I am a beginner and trying hands on Json parsing. I am successfully parsing the data I need. But the problem is I don't know how to save and use that value in another function.
For now, I am doing everything in view controller.m for the sake of simplicity. Meaning all my code is in viewcontroller.m
Will later use a separate class.
I have a button and a label on my storyboard. So I am trying to fetch a value from Json .api and want to show that value in label. When user presses button, the parsing is triggered. As u can c below.
- (IBAction)btnPressed:(id)sender {
NSURL *url=[NSURL URLWithString:#"http:........myweb"];
NSURLRequest *request=[NSURLRequest requestWithURL:url];
connection=[NSURLConnection connectionWithRequest:request delegate:self];
if(connection)
{
webData=[[NSMutableData alloc]init];
self.outputLbl.text = [NSString stringWithFormat:#"%#", goldRate];
}
but the value printed in the label is null. when we fetch info and display in tableviews, we set delegates. but for a label we don't set delegate. So I am confused what the problem is? have i forgot to set a delegate or am i passing data incorrectly. pls the function below.
-(void) connectionDidFinishLoading:(NSURLConnection *)connection{
NSDictionary *allDataDictionary=[NSJSONSerialization JSONObjectWithData:webData options:0 error:nil];
NSArray *myDataArray=[allDataDictionary objectForKey:#"data"];
NSArray *myGoldArray=[myDataArray objectAtIndex:0];
goldRate=[[myGoldArray objectAtIndex:1] stringValue];
}
I have made this goldRate a global variable. But when I debug my program. In the connectionDidFinishLoading, the goldRate value is absolutely what I want. But when I try to use this goldRate in btnPressed function, in that function the value is null.
Please help.
When the button is pressed, you initiate a load. When the load completes (some time later) the connectionDidFinishLoading: method is called. But until that happens, "goldRate" will be nil (because it is not yet initialized).
Set the label in the connectionDidFinishLoading: instead of where you have it, and the value will show up.
Related
In my app I'm populating a tableview with an array of jobs that I have from a web service. Every job has a specific job ID that I can grab. Now when someone taps a job from the table view, they are brought to the DetailsViewController which displays all the information about that job. So far, my code looks like this to set the job title in the details view controller:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"next"])
{
NSString *theCorrectUrlString = [NSString stringWithFormat:#"%#", theUrlString];
NSURL *url = [NSURL URLWithString:theCorrectUrlString];
NSData *data = [NSData dataWithContentsOfURL:url];
NSError *error;
NSMutableArray *jobsCallArray = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
for (NSDictionary *theJob in jobsCallArray)
{
DetailsViewController *detailVC = (DetailsViewController*)segue.destinationViewController;
NSString *jobPosTitle = theJob[#"position_title"];
[detailVC setJobTitleString:jobPosTitle];
}
}
}
This code however gives me the same job title for every cell. I want to know how I can get the specific job chosen in my table view, and show all of its details on one page.
All help is appreciated, thanks in advance.
Your code doesn't make much sense. In this little fragment you're iterating through the array, and you're calling setJobTitleString for each object, but obviously whatever this setJobTitleString method does, the value is being overwritten and you only see the last value.
for (NSDictionary *theJob in jobsCallArray)
{
DetailsViewController *detailVC = (DetailsViewController*)segue.destinationViewController;
NSString *jobPosTitle = theJob[#"position_title"];
[detailVC setJobTitleString:jobPosTitle];
}
I can't really tell how to solve this because I don't know what you're trying to do. Retrieving data with dataWithContentsOfURL inside prepareForSegue is weird, especially because you're retrieving all data, but apparently you only want to show the details for one item.
