I have a view controller that is a subclass of UITableViewController. Here is my viewWillAppear:animated method:
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
if (fetchedResultsController != nil) {
[fetchedResultsController release];
fetchedResultsController = nil;
}
[self.fetchedResultsController performFetch:nil];
[self.tableView reloadData];
}
I am getting confused by seeing the fetchedResultsController being accessed when [super viewWillAppear:animated] is called. Since super is a UITableViewController, and there is no viewWillAppear:animated method for that class, per se, then its superclass viewWillAppear:animated should be called, right? If that's correct, then the UIViewController class should not be accessing UITableViewController delegate methods. But I see that numberOfSectionsInTableView is getting called. I'm not sure why the call to super viewWillAppear:animated would do this.
So before I explicitly run the peformFetch and reloadData, the table is getting populated. At that time, the data it is being populated with is out of date.
Here is the fetchedResultsController code
- (NSFetchedResultsController *) fetchedResultsController {
if (fetchedResultsController != nil) {
return fetchedResultsController;
}
NSFetchRequest *fetchRequest = ...
NSEntityDescription * entity = ...
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:10];
NSSortDescriptor *aSortDescriptor = ...
NSSortDescriptor *bSortDescriptor = ...
NSArray *sortDescriptors = ...
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController = ...
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[fetchRequest release];
...
[sortDescriptors release];
NSError *error = nil;
if (![fetchedResultsController performFetch:&error]) {
NSLog(#"Unresolved Error %#, %#", error, [error userInfo]);
abort();
}
return fetchedResultsController;
}
The documentation specifically describes this behaviour:
When the table view is about to appear the first time it’s loaded, the table-view controller reloads the table view’s data. It also clears its selection (with or without animation, depending on the request) every time the table view is displayed. The UITableViewController class implements this in the superclass method viewWillAppear:. You can disable this behavior by changing the value in the clearsSelectionOnViewWillAppear property.
Related
I am using Justin Driscoll's article on Core Data with UIManagedDocument in singleton pattern to set it up for UITabViewController. I am running the app on Simulator. Its working fine for the first time. The database is created successfully and I can see data in the tableview controller for each tab. But when I restart my application, the tableviews are empty because NSFetchRequest fetches 0 matches for the entity. The same fetch request fetches correct result during the first run.
I think its something to do with asynchronous nature of loading data and data not autosaving before I stop the app in simulator. So data is not available in second run of app.
The way I am doing my data loading as seen in the code. The fetchDataIntoDocument method does the initial loading of data.
// Document Handler Singleton Class
-(void) performWithDocument:(OnDocumentReady)onDocumentReady {
void (^OnDocumentDidLoad)(BOOL) = ^(BOOL Success) {
onDocumentReady(self.document);
};
if (![[NSFileManager defaultManager] fileExistsAtPath:[self.document.fileURL path]]) {
**[self fetchDataIntoDocument:self.document];**
[self.document saveToURL:self.document.fileURL forSaveOperation:UIDocumentSaveForCreating completionHandler:OnDocumentDidLoad];
} else if (self.document.documentState == UIDocumentStateClosed) {
[self.document openWithCompletionHandler:OnDocumentDidLoad];
} else if (self.document.documentState == UIDocumentStateNormal) {
OnDocumentDidLoad(YES);
}
}
-(void)fetchDataIntoDocument:(UIManagedDocument *)document {
MyEntityDataController *dc= [[MyEntityDataController alloc] init];
NSDictionary *entityInfo =[dc getEntityInfo];
[document.managedObjectContext performBlock:^{
[Entity createEntityWithInfo:entityInfo inManagedObjectContext:document.managedObjectContext];
}];
}
My TableViewController class
-(void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
if (!self.databaseDocument) {
[[LTDatabaseDocumentHandler sharedDatabaseDocumentHandler] performWithDocument:^ (UIManagedDocument *document) {
self.databaseDocument = document;
[self populateTableViewArrayFromDocument:self.databaseDocument];
}];
}
}
Within populateTableViewArrayFromDocument I am executing my fetch request
-(void)populateTableViewArrayFromDocument:(UIManagedDocument *)document
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:#"Entity2"];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
NSError *error = nil;
NSArray *matches = [self.databaseDocument.managedObjectContext executeFetchRequest:request error:&error];
NSLog(#" matches count for Entity2 %d", matches.count);
for (Entity2 *entity2 in matches) {
//do stuff with data and add it to tableview array
}
}
I think I have found why you have this problem. I have just run into this issue and it took some research to figure it out. Basically, you are right. The problem is indeed in the asynchronous nature of UIManagedDocument. You need to wait until the document loads into memory and then do your fetching.
