How to do an if statement with a button? - ios

Question

I'm new to Objective-C and am learning it bit by bit, and I have a question about it.
I made an iPhone app about incrementing or decreasing a number, for example, and the default number is set to 0. By pressing the Up, Down or Restart button you have different command options. I would like to put into play the if statement, for ex. when the Label number (0) equals five (5) have a popup box, or a text saying "You have reached the number 5"; this would only be to learn and be able to implement this in a future app or game.
ViewController.h
#import <UIKit/UIKit.h>
int Number;
#interface ViewController : UIViewController {
IBOutlet UILabel *Count;
}
- (IBAction)Up:(id)sender;
- (IBAction)Down:(id)sender;
- (IBAction)Restart:(id)sender;
#end
ViewController.m
#import "ViewController.h"
#interface ViewController ()
#end
#implementation ViewController
- (IBAction)Up:(id)sender {
Number = Number + 1;
Count.text = [NSString stringWithFormat:#"%i", Number];
}
- (IBAction)Down:(id)sender {
Number = Number - 1;
Count.text = [NSString stringWithFormat:#"%i", Number];
}
- (IBAction)Restart:(id)sender {
Number = 0;
Count.text = [NSString stringWithFormat:#"%i", Number];
}
- (void)viewDidLoad {
Number = 0;
Count.text = [NSString stringWithFormat:#"%i", Number];
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}

Answer 1

You can add a method:
- (void)checkNumber {
if (Number == 5) {
// show the alert
}
}
And then in your code:
-(IBAction)Up:(id)sender {
Number = Number + 1;
Count.text = [NSString stringWithFormat:#"%i", Number];
[self checkNumber];
}
-(IBAction)Down:(id)sender {
Number = Number - 1;
Count.text = [NSString stringWithFormat:#"%i", Number];
[self checkNumber];
}
Then, learn about naming conventions as your names are all wrong (letter capitalisation).

Answer 2

You will only hit 5 on the Up method, so check your value in there. Display a UIAlertView if someone tries to go over 5.
- (IBAction)Up:(id)sender{
if (Number >= 5) {
UIAlertView *alert = [[UIAlertView alloc ] initWithTitle:#"Sorry!" message:#"You can't go over five." delegate:nil cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alert show];
}
else {
Number = Number + 1;
Count.text = [NSString stringWithFormat:#"%i", Number];
}
}
I am using UIAlertView to show the message here, but you could use UILabel, or something else.
A few pointers about Objective-C conventions:
Methods use camel case, and have descriptive names. Instead of Up, use something like incrementTestValue.
Variable names also use camel case. Instead of Number and Count, just use number and countLabel, respectively. Using a capital makes it look like a class name.

Answer 3

Take a look at this code. This will be a good example of how to use return values inside your methods. My method is called -(BOOL)isNumberGreaterThanOrEqualToFive;
The - indicates this is an instance method. The (BOOL) indicates this method returns a BOOL (YES/NO). isNumberGreaterThanOrEqualToFive is the name of the method. It's used like this
BOOL value = [self isNumberGreaterThanOrEqualToFive];
//value will either be YES or NO
Take a look
-(BOOL)isNumberGreaterThanOrEqualToFive {
if (Number >= 5) {
return YES;
}
return NO;
}
-(IBAction)Up:(id)sender {
if ([self isNumberGreaterThanOrEqualToFive]) {
NSLog(#"Number is greater than or equal to 5");
[self showAlertViewWithMessage:#"Number is 5 or more!"];
} else {
Number = Number + 1;
}
}
Another thing to learn about Obj-C and programming in general is something called factorization, where you split up unrelated tasks into smaller more discrete related tasks. For example, instead of having one big block of code inside a method, you can make several methods that each complete one specific task. You could split out the code that shows the AlertView this way. For example:
-(void)showAlertViewWithMessage:(NSString *)messageText {
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:#"Alert" message:messageText delegate:nil cancelButtonTitle:#"Dismiss" otherButtonTitles:nil];
[alert show];
}