I have a lot of classes which are sending requests and finally it all comes to SplitViewController. In the SplitUIviewclass I have to long poll and write the data in a table view. The long polling is done in the background thread, so I have declared a variable in app delegate, but when it comes to that it is nil. And the problem is whenever I try to access the NSMutablearray through the appdelegate, its coming as nil and the array is being released. My code for long polling is
- (void) longPoll {
#autoreleasePool
{
//compose the request
NSError* error = nil;
NSURLResponse* response = nil;
NSURL* requestUrl = [NSURL URLWithString:#"http://www.example.com/pollUrl"];
NSURLRequest* request = [NSURLRequest requestWithURL:requestUrl];
//send the request (will block until a response comes back)
NSData* responseData = [NSURLConnection sendSynchronousRequest:request
returningResponse:&response error:&error];
//pass the response on to the handler (can also check for errors here, if you want)
[self performSelectorOnMainThread:#selector(dataReceived:)
withObject:responseData waitUntilDone:YES];
}
//send the next poll request
[self performSelectorInBackground:#selector(longPoll) withObject: nil];
}
- (void) startPoll {
[self performSelectorInBackground:#selector(longPoll) withObject: nil];
}
- (void) dataReceived: (NSData*) theData {
//i write data received here to app delegate table
}
If I call any other method in my SplitView class from data received, I'm losing control, also I cannot print my app delegate values in data received or the variables being released, I cannot call reload table or any other method from here.
Cant you set your properties in your ViewControllers as strong/retain like so
property (strong,retain) NSMutableArray *myData;
BTW, I learned a moment ago that it is bad practise to use your AppDelegate as a storage place for global containers. The ApplicationDelegate is a place for application delegate methods and for the initial setup of the foundation of your app; such as setting up the navigationController.
So consider storing your data in the appropriate place, perhaps core data or something else.
I've been stuck on this for approximately two weeks. I hate posting things that have been asked a lot but I really have gone through them all.
I used Ray Wenderlich's tutorial for saving data in an iPhone app.
http://www.raywenderlich.com/tutorials
So that is the setup I have going on in my app. I'm saving very simple objects. My Card object consists of a name, type, and image. That's all. So the tutorial is quite close to mine. Which is making this more frustrating.
The thing is, I have some NSLog statements in there for loading. I have it displaying the folder it's using to load and what objects it does load. Right now it is displaying this.
Loading cards from /Users/zach/Library/Application Support/iPhone Simulator/7.0.3-64/Applications/E3DB01FD-A37E-4A69-840B-43830F2BDE2C/Library/Private Documents
2013-11-04 00:02:50.073 CardMinder[84170:a0b] ()
So it seems to be trying to load them, but there's nothing there to load. Here is my function to save data.
- (void)saveData {
if (_data == nil) return;
[self createDataPath];
NSString *dataPath = [_docPath stringByAppendingPathComponent:kDataFile];
NSMutableData *data = [[NSMutableData alloc] init];
NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
[archiver encodeObject:_data forKey:kDataKey];
[archiver finishEncoding];
NSLog(#"%#",dataPath);
NSLog(#"%#",data);
[data writeToFile:dataPath atomically:YES];
}
Which is really just what's posted in that tutorial. I know if you feel generous enough to help me out i'll have to post some more code but I don't want to flood the post with useless stuff so just let me know and i'll get it out here.
I really appreciate anyone that can help, I have recently entered the desperation state and need help.
Thanks
UPDATE
NSError *error;
[data writeToFile:dataPath options:NSDataWritingAtomic error:&error];
NSLog(#"error: %#", error.localizedFailureReason);
These are the methods for the CardData class. I'm doing the name, type, and a bool here.
- (void)encodeWithCoder:(NSCoder *)aCoder
{
[aCoder encodeObject:_name forKey:kNameKey];
[aCoder encodeObject:_cardType forKey:kTypeKey];
[aCoder encodeBool:_checkedOut forKey:kOutKey];
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
NSString *name = [aDecoder decodeObjectForKey:kNameKey];
NSString *cardType = [aDecoder decodeObjectForKey:kTypeKey];
BOOL checkedOut = [aDecoder decodeBoolForKey:kOutKey];
return [self initWithName:name cardType:cardType _Bool:checkedOut];
}
UPDATE 2
I just put some more NSLog statements in and I found out that when I press the "Save card" button in my app, it doesn't seem to execute the saveData function at all. I have log statements galore in that saveData function and when I click the saveCard button it doesn't show any of those logs. Why would that be happening?
