Question

I’m trying to get the basics of iOS programming down. I have an app that shows a random number when I click a button.. At least, that’s what I wanted to make. However, it doesn’t seem to be working out.

I have the following basic method which should set the text of myLabel to the return value of generateRandomNumber. However, it always returns 0. I think the syntax I’m using here is correct since it works for the commented parts:

-(IBAction)myBtnPressed:(UIButton *)sender
{
    //[myLabel setText:@"test"];
    //[myLabel setText:[NSString stringWithFormat:@"%g / 15", 3.14]];
    [myLabel setText:[NSString stringWithFormat:@"%g / 15", [myModel generateRandomNumber]]];
}

The last line sets the label to display 0/15. However, in my model, I have the following code (‘static’ for now):

-(double)generateRandomNumber
{
    randomNumber = 1.34;
    return randomNumber;
}

It doesn’t return the 1.34 and I don’t understand why it doesn’t. Can someone clear this up?

Update
This is the code for my viewcontroller.m file:

#import "myViewController.h"

@implementation myViewController

    -(MyModel *)myModel
    {
        if (! myModel) {
            myModel = [[MyModel alloc] init];
        }

        return myModel;
    }


    -(IBAction)myBtnPressed:(UIButton *)sender
    {
        [myLabel setText:[NSString stringWithFormat:@"%g / 15", [myModel generateRandomNumber]]];
    }

    @end

Also, in the end, I want to make generateRandomNumber return a random number between 0 and 15. How would I do this? Would a simple line like:

int x = arc4random() % 16;

work for this? Or do I have to seed it in some way so it doesn’t always return the same values when I run the application?

Thanks in advance.

Answer 1

It doesn’t return the 1.34 and I don’t understand why it doesn’t. Can someone clear this up?

Almost certainly, you haven’t allocated and initialised the myModel object. You can send messages to nil without crashing but the return value will be 0.

arc4random() doesn’t need a seed.

Edit

Your init code looks OK but you are not calling int, in your myBtnPressed: method, you need

[myLabel setText:[NSString stringWithFormat:@"%g / 15", [[self myModel] generateRandomNumber]]];