get all attributes for entity from core data - core-data

Question

how does my fetchedResultsController method look like, if I want to fetch all my attributes for an entity from core data? I only know and understand how to fetch data for a tableView and I think that is where all my confusion is coming from.
Here is my Core-Data setup:
I'm trying to fill an array with all the Attributes my Setting entity has and the show those values via NSLog output in my debug console.
Here is what I changed so far:
AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
NSManagedObject *newEntry = [NSEntityDescription insertNewObjectForEntityForName:#"Setting" inManagedObjectContext:context];
//NSManagedObject *newSetting = [NSEntityDescription insertNewObjectForEntityForName:#"Setting" inManagedObjectContext:context];
[newEntry setValue: #"StudiSoft" forKey:#"settingName"];
if (_overrideSysTimeSwitch.on) {
[newEntry setValue: #YES forKey:#"settingSysTimeOverride"];
//editSetting.settingSysTimeOverride = #YES;
NSLog(#"IF A");
} else {
//[newEntry setValue: #NO forKey:#"settingSysTimeOverride"];
//editSetting.settingSysTimeOverride = #NO;
NSLog(#"IF B");
}
if (_timeFormatSwitch.on) {
//[newEntry setValue: #YES forKey:#"settingTimeFormat"];
//editSetting.settingTimeFormat = #YES;
NSLog(#"IF C");
} else {
//[newEntry setValue: #NO forKey:#"settingTimeFormat"];
//editSetting.settingTimeFormat = #NO;
NSLog(#"IF D");
}
[self.settingsArray addObject:#"StudiSoft"];
NSError *error;
[context save:&error];
I'm using this code-snipped that and I'm able to modify the core data content.
However, every time I run this code, it of course adds a new object.
I've been looking for a way to update existing Attributes in my Entity, or modify them, but I could NOT find them.
Anyhow this is a good step into the right direction.
I created a completely new project, with just one view, once I have it working on the main view I'm going to experiment with segues....
But for now, how would I update or change existing attributes?
Thanks guys!!
This is my editSave Method to store some data in core data:
- (IBAction)editSave:(UIBarButtonItem *)sender
{
if ([_editSaveButton.title isEqualToString:#"Edit"])
{
[self setTitle:#"Edit Settings"];
//self.title = #"Edit Settings";
_overrideSysTimeSwitch.userInteractionEnabled = YES;
_timeFormatSwitch.userInteractionEnabled = YES;
_editSaveButton.title = #"Save";
} else if ([_editSaveButton.title isEqualToString:#"Save"])
{
[self setTitle:#"Settings"];
//self.title = #"Settings";
_overrideSysTimeSwitch.userInteractionEnabled = NO;
_timeFormatSwitch.userInteractionEnabled = NO;
_editSaveButton.title = #"Edit";
// #############################################################
AppDelegate *appDelegate = [[UIApplication sharedApplication] delegate];
NSManagedObjectContext *context = [appDelegate managedObjectContext];
//NSManagedObject *newEntry = [NSEntityDescription insertNewObjectForEntityForName:#"Setting" inManagedObjectContext:context];
//[newEntry setValue: #"StudiSoft" forKey:#"settingName"];
/*NSString *firstName = [anEmployee firstName];
Employee *manager = anEmployee.manager;
Setting *newSetting = [NSString #"Test"];
[newSetting setValue:#"Stig" forKey:#"settingName"];
[aDepartment setValue:[NSNumber numberWithInteger:100000] forKeyPath:#"manager.salary"];*/
//editSetting.settingName = #"Test";
if (_overrideSysTimeSwitch.on) {
//[newEntry setValue: #YES forKey:#"settingSysTimeOverride"];
editSetting.settingSysTimeOverride = #YES;
NSLog(#"IF A");
} else {
//[newEntry setValue: #NO forKey:#"settingSysTimeOverride"];
editSetting.settingSysTimeOverride = #NO;
NSLog(#"IF B");
}
if (_timeFormatSwitch.on) {
//[newEntry setValue: #YES forKey:#"settingTimeFormat"];
editSetting.settingTimeFormat = #YES;
NSLog(#"IF C");
} else {
//[newEntry setValue: #NO forKey:#"settingTimeFormat"];
editSetting.settingTimeFormat = #NO;
NSLog(#"IF D");
}
//[self.settingsArray addObject:#"StudiSoft"];
NSError *error = nil;
//if ([self.managedObjectContext hasChanges]) {
//NSLog(#"SAVE & DISMISS conetx has changed");
if (![context save:&error]) { // save failed
NSLog(#"Save failed: %#", [error localizedDescription]);
} else { // save succeeded
NSLog(#"Save Succeeded");
}
//}
//[self.tableView reloadData];
// #############################################################
}
}
Debug Output:
2014-06-10 19:09:29.881 SettingsCoreData[508:60b] Entry #5: <Setting: 0x8f983e0> (entity: Setting; id: 0x8f97030 <x-coredata://FA78AB86-3225-4B1E-97DD-3F31F5323A18/Setting/p6> ; data: {
settingName = StudiSoft;
settingSysTimeOverride = 0;
settingTimeFormat = 0;
})
2014-06-10 19:09:29.883 SettingsCoreData[508:60b] Entry #6: <Setting: 0x8f98430> (entity: Setting; id: 0x8f97040 <x-coredata://FA78AB86-3225-4B1E-97DD-3F31F5323A18/Setting/p7> ; data: {
settingName = StudiSoft;
settingSysTimeOverride = 1;
settingTimeFormat = 1;
})
Now I should be able to use something like this in my viewDidLoad, right?
if (editSetting.settingSysTimeOverride.boolValue == 0) {
_overrideSysTimeSwitch.on = NO;
} else {
_overrideSysTimeSwitch.on = YES;
}
But it doesn't work as I thought it will :-(

Answer 1

Next you need to call -performFetch: on the NSFetchedResultsController. Make sure you check the response and handle the error if the response is NO.
From there your NSFetchedResultsController is populated and ready to be used. You can then grab individual elements via -objectAtIndex: or you can grab them all with -fetchedObjects.
I would suggest just reviewing the documentation on the methods that are available as it has pretty strong and clear documentation.
Update
If you are not receiving any data then break it down. Take the NSFetchRequest that you created and call -executeFetchRequest:error: against your NSManagedObjectContext and see if you get any data back.
If you do then there is something wrong with your handling of the NSFetchedResultsController.
If you don't then there is something wrong with your NSFetchRequest or you don't have any data in your store.
Update
Sounds like you need to read a book on how Core Data works.
A NSFetchRequest is a query against Core Data so that objects can be returned from the store. You can pass a NSFetchRequest to a NSFetchedResultsController so that the NSFetchedResultsController can monitor the store for changes and let your view controller know when those changes occur.
A NSFetchRequest can also be executed directly against the NSManagedObjectContext and you can retrieve the results directly. You do that by calling -executeFetchRequest:error: against your NSManagedObjectContext and getting a NSArray back. You can then check that NSArray to see if you get any results.
If you do not understand that paragraph then you need to take a step back and read the tutorials on Core Data and/or read a book on Core Data. I can recommend an excellent book on the subject ;-)