This is the code I use to make sure the document is ready:
if ([[NSFileManager defaultManager] fileExistsAtPath:[_URLDocument path]]) {
[_managedDocument openWithCompletionHandler:^(BOOL success){
[self ready]
if (!success) {
// Handle the error.
}
}];
}
Hope this helps, cheers!
I have the following code to load a UIImagePickerController which works fine.
UIImagePickerController *mediaUI = [[UIImagePickerController alloc] init];
mediaUI.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
mediaUI.mediaTypes = [[NSArray alloc] initWithObjects: (NSString *) kUTTypeMovie, nil];
mediaUI.delegate = self;
[controller presentModalViewController: mediaUI animated: YES];
return YES;
I would like to load a modal view with some help information on how to use the UIImagePickerController:
UIStoryboard *storyboard = self.storyboard;
HelpViewController *svc = [storyboard instantiateViewControllerWithIdentifier:#"HelpViewController"];
[self presentViewController:svc animated:YES completion:nil];
How can I display the UIImagePickerController after the user dismisses the HelpViewController view?
Don't be tempted to move directly from HelpViewController to UIImagePickerController, you need to get there via your mainViewController.
Let's put your code into a method...
- (void) presentImagePicker {
UIImagePickerController *mediaUI = [[UIImagePickerController alloc] init];
mediaUI.sourceType = UIImagePickerControllerSourceTypeSavedPhotosAlbum;
mediaUI.mediaTypes = [[NSArray alloc] initWithObjects: (NSString *) kUTTypeMovie, nil];
mediaUI.delegate = self;
[controller presentModalViewController: mediaUI animated: YES];
return YES;
}
(Note that presentModalViewController:animated is depracated since ~iOS5, and you should really replace it with
[controller presentViewController:mediaUI animated:YES completion:nil];)
Let's call your viewControllers mainVC, helpVC and imageVC. There are two ways you can implement this.
method 1 - performSelector
The quick-and-slightly-dirty solution is to do this in your helpVC's dismiss button method:
- (IBAction)dismissHelpAndPresentImagePicker:(id)sender
{
UIViewController* mainVC = self.presentingViewController;
[mainVC dismissViewControllerAnimated:NO completion:
^{
if ([mainVC respondsToSelector:#selector(presentImagePicker)])
[mainVC performSelector:#selector(presentImagePicker)];
}];
}
It's slightly dirty because you need to ensure that presentImagePicker is implemented in mainVC - the compiler will give you no warnings if it is not. Also you are running a completion block after it's object has been dismissed, so there's no certainty it's going to work (in practice, it does, but still...)
Note that you have to assign the pointer self.presentingViewController's to a local variable (mainVC). That's because when helpVC is dismissed, it's presentingViewController property is reset to nil, so by the time you get to run the completion block you cannot use it. But the local variable mainVC is still valid.
method 2 - protocol/delegate
The clean way to do this is to use a protocol in helpVC to declare a delegate method, and make mainVC the delegate. This way the compiler will keep track of everything and warn you if it is not correctly implemented.
Here are the steps to do that:
In helpVC.h add this protocol above the #interface section:
#protocol helpVCDelegate
- (void) dismissHelpAndPresentImagePicker;
#end
In helpVC.h interface section declare a property for its delegate:
#property (nonatomic, weak) id <helpVCDelegate> delegate;
(the <helpVCDelegate> tells the compiler that the delegate is expected to conform to the protocol, so it will have to implement dismissHelpAndPresentImagePicker)
In helpVC.m your method can now look like this:
- (IBAction)dismissHelpAndPresentImagePicker:(id)sender
{
[self.delegate dismissHelpAndPresentImagePicker];
}
In MainVC, when you create HelpVC (=svc in your code), set MainVC as it's delegate:
HelpViewController *svc = [storyboard instantiateViewControllerWithIdentifier:#"HelpViewController"];
svc.delegate = self;
[self presentViewController:svc animated:YES completion:nil];
And be sure to implement the delegate method dismissHelpAndPresentImagePicker
- (void) dismissHelpAndPresentImagePicker
{
[self dismissViewControllerAnimated:NO completion:^{
[self presentImagePicker];
}];
}
Personally I would always use method 2. But I offered up a that solution earlier today to a similar question, and the questioner seemed to think protocol/delegate was overcomplicated. Maybe my answer just made it seem so, I have tried to simplify it here.
