[request setHTTPMethod:#"POST"];
[request setAllHTTPHeaderFields:headers];
request.HTTPBody = postData;
NSURLSession *session = [NSURLSession sharedSession];
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
if (error) {
NSLog(#"%#", error);
} else {
NSLog(#"Pass");
}
}];
[dataTask resume];
Now in custom NSURLProtocol class:
(BOOL)canInitWithRequest:(NSURLRequest *)request {
if ([request.HTTPMethod isEqualToString:#"POST"]) {
//here request.HTTPMethod is coming nil
//Whereas my requirement is to get request.HTTPMethod which got request parameter.
return YES;
}
return NO;
}
Thanks in advance.
IIRC, body data objects get transparently converted into streaming-style bodies by the URL loading system before they reach you. If you need to read the data:
Open the HTTPBodyStream object
Read the body data from it
There is one caveat: the stream may not be rewindable, so don't pass that request object on to any other code that would need to access the body afterwards. Unfortunately, there is no mechanism for requesting a new body stream, either (see the README file from the CustomHTTPProtocol sample code project on Apple's website for other limitations).
I trying to implement Load image asynchronously.
NSURL *url = [NSURL URLWithString:_posterImg];
NSURLRequest* request = [NSURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse * response,
NSData * data,
NSError * error) {
if (!error){
UIImage *getImg = [[UIImage alloc] initWithData:data];
// do whatever you want with image
}
}];
But when i put this code, getImg will get warning "Unused Variable". i had check "response", "data" and "error", it all look fine but the getImg is NIL. is that i had write any thing wrong? thanks.
The affected variable is response. Although you use data and error, response is only declared as a parameter but nowhere used in your completion handler!
NSURL *url = [NSURL URLWithString:_posterImg];
NSURLRequest* request = [NSURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse * response,
NSData * data,
NSError * error) {
NSString *errorMsg = nil;
UIImage *getImg = nil;
if (!error){
getImg = [[UIImage alloc] initWithData:data];
}
else
{
errorMsg = [NSString stringWithFormat:#"Failed to load image. Error Message: %#", [error localizedString]];
}
[self handleImageRequestWithResponse:response image:getImg andErrorMessage:errorMsg];
}];
// Image hasn't load yet here since the request is asynchronously!
//if(getImg != nil && errorMsg == nil)
// NSLog(#"Image is available!");
//else
// NSLog(#"Loading the image asynchronously failed! %#", errorMsg);
// In addition now provide the following method.
- (void) handleImageRequestWithResponse:(NSURLResponse*)response image:(UIImage*)img andErrorMessage:(NSString*)err
{
if(img!= nil && err == nil)
NSLog(#"Image is available!");
else
NSLog(#"Loading the image asynchronously failed! %#", err);
// Handle image
};
EDIT: My bad! Since the code executes asynchronously getImg was of course nil when you checked as before
EDIT:
Using NSData dataWithContentsOfURL is synchronous,i.e. if executed on the main thread your application is blocked.
See this official documentation: https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSData_Class/Reference/Reference.html#//apple_ref/occ/clm/NSData/dataWithContentsOfURL:
Most important:
Important: Do not use this synchronous method to request network-based URLs. For network-based URLs, this method can block the current thread for tens of seconds on a slow network, resulting in a poor user experience, and in iOS, may cause your app to be terminated.
Going for a completionHandler and a handler method called after the requested raw data has been handled/prepared is better for your performance and does not violate the official recommendation!
I'm working with TWrequest to display my twitter lists in a tableview. The following code works. The problem is it is very slow to update the table. I am NSlogging the request response (which happens very quickly), I am also looping through each list and adding the list 'name' to an array (which again, happens very quickly <1s). But for some inexplicable reason, the table takes roughly a further 4 seconds or so to update.
Why is this taking so long for the table to reload? The problem is not parsing the response (because I can see with nslog this happens pretty quick), it's taking a long time to display in the table? Help very much appreciated!
