I am getting mixed results from random number code - objective-c

Question

for a class project we've been asked to create an app. In part my app includes a coin counting app where a random amount is generated and the user is required to click on the coin buttons until the correct amount is reached.
here is the .m code...
//
// CountingChangeViewController.m
// Piggy Bank
//
#import "CountingChangeViewController.h"
#interface CountingChangeViewController ()
//define button connections
- (IBAction)PennyButton:(id)sender;
- (IBAction)NickelButton:(id)sender;
- (IBAction)DimeButton:(id)sender;
- (IBAction)QuarterButton:(id)sender;
- (IBAction)ResetButton:(id)sender;
//define UILable connections
#property (weak, nonatomic) IBOutlet UILabel *labelAmountRequired;
#property (weak, nonatomic) IBOutlet UILabel *labelAmountInBank;
#property (weak, nonatomic) IBOutlet UILabel *labelAmountRemaining;
#property (weak, nonatomic) IBOutlet UILabel *labelCoinCount;
#property (weak, nonatomic) IBOutlet UIImageView *imagePickNewCoin;
#property (weak, nonatomic) IBOutlet UILabel *labelPennyCount;
#property (weak, nonatomic) IBOutlet UILabel *labelNickelCount;
#property (weak, nonatomic) IBOutlet UILabel *labelDimeCount;
#property (weak, nonatomic) IBOutlet UILabel *labelQuarterCount;
#end
//declare class variables
double AmountTotal = 0;
double AmountBank = 0;
double AmountRemaining = 0;
double rNumberMod;
double coinValue;
int coinCount = 0;
int pennyCount = 0;
int nickelCount = 0;
int dimeCount = 0;
int quarterCount = 0;
//start implementation
#implementation CountingChangeViewController
- (void)resetPage{
_imagePickNewCoin.hidden=YES;
//simply generates a new random amount
AmountTotal = [self RandomNumber];
_labelAmountRequired.text = [NSString stringWithFormat:#"$%.2f", AmountTotal];
AmountBank = 0;
_labelAmountInBank.text = [NSString stringWithFormat:#"$%.2f", AmountBank];
AmountRemaining = 0;
_labelAmountRemaining.text = [NSString stringWithFormat:#"$%.2f", AmountRemaining];
coinCount = 0;
_labelCoinCount.text = [NSString stringWithFormat:#"%d", coinCount];
pennyCount = 0;
_labelPennyCount.text = [NSString stringWithFormat:#"%d", pennyCount];
nickelCount = 0;
_labelNickelCount.text = [NSString stringWithFormat:#"%d", nickelCount];
dimeCount = 0;
_labelDimeCount.text = [NSString stringWithFormat:#"%d", dimeCount];
quarterCount = 0;
_labelQuarterCount.text = [NSString stringWithFormat:#"%d", quarterCount];
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
[self resetPage];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)PennyButton:(id)sender {
pennyCount++;
_labelPennyCount.text =[NSString stringWithFormat:#"%d",pennyCount];
coinValue = .01;
[self checkValue];
}
- (IBAction)NickelButton:(id)sender {
if ((AmountRemaining > 0) && (AmountRemaining <= .04))
{
//display the error message
_imagePickNewCoin.hidden=NO;
}
else
{
nickelCount++;
_labelNickelCount.text =[NSString stringWithFormat:#"%d",nickelCount];
coinValue = .05;
[self checkValue];
}
}
- (IBAction)DimeButton:(id)sender {
if ((AmountRemaining > 0) && (AmountRemaining <= .09))
{
//display the error message
_imagePickNewCoin.hidden=NO;
}
else
{
dimeCount++;
_labelDimeCount.text =[NSString stringWithFormat:#"%d",dimeCount];
coinValue = .10;
[self checkValue];
}
}
- (IBAction)QuarterButton:(id)sender {
if ((AmountRemaining > 0) && (AmountRemaining <= .24))
{
//display the error message
_imagePickNewCoin.hidden=NO;
}
else
{
quarterCount++;
_labelQuarterCount.text =[NSString stringWithFormat:#"%d",quarterCount];
coinValue = .25;
[self checkValue];
}
}
-(double)RandomNumber{
int rNumber = arc4random_uniform(99) +1;
double rNumberMod = rNumber * .01;
return rNumberMod;
}
-(void)checkValue {
//hide the error message
_imagePickNewCoin.hidden=YES;
//at button press play coin drop sound
SystemSoundID soundID;
NSString *soundFile = [[NSBundle mainBundle]
pathForResource :#"coin-drop-1" ofType :#"mp3"];
AudioServicesCreateSystemSoundID ((__bridge CFURLRef)
[NSURL fileURLWithPath :soundFile]
, &soundID);
AudioServicesPlaySystemSound (soundID);
//add coinvalue to amountTotal and put the resulting value in the AmountInBank UILabel .text attribute
//this is the math occuring behind the scenes
AmountBank = AmountBank + coinValue;
//this is how the math result shows on the screen
_labelAmountInBank.text = [NSString stringWithFormat:#"$%.2f", AmountBank];
//calculate the amountRemaining and put the resulting value in the AmountRemaining UILabel .text attribute
//this is the math occuring behind the scenes
AmountRemaining = AmountTotal - AmountBank;
//this is how the math result shows on the screen
_labelAmountRemaining.text = [NSString stringWithFormat:#"$%.2f", AmountRemaining];
// increment coin count by one and display it on the screen
coinCount++;
_labelCoinCount.text =[NSString stringWithFormat:#"%d",coinCount];
//test to see if the AmountRemaining = 0
if (AmountRemaining == 0)
{
UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:#"CONGRATULATIONS!" message:#"You saved the correct amount of money! Would you like to try again?" delegate:self cancelButtonTitle:nil otherButtonTitles:#"TRY AGAIN", nil];
[alertView show];
}
}
- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {
if (buttonIndex == 0)
[self resetPage];
}
- (IBAction)ResetButton:(id)sender {
[self resetPage];
}
#end
Sometimes it works and sometimes it doesn't. It is supposed to bring up an alert view when the amount of change needed reaches 0. Sometimes it does and other times it doesn't. Also when amountRemaining is less than the value of the coin button clicked it is supposed to show a hidden image "imagePickNewCoin" instead of adding the coin's value to the bank amount. Sometimes this works and other times it performes the calculation anyway resulting in a negative value for amountRemaining.
Why would this work sometimes and not other times?