Here's a piece of code that I'm using to populate view-based NSTableView with data:
- (NSView *)tableView:(NSTableView *)tableView viewForTableColumn:(NSTableColumn *)tableColumn row:(NSInteger)row {
MyCustomCellView *view = (MyCustomCellView *)[tableView makeViewWithIdentifier:#"MyCustomCellView" owner:self];
if (!view) {
NSNib *cellNib = [[NSNib alloc] initWithNibNamed:#"MyCustomCellView" bundle:[NSBundle mainBundle]];
NSArray *array = nil;
if ([cellNib instantiateNibWithOwner:self topLevelObjects:&array]) {
DLog(#"%#", array);
view = [array objectAtIndex:0];
[view setIdentifier:#"MyCustomCellView"];
}
[cellNib release];
}
MyObject *object = [_objects objectAtIndex:row];
[[view titleTextField] setStringValue:object.title];
return view;
}
The DLog statement prints arrays as following for two consecutive delegate calls:
(
"<MyCustomCellView: 0x7fb2abe81f70>",
"<NSApplication: 0x7fb2ab80cbf0>"
)
(
"<NSApplication: 0x7fb2ab80cbf0>",
"<MyCustomCellView: 0x7fb2abb2c760>"
)
This is output only for two rows out of few hundred so I randomly either get my view displayed correctly or I get unrecognized selector error while calling setIdentifier: for view object when view being objectAtIndex:0 is actually an instance of NSApplication top level object from loaded nib.
Is this a bug in nib loading mechanism or am I doing something wrong with this code?
This thread is a little old, but for what it's worth:
It's not clear whether this is a bug, as the documentation is not specific as to the ordering of the array that's passed back in the topLevelObjects: parameter. However, this snippet has worked for me.
NSArray *arrayOfViews;
BOOL wasLoaded = [[NSBundle mainBundle] loadNibNamed:xibName owner:self topLevelObjects:&arrayOfViews];
NSUInteger viewIndex = [arrayOfViews indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
return [obj isKindOfClass:[MyCustomView class]];
}];
self = [arrayOfViews objectAtIndex:viewIndex];
Hi I set up my own coredata app, or I tried...
First I created the xdatamodel and generated the Modelclasses, after this I implemented all the function of core-data in AppDelegate which I found in a generated project. Finally I copied the fetchedResultsController in my TableViewController.
fetchedResultsController
- (NSFetchedResultsController *)fetchedResultsController {
if (fetchedResultsController_ != nil) {
return fetchedResultsController_;
}
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:#"ParameterGroup" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
[fetchRequest setFetchBatchSize:20];
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"name" ascending:NO];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"Root"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[fetchRequest release];
[sortDescriptor release];
[sortDescriptors release];
NSError *error = nil;
if (![fetchedResultsController_ performFetch:&error]) {
NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return fetchedResultsController_;
}
First I checked if the managedObjectsController is != nil, it has a address
Then I copied the EntityName from my xdatamodel in entityForName,
but NSEntityDescricption entity is nil.
And if I just create a new object the exception says, that the entity doesn't exist
Do I have to connect the xdatamodel to my project?
Hope you can help me
Thanks a lot!!!
The most common cause of this problem is simply misspelling the entity name wrong in the code such that it doesn't match the entity name in the data model.
Copy and paste the entity name from the model to the code and see if that fixes the problem.
The simplest way to solve this, given that you haven't done a lot coding on non-core-data parts, is probably to create a new project where you check the box for "Use Core Data". If you're going to use a Navigation Bar, choose this as your template. If I recall correctly, this will generate a table view with all functions needed. You'll have to modify the datamodel (generated).
Remark that you'll have to delete the app from the Simulator if it is installed and you change the datamodel (otherwise the generated data will not be consistent with the datamodel and the app will crash)
I'm relatively new to Core Data on iOS, but I think I've been getting better with it. I've been experiencing a bizarre crash, however, in one of my applications and have not been able to figure it out.
I have approximately 40 objects in Core Data, presented in a UITableView. When tapping on a cell, a UIActionSheet appears, presenting the user with a UIActionSheet with options related to the cell that was selected. So that I can reference the selected object, I declare an NSIndexPath in my header called "lastSelection" and do the following when the UIActionSheet is presented:
// Each cell has a tag based on its row number (i.e. first row has tag 0)
lastSelection = [NSIndexPath indexPathForRow:[sender tag] inSection:0];
NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:lastSelection];
BOOL onDuty = [[managedObject valueForKey:#"onDuty"] boolValue];
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:#"Status" delegate:self cancelButtonTitle:nil destructiveButtonTitle:nil otherButtonTitles:nil];
if(onDuty) {
[actionSheet addButtonWithTitle:#"Off Duty"];
} else {
[actionSheet addButtonWithTitle:#"On Duty"];
}
actionSheet.actionSheetStyle = UIActionSheetStyleBlackOpaque;
// Override the typical UIActionSheet behavior by presenting it overlapping the sender's frame. This makes it more clear which cell is selected.