-(IBAction)getLists{
// First, we need to obtain the account instance for the user's Twitter account
ACAccountStore *store = [[ACAccountStore alloc] init];
ACAccountType *twitterAccountType = [store accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierTwitter];
// Request permission from the user to access the available Twitter accounts
[store requestAccessToAccountsWithType:twitterAccountType withCompletionHandler:^(BOOL granted, NSError *error) {
if (!granted) {
// The user rejected your request
NSLog(#"User rejected access to the account.");
}
else {
// Grab the available accounts
twitterAccounts = [store accountsWithAccountType:twitterAccountType];
if ([twitterAccounts count] > 0) {
// Use the first account for simplicity
ACAccount *account = [twitterAccounts objectAtIndex:0];
// Now make an authenticated request to our endpoint
NSMutableDictionary *params = [[NSMutableDictionary alloc] init];
//[params setObject:#"1" forKey:#"include_entities"];
// The endpoint that we wish to call
NSURL *url = [NSURL URLWithString:#"http://api.twitter.com/1.1/lists/list.json"];
// Build the request with our parameter
TWRequest *request = [[TWRequest alloc] initWithURL:url parameters:params requestMethod:TWRequestMethodGET];
// Attach the account object to this request
[request setAccount:account];
[request performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) {
if (!responseData) {
// inspect the contents of error
NSLog(#"error = %#", error);
}
else {
NSError *jsonError;
NSArray *timeline = [NSJSONSerialization JSONObjectWithData:responseData options:NSJSONReadingMutableLeaves error:&jsonError];
if (timeline) {
// at this point, we have an object that we can parse
NSLog(#"timeline = %#", timeline);
for (NSDictionary *element in timeline) {
NSString *listName = [element valueForKey:#"name"];
[listsArray addObject:listName];
}
[listsTable reloadData];
}
else {
// inspect the contents of jsonError
NSLog(#"jsonerror = %#", jsonError);
}
}
}];
}
}
}];
}
Sorry, just came across this post. If you haven't found a solution yet, hopefully this will help.
I believe that performRequestWithHandler can be called on any thread, so UI changes should be dispatched to the main thread.
dispatch_async(dispatch_get_main_queue(), ^{
//update UI here
});
Or in the case of reloading table data you can use:
[self.tableView performSelectorOnMainThread:#selector(reloadData) withObject:nil waitUntilDone:NO];
I know its something to do with locks or dispatch groups, but I just cant seem to code it...
I need to know if the address was a valid address before leaving the method. Currently the thread just overruns and returns TRUE. I've tried locks, dispatchers the works but can't seem to get it correct. Any help appreciated:
- (BOOL) checkAddressIsReal
{
__block BOOL result = TRUE;
// Lets Build the address
NSString *location = [NSString stringWithFormat:#" %# %#, %#, %#, %#", streetNumberText.text, streetNameText.text, townNameText.text, cityNameText.text, countryNameText.text];
// Put a pin on it if it is valid
CLGeocoder *geocoder = [[CLGeocoder alloc] init];
[geocoder geocodeAddressString:location
completionHandler:^(NSArray* placemarks, NSError* error) {
result = [placemarks count] != 0;
}];
return result;
}
The documentation says that CLGeocoder calls the completionHandler on the main thread. Since you are probably also calling your method from the main thread it cannot wait for the geocoder's answer without giving it the opportunity to deliver the result.
That would be done by polling the runloop, using some API as -[NSRunLoop runMode:beforeDate:].
The disadvantage is that depending on the mode this will also deliver events and fire timers while waiting for the result.
Just use block as parameter:
- (void) checkAddressIsRealWithComplectionHandler:(void (^)(BOOL result))complectionHandler
{
__block BOOL result = TRUE;
// Lets Build the address
NSString *location = [NSString stringWithFormat:#" %# %#, %#, %#, %#", streetNumberText.text, streetNameText.text, townNameText.text, cityNameText.text, countryNameText.text];
// Put a pin on it if it is valid
CLGeocoder *geocoder = [[CLGeocoder alloc] init];
[geocoder geocodeAddressString:location
completionHandler:^(NSArray* placemarks, NSError* error) {
result = [placemarks count] != 0;
complectionHandler(result);
}];
}
CD's been an enormous learning curve for me and there's still a bit for me to go, but any help on the following could enable me to lift the current weight on my shoulders!
