NSString's superclasses go on forever.

Question

I've got a method that when put a breakpoint in it and hover over a string, says it's out of scope and you can drill down into the NSString object for what seems like forever. I've tried to put a screen shot... hope it shows up. I think I have some serious memory management problems...

http://web.me.com/gazelips/Site/Blank_files/screenshot.jpg

Here's the whole .h and .m files. The problem occurs in the updateAdvice method.

#import <UIKit/UIKit.h>
#import "SourcePickerViewController.h"
#import "Chemical.h"

@interface AdjustViewController : UIViewController <SourcePickerViewControllerDelegate>{
// IB controls  
    UITextField *sourceField;
    UITextField *volumeField;
    UILabel *startingLabel;
    UILabel *targetLabel;
    UITextView *adviceLabel;
// Setup variables for the kind of chemical 
    int numberOfComponents;
    NSDictionary *dictionaryOfSources;
// Local ivars  
    float percentRemove;
    float gallonsRemove;
    float selectedChemSourceAmount;
    int delta;
    NSString *selectedChemName;
    NSString *selectedChemConcentration;
    float selectedChemConstant;
    BOOL selectedChemIsLiquid;
    NSString *compositeName;
    NSString *messageBody;
    NSString *adviceMessage;

}

@property (nonatomic, retain) IBOutlet UITextField *sourceField;
@property (nonatomic, retain) IBOutlet UITextField *volumeField;
@property (nonatomic, retain) IBOutlet UILabel *startingLabel;
@property (nonatomic, retain) IBOutlet UILabel *targetLabel;
@property (nonatomic, retain) IBOutlet UITextView *adviceLabel;

@property (nonatomic, retain) NSString *selectedChemName;
@property (nonatomic, retain) NSString *selectedChemConcentration;
@property float selectedChemConstant;
@property BOOL selectedChemIsLiquid;
@property (nonatomic, retain) NSString *compositeName;
@property (nonatomic, retain) NSString *messageBody;
@property (nonatomic, retain) NSString *adviceMessage;

@property int numberOfComponents;
@property (nonatomic, retain) NSDictionary *dictionaryOfSources;

- (IBAction)backgroundTap:(id)sender;
//- (IBAction)textFieldDoneEditing:(id)sender;
- (IBAction)startingSliderChanged:(id)sender;
- (IBAction)startingSliderFinishedChanging;
- (IBAction)targetSliderChanged:(id)sender;
- (IBAction)targetSliderFinishedChanging;
- (IBAction)getChemicalSource;
- (void)updateAdvice;

@end

---

#import "AdjustViewController.h"

@implementation AdjustViewController

@synthesize sourceField;
@synthesize volumeField;
@synthesize startingLabel;
@synthesize targetLabel;
@synthesize adviceLabel;
@synthesize numberOfComponents;
@synthesize dictionaryOfSources;
@synthesize compositeName;
@synthesize messageBody;
@synthesize adviceMessage;
@synthesize selectedChemName;
@synthesize selectedChemConcentration;
@synthesize selectedChemConstant;
@synthesize selectedChemIsLiquid;

- (IBAction)backgroundTap:(id)sender {
    [sourceField resignFirstResponder];
    [volumeField resignFirstResponder];
    [self updateAdvice];
}

- (IBAction)startingSliderChanged:(id)sender {
    UISlider *slider = (UISlider *)sender;
    int progressAsInt = (int)(slider.value + 0.5f);
    NSString *newValue = [[NSString alloc] initWithFormat:@"%d", progressAsInt];
    startingLabel.text = newValue;
    [newValue release];
}

- (IBAction)targetSliderChanged:(id)sender {
    UISlider *slider = (UISlider *)sender;
    int progressAsInt = (int)(slider.value + 0.5f);
    NSString *newValue = [[NSString alloc] initWithFormat:@"%d", progressAsInt];
    targetLabel.text = newValue;
    [newValue release];
}

- (IBAction)startingSliderFinishedChanging {
//  [self updateAdvice];
}

- (IBAction)targetSliderFinishedChanging {
//  [self updateAdvice];
}


// 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];
}

- (void)updateAdvice {
     NSLog(@"--updateAdvice");
     NSLog(@"  selectedChemical name = %@", selectedChemName);
     NSLog(@"  selectedChemical concentration = %@", selectedChemConcentration);
     NSLog(@"  selectedChemical constant = %1.6f", selectedChemConstant);
     NSLog(@"  selectedChemical is liquid = %d", selectedChemIsLiquid);
// First check to see if there is a source AND volume, otherwise prompt user to enter them
if ([volumeField.text isEqualToString:@""] || [sourceField.text isEqualToString:@""]) {
    adviceMessage = @"Enter a source and volume.";
 }
// If there IS a source and volume, calculate!
 else {
  if ([selectedChemConcentration isEqualToString:@""]) { // If there's no concentration, make a string with just the name
   compositeName = selectedChemName;
   NSLog(@"  compositeName without concentration = %@", compositeName);
  }
  else { // But if there is a concentration, make a string with the name and concentration and a space between.
   compositeName = [[NSString alloc] initWithFormat:@"%@ %@", selectedChemName, selectedChemConcentration];
   NSLog(@"  compositeName with concentration = %@ %@", compositeName, selectedChemConcentration);
  }
  delta = [targetLabel.text intValue] - [startingLabel.text intValue]; // The difference between target and starting levels
  NSLog(@"  delta = %d", delta);
  sourceAmount = delta * [volumeField.text intValue] * sourceConstant; // Calculates the amount of source chemical necessary in ounces
  NSLog(@"  sourceAmount = %1.1f", sourceAmount);