CGRect senderFrame = [sender frame];
CGPoint point = CGPointMake(senderFrame.origin.x + (senderFrame.size.width / 2), senderFrame.origin.y + (senderFrame.size.height / 2));
CGRect popoverRect = CGRectMake(point.x, point.y, 1, 1);
[actionSheet showFromRect:popoverRect inView:[sender superview] animated:NO];
[actionSheet release];
When the UIActionSheet is dismissed with a button, the following code is called:
- (void)actionSheet:(UIActionSheet *)actionSheet willDismissWithButtonIndex:(NSInteger)buttonIndex {
// Set status based on UIActionSheet button pressed
if(buttonIndex == -1) {
return;
}
NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:lastSelection];
if([actionSheet.title isEqualToString:#"Status"]) {
if([[actionSheet buttonTitleAtIndex:buttonIndex] isEqualToString:#"On Duty"]) {
[managedObject setValue:[NSNumber numberWithBool:YES] forKey:#"onDuty"];
[managedObject setValue:#"onDuty" forKey:#"status"];
} else {
[managedObject setValue:[NSNumber numberWithBool:NO] forKey:#"onDuty"];
[managedObject setValue:#"offDuty" forKey:#"status"];
}
}
NSError *error;
[self.managedObjectContext save:&error];
[tableView reloadData];
}
This might not be the most efficient code (sorry, I'm new!), but it does work. That is, for the first 25 items in the list. Selecting the 26th item or beyond, the UIActionSheet will appear, but if it is dismissed with a button, I get a variety of errors, including any one of the following:
[__NSCFArray section]: unrecognized selector sent to instance 0x4c6bf90
Program received signal: “EXC_BAD_ACCESS”
[_NSObjectID_48_0 section]: unrecognized selector sent to instance 0x4c54710
[__NSArrayM section]: unrecognized selector sent to instance 0x4c619a0
[NSComparisonPredicate section]: unrecognized selector sent to instance 0x6088790
[NSKeyPathExpression section]: unrecognized selector sent to instance 0x4c18950
If I comment out NSManagedObject *managedObject = [self.fetchedResultsController objectAtIndexPath:lastSelection]; it doesn't crash anymore, so I believe it has something do do with that. Can anyone offer any insight? Please let me know if I need to include any other information. Thanks!
EDIT: Interestingly, my fetchedResultsController code returns a different object every time. Is this expected, or could this be a cause of my issue? The code looks like this:
- (NSFetchedResultsController *)fetchedResultsController {
/*
Set up the fetched results controller.
*/
// Create the fetch request for the entity.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
// Edit the entity name as appropriate.
NSEntityDescription *entity = [NSEntityDescription entityForName:#"Employee" inManagedObjectContext:self.managedObjectContext];
[fetchRequest setEntity:entity];
// Set the batch size to a suitable number.
[fetchRequest setFetchBatchSize:80];
// Edit the sort key as appropriate.
NSString *sortKey;
BOOL ascending;
if(sortControl.selectedSegmentIndex == 0) {
sortKey = #"startTime";
ascending = YES;
} else if(sortControl.selectedSegmentIndex == 1) {
sortKey = #"name";
ascending = YES;
} else {
sortKey = #"onDuty";
ascending = NO;
}
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:sortKey ascending:ascending];
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[fetchRequest setSortDescriptors:sortDescriptors];
// Edit the section name key path and cache name if appropriate.
NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:#"Root"];
aFetchedResultsController.delegate = self;
self.fetchedResultsController = aFetchedResultsController;
[aFetchedResultsController release];
[fetchRequest release];
[sortDescriptor release];
[sortDescriptors release];
NSError *error = nil;
if (![fetchedResultsController_ performFetch:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development. If it is not possible to recover from the error, display an alert panel that instructs the user to quit the application by pressing the Home button.
*/
//NSLog(#"Unresolved error %#, %#", error, [error userInfo]);
abort();
}
return fetchedResultsController_;
}
This happens when I set a breakpoint:
(gdb) po [self fetchedResultsController]
<NSFetchedResultsController: 0x61567c0>
(gdb) po [self fetchedResultsController]
<NSFetchedResultsController: 0x4c83630>
It's prob the case that self.fetchedResultsController is pointing to the wrong memory location. You will need to check if the object has been retained.
Figured it out! Looks like it was an issue with autoreleased objects.
When I turned on NSZombieEnabled, I got this:
*** -[NSIndexPath section]: message sent to deallocated instance 0xa674530
I simply changed lastSelection = [NSIndexPath indexPathForRow:[sender tag] inSection:0]; to lastSelection = [[NSIndexPath indexPathForRow:[sender tag] inSection:0] retain]; and that took care of it.