UIPickerView not loading rows

Question

Currently working on an app for spotting trains using CoreData. Basically, each train is stored with a corresponding set of sightings. When a user sees a train they log a sighting and that sighting is tied back to a train serial number (just basic data relationships)

I'm trying to populate a UIPickerView with serial numbers however I am running into some difficulty. I'm planning on using this specific PickerView multiple times, so it has its own class and is not implemented in the ViewController.

I have set the delegate and dataSource correctly, but the PickerView is never populated. From the NSLog and printf code that is in each function I can tell that titleForRow is never called, and neither is numberOfRowsInComponent Here is my code for the UIPickerView class:

-(id)init
{
    //init super class.
    self = [super init];

    //get allocate array reader (TrainSightingReaderWriter) then set the array that this picker will be getting data from.
    [self setArrayReader:[[TrainSightingReaderWriter alloc] init]];
    [self setArray: [[self arrayReader] getTrainSerialArray]];

    NSLog(@"INIT PickerView");

    //return this object.
    return self;
}

-(int)numberOfComponentsInPickerView:(UIPickerView *)pickerView
{
    printf("At component counter\n");
    return 1;
}

-(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component
{
    printf("At counter. %d is output\n", _array.count);
    return _array.count;
}

-(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component
{
    NSLog(@"Returning a value.");
    return [self array][row];
}

ViewController code:

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSLog(@"We have made it to the AddSightVC.");
    TrainPicker * mypicker;
    mypicker = [[TrainPicker alloc]init];


    //ISSUES
    _trainPickerScroller.delegate = mypicker;
    _trainPickerScroller.dataSource = mypicker;

    [_trainPickerScroller reloadAllComponents];
    [_trainPickerScroller reloadInputViews];

    // Do any additional setup after loading the view.
}

Answer 1

TrainPicker needs to be an instance variable for the view controller so that it is not garbage collected (either in the .h as a property or in an interface section in the .m file). Creating a local variable in viewDidLoad for it will cause it to be garbage collected if you are using ARC.