// If delta is positive, add chemical
  if (delta > 0) {
   NSLog(@">> Delta > 0");
   if (selectedChemIsLiquid) {
    if (sourceAmount > 128) { // Amount is more than a gallon
     sourceAmount = sourceAmount / 128;
     messageBody = [[NSString alloc] initWithFormat:@"To increase %@ by %d ppm, add %1.1f gal of ", self.title, delta, sourceAmount]; 
    }
    else { // Less than a gallon
     messageBody = [[NSString alloc] initWithFormat:@"To increase %@ by %d ppm, add %1.1f fl oz of ", self.title, delta, sourceAmount];
    }
   }
   else { // Chemical is a solid
    if (sourceAmount > 16) { // Amount is more than a pound
     sourceAmount = sourceAmount / 16;
     messageBody = [[NSString alloc] initWithFormat:@"To increase %@ by %d ppm, add %1.1f lb of ", self.title, delta, sourceAmount]; 
    }
    else { // Less than a pound
     messageBody = [[NSString alloc] initWithFormat:@"To increase %@ by %d ppm, add %1.1f oz of ", self.title, delta, sourceAmount];
    }
   }
   adviceMessage = [[NSString alloc] initWithFormat:@"%@%@.", messageBody, compositeName];
  }
// If delta is zero, stay the course
  if (delta == 0) {
   NSLog(@"== Delta = 0");
   adviceMessage = @"You're on target.  No action necessary.";
  }
// If delta is negative, remove water 
  if (delta < 0) {
            NSLog(@"<< Delta < 0");
   adviceMessage = @"You're over target.  Remove some water.";
  }

 }
 adviceLabel.text = adviceMessage; // Set the advice label
 [messageBody release]; // And get rid of message
 [compositeName release];
 [adviceMessage release];
}

- (void)viewDidLoad {
    NSLog(@"AdjustViewController launched");
    sourceField.text = @"";
    adviceLabel.text = @"";
    percentRemove = 0;
    gallonsRemove = 0;
    delta = 0;
    selectedChemSourceAmount = 0;
//  [self updateAdvice];
    [super viewDidLoad];
}

- (void)didReceiveMemoryWarning {
    // Releases the view if it doesn't have a superview.
    [super didReceiveMemoryWarning];

    // Release any cached data, images, etc that aren't in use.
}

- (void)viewDidUnload {
    sourceField = nil;
    volumeField = nil;
    startingLabel = nil;
    targetLabel = nil;
    adviceLabel = nil;
    dictionaryOfSources = nil;
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (void)dealloc {
    [sourceField release];
    [volumeField release];
    [startingLabel release];
    [targetLabel release];
    [adviceLabel release];
    [dictionaryOfSources release];
    [super dealloc];
}

#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 {

    selectedChemName = source;
    selectedChemConcentration = concentration;
    selectedChemConstant = constant;
    selectedChemIsLiquid = isLiquid;

//    Update the source textfield.  If concentration is empty, just use the source otherwise concatenate them       
    if ([selectedChemConcentration isEqualToString:@""]) {
        sourceField.text = [[NSString alloc] initWithFormat:@"%@", selectedChemName];
    }
    else    {
        sourceField.text = [[NSString alloc] initWithFormat:@"%@ %@", selectedChemName, selectedChemConcentration];
    }
//    [self updateAdvice];
    NSLog(@"Returned source = %@, concentration = %@, constant = %1.7f, isLiquid = %d", source, concentration, constant, isLiquid);
    NSLog(@"selectedChemical.chemName = %@, chemConcentration = %@, chemConstant = %1.7f, chemIsLiquid = %d", selectedChemName, selectedChemConcentration, selectedChemConstant, selectedChemIsLiquid);
    [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];
}

@end

Answer 1

This is actually quite common and not necessarily anything to do with a bug in your code.

If you right click on the string object in the debugger window and select "print description to console", it should work just fine.

Answer 2

I'm just looking at your code anyway. What the other two people said hold... however, memory management issues:

    if (sourceAmount > 16) { // Amount is more than a pound
     sourceAmount = sourceAmount / 16;
     messageBody = [[NSString alloc] initWithFormat:@"To increase %@ by %d ppm, add %1.1f lb of ", self.title, delta, sourceAmount]; 
    }
    else { // Less than a pound
     messageBody = [[NSString alloc] initWithFormat:@"To increase %@ by %d ppm, add %1.1f oz of ", self.title, delta, sourceAmount];
    }
[...]
 [messageBody release]; // And get rid of message
 [compositeName release];
 [adviceMessage release];

I think it would be better for you to simply write

self.messageBody = [NSString stringWithFormat:@"To increase %@...", self.title];

This automatically invokes the accessor methods which you synthesized using @synthesize messageBody. It will automatically release the old string, and retain the new one. What you are doing right now is allocating a new string without releasing the old string. And why do that yourself when you have already synthesized the accessor methods?

Finally, don't forget to properly release the messageBody in dealloc, where you should be releasing it.

- (void)dealloc
{
    [messageBody release];
    [everythingElseIHaveToRelease release];

    [super dealloc];
}

Hope that helps! H