I am new to iphone development. numberOfRowsInSection method of UITableViewController executed before parsing the XML node so that this method return value as zero, but this method should be return value of number of rows with data.
please help me
thanks.
After parsing of your XML data is finished call [myTable reloadData]; - it will force your UITableView to reload the data shown and thus all necessary methods (including numberOfRowsInSection) to get called.
I've had a similar problem before, and it was because I was passing the array/dictionary to the controller from the appdelegate. Unfortunately, after the app delegate went out of scope, the array was lost.
Try doing an array copy,
NSArray data = [NSArray arrayWithArray: passedInArray];
Sorry, don't have my trusty macbook on me to check the code, but you get the drift.
I solved this problem via made connection between tableView reference and file owner in interface builder.
Related
I have a UIViewController that contains a UITableView.
I'm trying to fill this table with data parsed from an XML file.
The first time the TableView loads the data isn't available just yet.
What would be the best way to reload this view?
I tried to do a self.TableView reloadData after the parsing finished.
Unfortunately the NSMutableArray holding the parse result getting reset during reloadData.
The array is set at the UIVivewController.
Should I set the NSMutablearray as a global variable?
THanks a bunch
The array should be an ivar (instance variable) of the view controller containing the UITableView. When you are done parsing the ivar should be populated with the data and you should be able to populate the UITableView with no problem using [self.TableView reloadData]. Make sure you are not removing all objects or re-initializing the array in any of the delegate or datasource callbacks.
Don't make it global, make it an instance variable. As in:
#interface MyViewController : UIViewController {
NSMutableArray* parsedDataArray; //declare the array here
}
#end
But beyond that, yes, calling reloadData after the parsing finishes is reasonable. Just fix the code to not reset the parse results when reloadData is called.
Yes, take that NSMutableArray as a global for that controller file.
Be sure u are getting value in NSMutableArray in the controller which holds table view.
simply reload table.
Regards,
Shyam
I'm new, but I read a lot about memory management, and really tried to find the answer myself.
It sounds so basic and yet I apparently don't get it.
I have a NSMutableArray as property in .h:
#property (nonatomic, retain) NSMutableArray *documentListArray;
I synthesize it and release it in (void) dealloc.
To populate the array, I have a method - (void)updateRecordList and in there:
self.documentListArray=[DocumentDatabase getDocumentListSortedByDate];
EDIT:next line:
[[self recordListTableView] reloadData];
where DocumentDatabase is a different class with the class methods getDocumentListSortedByDate and getDocumentList.
Here is what is happening in getDocumentListSortedByDate:
NSMutableArray *returnArray = [DocumentDatabase getDocumentList];
//sorting...
NSLog("array count:%i",[returnArray count]); //returns correct numbers first and second time
return returnArray;
and in getDocumentList
NSMutableArray *returnArray = [NSMutableArray arrayWithCapacity:files.count];
//add file data to array...
return returnArray;
This works the first time I call updateRecordList, but after adding a file and calling updateRecordList a second time, it crashes with (using NSZombies):
* -[NSCFNumber dealloc]: message sent to deallocated instance 0x7504c90.
With a lot of logging I narrowed the problem down to the line above in updateRecordList and it works if I change it to:
self.documentListArray=[[DocumentDatabase getDocumentListSortedByDate] retain];
My conclusion is that the array down in getDocumentList has been autoreleased before it arrives. So my questions are:
1. Why do I have to retain it there? Shouldn't that happen by itself by declaring the property (retain)?
Or, in other words, why is the array autoreleased too early (assuming this is what is happening)?
2. When I assign a new array to self.documentListArray, is the old array automatically released? If I try to release it myself before getting a new documentList, it crashes too.
Thanks in advance for any reply.
EDIT:
Maybe I'm an idiot: I failed to mention that documentListArray is the data source for an UITableView (see the added line on top). I suspect that I am doing something wrong with populating the table view, and the array gets retained...? It does however crash on assigning the property, not on reloadData.
I go back to study if I use the UITableViewDataSource protocol properly. Thanks to everybody, your answers brought me hopefully on the right track. Will update when solved.
EDIT2:
It works now without retaining, and I think I understand why: I debugged extensively and found that Objects contained in Objects added to the array where nil. Particularly, deep down in encodeWithCoder I did not use "self" when assigning values. When decoding, those values where nil. Since I changed that, it seems to work.
I suspect that not assigning the new array caused the crash, but the TableView which would read the new array-even before I call reloadData. Which would lead back to Davids question of synchroneous access. Thank you all for your help.
