populate uipicker view with results from core data DB using an NSArray
- by Chris
I am trying to populate a UIPickerView with the results of a NSFetchRequest. The results of the NSFetchRequest are then stored in an NSArray. I am using Core Data to interact with the SQLite DB. I have a simple class file that contains a UIPickerView that is associated with a storyboard scene in my project.
The header file for the class looks like the following,
ViewControllerUsers.h
#import <UIKit/UIKit.h>
#import "AppDelegate.h"
@interface ViewControllerUsers : UIViewController <NSFetchedResultsControllerDelegate, UIPickerViewDelegate, UIPickerViewDataSource>
{
NSArray *dictionaries;
}
@property (nonatomic, strong) NSFetchedResultsController *fetchedResultsController;
// Core Data
@property (strong, nonatomic) NSManagedObjectContext *managedObjectContext;
@property (nonatomic, strong) NSArray *users;
@property (strong, nonatomic) IBOutlet UIPickerView *uiPickerViewUsers;
@property (weak, nonatomic) IBOutlet UIBarButtonItem *btnDone;
@property (weak, nonatomic) IBOutlet UIButton *btnChangePin;
// added for testing purposes
@property (nonatomic, strong) NSArray *usernames;
- (IBAction)dismissScene:(id)sender;
- (IBAction)changePin:(id)sender;
@end
The implementation file looks like the following,
ViewControllerUsers.m
#import "ViewControllerUsers.h"
@interface ViewControllerUsers ()
@end
@implementation ViewControllerUsers
// Core Data
@synthesize managedObjectContext = _managedObjectContext;
@synthesize uiPickerViewUsers = _uiPickerViewUsers;
@synthesize usernames = _usernames;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
// Core Data
if (_managedObjectContext == nil)
{
_managedObjectContext = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
NSLog(@"After _managedObjectContext: %@", _managedObjectContext);
}
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Account"];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Account" inManagedObjectContext:_managedObjectContext];
request.resultType = NSDictionaryResultType;
request.propertiesToFetch = [NSArray arrayWithObject:[[entity propertiesByName] objectForKey:@"username"]];
request.returnsDistinctResults = YES;
_usernames = [_managedObjectContext executeFetchRequest:request error:nil];
NSLog (@"names: %@",_usernames);
}
-(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
//One column
return 1;
}
-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
//set number of rows
return _usernames.count;
}
-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
//set item per row
return [_usernames objectAtIndex:row];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)viewDidUnload {
[self setBtnDone:nil];
[self setUiPickerViewUsers:nil];
[self setBtnChangePin:nil];
[super viewDidUnload];
}
- (IBAction)dismissScene:(id)sender {
[self dismissModalViewControllerAnimated:YES];
}
- (IBAction)changePin:(id)sender {
}
@end
The current code is causing the app to crash, but the NSLog is show the results of the NSFetchRequest in the NSArray. I currently think that I am not formatting the results of the NSFetchRequest in the NSArray properly if I had to take a guess.
The crash log looks like the following,
2013-06-26 16:49:24.219 KegCop[41233:c07] names: (
{
username = blah;
},
{
username = chris;
},
{
username = root;
}
)
2013-06-26 16:49:24.223 KegCop[41233:c07] -[NSKnownKeysDictionary1 isEqualToString:]: unrecognized selector sent to instance 0xe54d9a0
2013-06-26 16:49:24.223 KegCop[41233:c07] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSKnownKeysDictionary1 isEqualToString:]: unrecognized selector sent to instance 0xe54d9a0'
First throw call stack:
