How to change number of decimal places and add decimal button iPhone Calculator?

So, look at the following code below- my first question is, how can I make it so there is only 0, 1, or 2 decimal places or make it automatically have however many decimal places are there? the second question is, how would I add a decimal button to the calculator? it has +-/*, how would I add a decimal button? Tutorial I used is here http://www.youtube.com/watch?v=Ihw0cfNOrr4 and here is my code-

viewcontroller.h

 #import <UIKit/UIKit.h>

@interface calcViewController : UIViewController {

float result;
IBOutlet UILabel *calculatorScreen;
int currentOperation;
float currentNumber;

}


-(IBAction)buttonDigitPressed:(id)sender;
-(IBAction)buttonOperationPressed:(id)sender;
-(IBAction)cancelInput;
-(IBAction)cancelOperation;



@end

in the .m

 #import "calcViewController.h"

@implementation calcViewController



-(IBAction)buttonDigitPressed:(id)sender {


currentNumber = currentNumber *10 + (float)[sender tag];
calculatorScreen.text = [NSString stringWithFormat:@"%2f", currentNumber];

}

-(IBAction)buttonOperationPressed:(id)sender {
if (currentOperation ==0) result = currentNumber;
else {


    switch (currentOperation) {
        case 1:
            result = result + currentNumber;
            break;
        case 2:
            result = result - currentNumber;
            break;
        case 3:
            result = result * currentNumber;
            break;
        case 4:
            result = result / currentNumber;
            break;
        case 5:
         开发者_Go百科  currentOperation = 0;
            break;




    }
}
currentNumber = 0;
calculatorScreen.text = [NSString stringWithFormat:@"%2f", result];
if ([sender tag] ==0) result=0;
currentOperation = [sender tag];

}

-(IBAction)cancelInput {

currentNumber =0;
calculatorScreen.text = @"0";

}


-(IBAction)cancelOperation {



currentNumber = 0;
calculatorScreen.text = @"0";
currentOperation = 0;

}

---

you can use this on the output.

Float *number = 2.2f;
NSLog(@"%.2f",number);

---

Another thing you want to take note about the point is that you do not want to have multiple point in your calculation, e.g. 10.345.1123.5. Simply put, you want it to be a legal float number as well.

With that said, you can use a IBAction (remember to link it to your storyboard or xib file)

-(IBAction)decimalPressed:(UIButton *)sender
{
 NSRange range = [self.display.text rangeOfString:@"."];
if (range.location ==NSNotFound){
self.display.text = [ self.display.text stringByAppendingString:@"."];
}
self.userIsInTheMiddleOfEnteringANumber = YES;
}

While it might be possible we are doing on the same project, it could also be entirely different (you starting from scratch by yourself) so i will go through some of the codes

you could replace UIButton with the default id, but it is better to static replace it to make clear clarification for yourself, or anyone else who view your code.

NSRange as the name implies, mark the range, and the range will be ur display text of calculation (e.g. 1235.3568), and the range of string it is targeting in this case is "." therefore, if NSNotfound (rangeOfString "." is not found in the text range) you will append the current display text with "." with the function stringByAppendingString:@".", there is no else, so no function will take place if "." is already found, which solve the problem of multiple point on the display.

userIsInTheMiddleOfEnteringANumber is a BOOL to solve the problem of having 0 in ur display (e.g. 06357), if you have a method to change it, then replace my method name with your own.

Regarding the display, as I'm using a different approach compared to yours, I'm unable to give any help or guide in that aspect.

---

This is my solution:

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController {
    float result;
    IBOutlet UILabel *TextInput;
    int currentOperation;
    float currentNumber;
    BOOL userInTheMiddleOfEnteringDecimal;
}

- (IBAction)buttonDigitPressed:(id)sender;
- (IBAction)buttonOperationPressed:(id)sender;
- (IBAction)cancelInput;
- (IBAction)cancelOperation;
- (IBAction)dotPressed;
@end

Viewcontroller.m

#import "ViewController.h"

@interface ViewController ()


@end

@implementation ViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

- (IBAction)buttonDigitPressed:(id)sender {
    if(!userInTheMiddleOfEnteringDecimal)
    {
        currentNumber = currentNumber*10 + (float)[sender tag];
        TextInput.text = [NSString stringWithFormat:@"%d",(int)currentNumber];
    }
    else{
        TextInput.text= [TextInput.text stringByAppendingString:[NSString stringWithFormat:@"%d",[sender tag]]];
        currentNumber = [TextInput.text floatValue];
    }
}

- (IBAction)buttonOperationPressed:(id)sender {
    if (currentOperation == 0) result = currentNumber;
    else {
        switch (currentOperation) {
            case 1:
                result = result + currentNumber;
                break;
            case 2:
                result = result - currentNumber;
                break;
            case 3:
                result = result * currentNumber;
                break;
            case 4:
                result = result / currentNumber;
                break;
            case 5:
                currentOperation = 0;
                break;
            default:
                break;
        }
    }
    currentNumber = 0;
    TextInput.text = [NSString stringWithFormat:@"%.2f",result];
    if ([sender tag] == 0) result = 0;
    currentOperation = [sender  tag];
    userInTheMiddleOfEnteringDecimal = NO;
}

-(IBAction)cancelInput{
    currentNumber = (int)(currentNumber/10);
    TextInput.text = [NSString stringWithFormat:@"%.2f",currentNumber];;
}

-(IBAction)cancelOperation{
    currentNumber = 0;
    TextInput.text = @"0";
    userInTheMiddleOfEnteringDecimal = NO;
}
- (IBAction)dotPressed{
    if(!userInTheMiddleOfEnteringDecimal){
        userInTheMiddleOfEnteringDecimal = YES;
        TextInput.text= [TextInput.text stringByAppendingString:@"."];
    }
}

@end

Hope this helps.. This includes the decimal point in the button...