Question

I have a UIViewController (called AdjustViewController) that presents another UIViewController (called SourcePickerViewController) with a UIPickerView modally. I generate instances of the AdjustViewController and they in turn make a SourcePickerViewController. I make an NSDictionary and assign it and an integer to the AdjustViewController and it in turn sets the same properties in the SourcePickerController. This way I can reuse the controllers. The NSDictionary get set up in a UITableViewController that has all the AdjustViewControllers in it.

The problem comes when some of the pickers should have 1 component and some should have 2. The integer that I pass along is called numberOfComponents When I make a picker with numberOfComponents = 1 somehow it’s changing to = 2 but I can’t see how. I have NSLogs all over the place and I can see it happen as soon as the picker delegate method numberOfComponentsInPickerView is called. It’s 1 right before and 2 right after.

There’s obviously more code, but I think I have all the important parts. Although if that were true, maybe I’d know where the problem is!

---

Inside MenuViewController.m

- (void)viewDidLoad {
    NSLog(@"ChemicalViewController launched");
    self.title = @"Adjust Chemicals";
    NSMutableArray *array = [[NSMutableArray alloc] init];

// Chlorine Controller
    AdjustViewController *chlorineAdjustViewController = [[AdjustViewController alloc] initWithNibName:@"AdjustViewController" bundle:nil];
    chlorineAdjustViewController.title = @"FC - Free Chlorine";
    chlorineAdjustViewController.numberOfComponents = 2;
    NSLog(@"Generating chlorine source dictionary");
    NSDictionary *chlorineSourceDictionary = [self generateChlorineDictionary];
    chlorineAdjustViewController.dictionaryOfSources = chlorineSourceDictionary;
    [chlorineSourceDictionary release];
    [array addObject:chlorineAdjustViewController];
    [chlorineAdjustViewController release];

// CYA Controller
    AdjustViewController *cyaAdjustViewController = [[AdjustViewController alloc] initWithNibName:@"AdjustViewController" bundle:nil];
    cyaAdjustViewController.title = @"CYA - Cyanuric Acid";
    cyaAdjustViewController.numberOfComponents = 1;
    NSLog(@"Generating cya source dictionary");
    NSDictionary *cyaSourceDictionary = [self generateCYADictionary];
    cyaAdjustViewController.dictionaryOfSources = cyaSourceDictionary;
    [cyaSourceDictionary release];
    [array addObject:cyaAdjustViewController];
    [cyaAdjustViewController release];

---

Inside AdjustViewController.m

// Present the picker for chlorine selection
- (IBAction)getChemicalSource {
    SourcePickerViewController *sourcePickerViewController = [[SourcePickerViewController alloc] init];
    sourcePickerViewController.delegate = self;
    NSLog(@"getChemicalSource setting numberOfComponents %d", self.numberOfComponents);
    sourcePickerViewController.numberOfComponents = self.numberOfComponents;
    NSLog(@"getChemicalSource sending numberOfComponents %d", sourcePickerViewController.numberOfComponents);
    sourcePickerViewController.dictionaryOfSources = self.dictionaryOfSources;
    [self presentModalViewController:sourcePickerViewController animated:YES];
    [sourcePickerViewController release];
}

#pragma mark -
#pragma mark Picker View Delegate Methods

// Returns the values from the picker if a source was chosen
- (void)sourcePickerViewController:(SourcePickerViewController *)controller 
               didSelectSource:(NSString *)source 
              andConcentration:(NSString *)concentration 
                   andConstant:(float)constant 
                   andIsLiquid:(BOOL)isLiquid {


    sourceField.text = [[NSString alloc] initWithFormat:@"%@, %@", source, concentration];
    [self updateAdvice];
    NSLog(@"Returned source = %@, concentration = %@, sourceConstant = %1.7f, isLiquid = %d", source, concentration, constant, isLiquid);
    [self dismissModalViewControllerAnimated:YES];
}

// Returns from the picker without choosing a new source
- (void)sourcePickerViewController:(SourcePickerViewController *)controller 
               didSelectCancel:(BOOL)didCancel {
    [self updateAdvice];
    NSLog(@"Returned without selecting source");
    [self dismissModalViewControllerAnimated:YES];
}

---

Inside SourceViewController.m

- (void)viewDidLoad {
    NSLog(@"SourcePickerViewController launched");
    NSLog(@"viewDidLoad");
    NSLog(@"Received numberOfComponents %d", self.numberOfComponents);
    self.chemicalSources = dictionaryOfSources;
    NSArray *components = [self.chemicalSources allKeys];
    NSArray *sorted = [components sortedArrayUsingSelector:@selector(compare:)];
    self.sources = sorted; // This array has the chemical sources

    if (self.numberOfComponents = 2) {
        NSString *selectedSource = [self.sources objectAtIndex:0];
        NSArray *chemArray = [self.chemicalSources objectForKey:selectedSource];
        NSMutableArray *concentrationArray = [[NSMutableArray alloc] init];
        int num = [chemArray count];
        for (int i=0; i<num; i++) {
            [concentrationArray addObject:[[chemArray objectAtIndex:i] chemConcentration]];
        }
        self.concentrations = concentrationArray;
    }
    [super viewDidLoad];
}

    #pragma mark -
    #pragma mark Picker Data Source Methods

- (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView {
    NSLog(@"numberOfComponentsInPickerView, self.numberOfComponents = %d", self.numberOfComponents);
    return self.numberOfComponents;
}

- (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component {
    NSLog(@"numberOfRowsInComponent, self.numberOfComponents = %d", self.numberOfComponents);
    if (component == kSourceComponent)
        return [self.sources count];
    return [self.concentrations count];
}

#pragma mark Picker Delegate Methods

- (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component {
    if (component == kSourceComponent)
        return [self.sources objectAtIndex:row];
    return [self.concentrations objectAtIndex:row];
}

- (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component {
    NSLog(@"didSelectRow, self.numberOfComponents = %d", self.numberOfComponents);
    if (numberOfComponents = 2) {
        if (component == kSourceComponent) {
            NSString *selectedSource = [self.sources objectAtIndex:row];
            NSArray *chemArray = [self.chemicalSources objectForKey:selectedSource];
            NSMutableArray *concentrationArray = [[NSMutableArray alloc] init];
            int num = [chemArray count];
            for (int i=0; i<num; i++) {
                [concentrationArray addObject:[[chemArray objectAtIndex:i] chemConcentration]];
            }
    self.concentrations = concentrationArray;
    [picker selectRow:0 inComponent:kConcentrationComponent animated:YES];
    [picker reloadComponent:kConcentrationComponent];
    }
}
}

- (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component {
    if (component == kConcentrationComponent)
        return 90;
    return 205;
}

Answer 1

I didn’t look through all of your code; Instead, I’d recommend writing out the properties for numberOfComponents instead of @synthesize’ing them. Just get rid of your @synthesize, and make:

 - (int)numberOfComponents {
   return m_numberOfComponents;
}

and

 - (void)setNumberOfComponents(int aNumberOfComponents) {
   m_numberOfComponents = aNumberOfComponents;
}

Then, set a breakpoint in your setNumberOfComponents function, and you should be able to see whenever it’s getting called, so you can see what is going on. I hope that helps!