I'm trying to write a method that implements a "Save As.." for the user in my CD app.
So far I've got:
[saveAsPanel beginSheetModalForWindow:window completionHandler:^(NSInteger userResult)
{
if (userResult == NSOKButton) {
NSPersistentStoreCoordinator *psc = [self persistentStoreCoordinator];
NSURL *oldURL = [self URLOfInternalStore]; //returns the current store's URL
NSURL *newURL = [saveAsPanel URL];
NSError *error = nil;
NSPersistentStore *oldStore = [psc persistentStoreForURL:oldURL];
NSPersistentStore *sqLiteStore = [psc migratePersistentStore:oldStore
toURL:newURL
options:nil
withType:NSXMLStoreType
error:&error];
}
}];
Unfortunately, I just get the error:
Object's persistent store is not reachable from this NSManagedObjectContext's coordinator.
Should I 'remove' and then 'addPersistentStore...' to update it to the new URL? The doc's seem to suggest that all will be handled with in the 'migrate' method.
Thanks in advance!
Edit:
Ok, well, I've come up with my own 'dirty' method. I can imagine that this isn't an approved way of doing things, but there's no error thrown up and the app works as expected at all times (not often I can say that, either!):
-(IBAction)saveAsAction:(id)sender
{
NSSavePanel *saveAsPanel = [NSSavePanel savePanel];
[saveAsPanel beginSheetModalForWindow:window completionHandler:^(NSInteger userResult)
{
if (userResult == NSOKButton) {
[self saveAction:#"saveAsCalling"];
NSURL *newURL = [saveAsPanel URL];
NSError *error = nil;
[[NSFileManager defaultManager] copyItemAtURL:[NSURL fileURLWithPath:internalStore] toURL:newURL error:&error];
//internalStore is a hard-wired NSString that holds the path to the bundle's database
}
}];
}
-(IBAction)loadAction:(id)sender
{
NSOpenPanel *loadPanel = [NSOpenPanel openPanel];
[loadPanel beginSheetModalForWindow:window completionHandler:^(NSInteger userResult)
{
if (userResult == NSOKButton) {
[self saveAction:#"loadCalling"];
NSURL *newURL = [loadPanel URL];
NSURL *oldURL = [NSURL fileURLWithPath:internalStore];
NSError *error = nil;
NSPersistentStoreCoordinator *psc = [SELF_MOC persistentStoreCoordinator];
[psc removePersistentStore:[[self persistentStoreCoordinator] persistentStoreForURL:oldURL] error:&error];
[psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:newURL options:nil error:&error];
[[NSFileManager defaultManager] removeItemAtURL:oldURL error:&error];
[[NSFileManager defaultManager] copyItemAtURL:newURL toURL:oldURL error:&error];
[psc removePersistentStore:[[self persistentStoreCoordinator] persistentStoreForURL:newURL] error:&error];
[psc addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:oldURL options:nil error:&error];
}
}];
}
The basic reasoning is this: to do a 'SaveAs...' I simply copy out the SQLLite store file in the mainBundle to wherever the user selects and rename it to what they want - as per TechZen's suggestion.
To do a 'Load' then I first removePersistentStore from the bundle's file, add the one that the user's just chosen. Delete the bundle store (which in theory isn't now being used) and then copy the user's choice back into the bundle. Finally, the two operations of remove and addPersistentStore are performed to point the app back to it's bundle's file which is now the user's choice.
Hope that makes sense. If anyone has any thoughts on just how unprofessional a methodology this is then please - be kind as I'm fairly new - let me know. I can't find anything that is more elegant.
I know Apple don't like you using removePersistentStore and addPersistentStore but, as I say no errors are reported (in my actual code I scattered NSLog lines throughout to report what error is holding).
You only use a SaveAs... in a document based app. If you use Core Data as your model, you need to use NSPersistentDocument to save your data. It provide the SaveAs... functionality you seek.
Straight Core Data is used for more database-like apps in which the entire app operates from one data set (more or less.)