The code you've shown it appears correct; it should not be necessary (or correct) to call retain yourself, as long as you are assigning the value to a property with retain semantics before the autorelease pool is drained. Are all the calls (getDocumentListSortedByDate, getDocumentList) happening synchronously, or are you doing any of this in the background? Double-check that you're assigning using the "self." ("self.documentListArray =") instead of just assigning directly to the instance var ("documentListArray ="); if you omit the "self.", the setter is bypassed.
No, don't free the old value before assigning; that's the setter's job.
Hi i have found a problem with my DataSource of my UITableView.
Each time i try to fill the NSMutableArrayData in the method "addDataSection", the whole data-Array is set to the current Names-Array.
It all seems to work, until i write the Names into the Array and invoke [Names removeAllObjects]. Even in the method "addDataSection" my Names Array seems to be correct,
so i maybe have a problem with a memory leak?
This ist the Implementation of the init method in the datasource-object (calls addDataSection):
-> watch the code below
has anyone ever seen problems like this occur in objective c?
There are tons of leaks in your code. Here are some:
tempNames
currentPhoneNumber
currentEmail
tempDict
Also
[Names init];
Never ever send init to an object except straight after alloc.
You don't release tempDict.
And as says Ahmet, what is the [Names init] ?
I am stuck in a strange situation , i am getting data from the website using XML files and i am filling an Array (NSMutableArray Type) that i later use to display the data on Table View. The problem is that functions related to UITableView are called earlier and at that time the Array is not filled, this cause the program to crash. When this function is executed arrayData is empty and count functions returns nothing. Is there any way that i call NSXMLParser functions earlier than the UITableView functions.
-(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
return [arrayData count];
}
Thanks,
Taimur
The array would return 0 if it existed but without containing any objects - so the app shouldn't crash. This means your array has not been initialized yet. You have propably added a pointer to your array as an instance variable and maybe as property, but you still need to create the actual object towards which that pointer should point.
So, if we're dealing with a property of a viewcontroller subclass here, add something like this to your viewDidLoad method:
NSMutableArray *newArray = [[NSMutableArray alloc] init];
self.arrayData = newArray;
[newArray release];
Your situation is not strange at all - it is extremely common when developing apps with asynchronous data loading requirements.
NSXMLParser is a SAX (event-driven) parser - it will parse data when the data is available. It is up to you when you choose to display your table, but obviously if you try to display it before the XML data is available then you will have to take steps to prevent a crash, or at the very least a bad user experience. Typically you would display an activity spinner or a "loading data..." message until the data is ready, and in a background thread load the XML. Once loaded, the BG thread should signal to the UI thread that the data is ready, and perhaps invoke reloadData on the table to load the data.
This seems to be a common problem, but I can't figure out anything from the answers I've seen so far. I have an iPhone app that uses a subclass of NSMutableArray to store objects, plus some additional properties. The subclass is skhCustomArray. The subclass initializes fine, with no objects in the skhCustomArray, and I assign it to the the property of my view controller, which is a pointer to an skhCustomArray.
prescriptionListVC* newPrescList = [[prescriptionListVC alloc] initWithNibName:#"PrescriptionList" bundle:nil];
newPrescList.curPersonPrescriptions = [personDetails objectAtIndex:0];
That works fine. Yet when I push my view managed by my view controller onto the navigation controller stack, the count method in the numberOfRowsInSection method crashes the app, see below.
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
// Return the number of rows in the section.
return [curPersonPrescriptions count];
}
What could be causing this? How can a valid custom array, with no objects, not return a valid count? Where am I going wrong? Thanks.
Subclass of NSArray? You're aware that NSArray is a class cluster, and is therefore somewhat difficult to subclass, right? In fact, it's so fraught with danger that the NSArray documentation has a whole section dedicated to what you need to do in order to subclass it.
I'll bet that that's the source of your woes.
You almost certainly don't need to subclass NSMutableArray in this situation. Instead, make a new class which has an array as a property, along with the extra properties you desire.
When you subclass NSMutableArray, you need to implement some mandatory methods like count, addObject:, insertObjectAtIndex etc. This is what we call as class cluster.
If you want to add some more feature/behavior to already implemented object then you can write a "category" instead of "subclassing" it.
If you want to subclass it, then you have to implement all those methods which your are going to use so better write a category of NSMutableArray and extend the feature what you want and use the NSMutableArray object only. This will solve your problem and also this is the easy and almost right way to add new behavior to already existing class.