This is my saveButton code.
- (IBAction)saveNewCard:(id)sender
{
NSString *cardName = self.nameField.text;
_cardDoc.data.name = cardName;
CardDoc *newCard = [[CardDoc alloc] initWithName:cardName cardType:cardTypeString _Bool:NO image:chosenIcon];
[_cardDoc saveData];
NSLog(#"Card save button pressed!");
CardViewController *cardViewController = (CardViewController *)[self.navigationController.viewControllers objectAtIndex:self.navigationController.viewControllers.count-2];
[cardViewController.cards addObject:newCard];
[self.navigationController popToRootViewControllerAnimated:YES];
}
You should use writeToFile:options:error: instead of writeToFile:atomically:; that will give you an error message that should prove helpful. (The equivalent to atomically:YES is the option constant NSDataWritingAtomic.) Make sure you're getting back a return value of YES; if not, the error should be set.
If you're getting a value of NO but the error is not set, it means you're messaging nil. A quirk of Objective-C is that messaging nil is completely valid. If the method is defined to return something, you'll even get a result: 0 or equivalent (NO, nil, etc.)
In this case, you're messaging _cardDoc. There's no return result to detect. This is a bit harder to defensively code around, but [_cardDoc saveData] is actually [nil saveData]. The debugger will just breeze past the line.
Generally, if something absolutely should not be nil, you can use NSAssert:
NSAssert(_cardData, #"_cardData should not be nil");
[_cardData saveData];
But use this sparingly; you'll probably come to usually appreciate this behaviour.
A few things.
Post the results of your log statements so we know what you are seeing.
In order for your approach to work, your _data object needs to conform to the NSCoding protocol. That means you need to add the protocol declaration to your interface, and implement the methods encodeWithCoder and initWithCoder.
In those methods you need to save all the state data for your object / load the state back into your object.
Those methods are the most likely source of problems with your code. Post those methods if you need help with them, and walk though them in the debugger.
You might also look at the NSKeyedArchvier class method archivedDataWithRootObject. That method takes an object and encodes it into an NSData object in one step. The method archiveRootObject:toFile: take it a step further, and writes the data directly to a file for you.
NSKeyedUnarchiver has the corresponding methods unarchiveObjectWithData and unarchiveObjectWithFile to recreate your object from data/a file.
I've looked around a lot and cant seem to find a proper answer for my problem. As of now I have a network engine and I delegate into that from each of the view controllers to perform my network activity.
For example, to get user details I have a method like this:
- (void) getUserDetailsWithUserId:(NSString*) userId
{
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:#"%#Details", kServerAddress]]];
request.HTTPMethod = #"POST";
NSString *stringData = [NSString stringWithFormat:#"%#%#", kUserId, userId];
NSData *requestBodyData = [stringData dataUsingEncoding:NSUTF8StringEncoding];
request.HTTPBody = requestBodyData;
NSURLConnection *conn = [[NSURLConnection alloc] init];
[conn setTag:kGetUserInfoConnection];
(void)[conn initWithRequest:request delegate:self];
}
And when I get the data in connectionDidFinishLoading, I receive the data in a NSDictionary and based on the tag I've set for the connection, I transfer the data to the required NSDictionary.
This is working fine. But now I require two requests going from the same view controller. So when I do this, the data is getting mixed up. Say I have a connection for search being implemented, the data from the user details may come in when I do a search. The data is not being assigned to the right NSDictionary based on the switch I'm doing inside connectionDidFinishLoading. I'm using a single delegate for the entire network engine.
I'm new to NSURLConnection, should I setup a queue or something? Please help.
