Question

Basicly, I’m making an app that lets you add or subtract by a certain number and I want to do so with a slider. How would I program a slider to be able to add or subtract by an integer by tapping a different button for adding and subtracting. For example, say you want to add by 3. You slide the bar to three then tap the “+” to add three. How would I program this?

EDIT: This is the code that I want to implement it in:

int number = 0

-(IBAction)IncrementNumber:(id)sender {
    number++;
    [currentNumber setText:[NSString stringWithFormat:@"%d", number]];
}

-(IBAction)DecrementNumber:(id)sender {
    number--;
    [currentNumber setText:[NSString stringWithFormat:@"%d", number]];
}

@synthesize MySlider, MyTextField;  

-(IBAction) sliderValueChanged:(UISlider *)sender {  
    MyTextField.text = [NSString stringWithFormat:@" %1.0f", [sender value]];  
}  

-(IBAction) changeButtonPressed:(id)sender {  
    NSString *textValue = [MyTextField text];  
    float value = [textValue floatValue];  
    if (value < 0) value = 1;  
    if (value > 100) value = 100;  
    MySlider.value = value;  
    MyTextField.text = [NSString stringWithFormat:@"%1.0f", value];  
    if ([MyTextField canResignFirstResponder]) [MyTextField resignFirstResponder];  
}  

-(void) touchesBegan: (NSSet *) touches withEvent: (UIEvent *) event {  
    if (MyTextField) {  
    if ([MyTextField canResignFirstResponder]) [MyTextField resignFirstResponder];  
}

Answer 1

You could bind the slider to some variable, and the two buttons, [+] and [-] to two functions, say add and sub.
When the functions are called, they grab the value from the variable, and add / subtract it to / from something.

In your edit, assuming that sliderValueChanged is called when the slider value is changed, that function should alter number, so that IncrementNumber and DecrementNumber can have the updated value.

What should work is to define number as IBOutlet in your header file (.h). Then, in interface builder, you can bind the value of the slider to number. This way, whenever you change de slider, the number variable changes accordingly.
In the interface, declare two functions that will be bound to the [+] and [-] boutons:

IBOutlet int number;
-(IBAction) add: (id) sender;
-(IBAction) sub: (id) sender;

In the definition of those functions, you take whatever number you want to change and add to it the number variable that you declared earlier.

Something like the following should do the trick, if value has the number you want to modify:

-(IBAction) add: (id) sender {
    value += number;
}
-(IBAction) sub: (id) sender {
    value -= number;
}

You could of course combine the two functions into one, and decide wether you should add or subtract according to which button was pressed (you get that by looking into the sender argument) but I think it’s less effective, and the code woud be more complex for no reason.