EDIT
Here's the part where I receive data in the connectionDidFinishLoading:
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
if ([connection.tag integerValue] == kGetUserDetails)
networkDataSource.userData = self.jsonDetails;
if ([connection.tag integerValue] == kSearchConnection)
networkDataSource.searchData = self.jsonDetails;
}
and after this I have a switch case that calls the required delegate for the required view controller.
Anil here you need to identify for which request you got the data,
simplest way to check it is as below,
- (void)connectionDidFinishLoading:(NSURLConnection *)conn
{
// Check URL value for request, url for search and user details will be different, put if condition as per your need.
conn.currentRequest.URL
}
Try using conn.originalRequest.URL it will give original request.
You can do in many ways to accomplish your task as mentioned by others and it will solve your problem . But if you have many more connections , you need to change your approach.
You can cretae a subclass of NSOperation class. Provide all the required data, like url or any other any informmation you want to get back when task get accomplish , by passing a dictionary or data model to that class.
In Nsoperation class ovewrite 'main' method and start connection in that method ie put your all NSURRequest statements in that method. send a call back when download finish along with that info dict.
Points to be keep in mind: Create separte instance of thet operation class for evey download, and call its 'start method'.
It will look something like :
[self setDownloadOperationObj:[[DownloadFileOperation alloc] initWithData:metadataDict]];
[_downloadOperationObj setDelegate:self];
[_downloadOperationObj setSelectorForUpdateComplete:#selector(callBackForDownloadComplete)];
[_downloadOperationObj setQueuePriority:NSOperationQueuePriorityVeryHigh];
[_downloadOperationObj start];
metaDict will contain your user info.
In DownloadFileOperation class you will overwrite 'main' method like :
- (void)main {
// a lengthy operation
#autoreleasepool
{
if(self.isCancelled)
return;
// //You url connection code
}
}
You can add that operation to a NSOperationQueue if you want. You just need to add the operation to NSOperationQueue and it will call its start method.
Declare two NSURLConnection variables in the .h file.
NSURLConnection *conn1;
NSURLConnection *conn2;
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
if(connection == conn1){
}
else if(connection == conn2){
}
}
I have a function which makes GET request to the server. It works fine but for some reason it's called twice. I call function when a button is pressed.
This is function code:
-(void) GETasync: (NSString *) path{
receivedData = [[NSMutableData alloc] init];
NSURLRequest *request=[NSURLRequest requestWithURL:
[NSURL URLWithString: path]
cachePolicy:NSURLRequestReloadIgnoringLocalCacheData
timeoutInterval:60.0];
NSHTTPURLResponse * response;
NSError * error;
NSData * data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
NSLog(#"data received");
}
So I see in output:
2012-03-07 16:36:41.509 KW2[24136:bf03] data received
2012-03-07 16:36:41.694 KW2[24136:bf03] data received
I also have a function for POST request and it's the same trouble with it.
I am assuming that you are printing out that log within your delegate method connection:didReceiveData:. That method can be called multiple times for one single connection - in fact it is commonly called at least twice.
From the documentation:
The delegate is periodically sent connection:didReceiveData: messages as the data is received. The delegate implementation is responsible for storing the newly received data.
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// Append the new data to receivedData.
// receivedData is an instance variable declared elsewhere.
[receivedData appendData:data];
}
EDIT: I see that in your latest edits you have added that logging information (or maybe I did not see it right away - shame on me).
Are you possibly calling that method by a notification handler? If so, have you possibly double-registered for that notification -> hence your handler is invoked twice.
The problem was just in that I wired IBOutlets from File'Owner and First Responder to buttons in IB.
After removing wires from File's Owner, the method started to be called only one time.
Also make sure to check the IBAction connections for your button in Interface Builder. If you copy and paste buttons in IB, you can end up having 2 or more identical IBAction connections for a button, which would cause the method to be executed twice with just one button click.