How do I change the number of decimal places iOS?

问题

I have a simple calculator app and I want it to be so that if the answer requires no decimal places, there are none, just whole numbers. If the answer was 2, I don't want it to say 2.000000, it should say 2. If it requires one decimal place, it should show to one decimal place for example 12.8 instead of 12.80. How would I do this? Here is my code. btw, this is from a tutorial at http://www.youtube.com/watch?v=Ihw0cfNOrr4, not my own work.

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:
       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;

}

回答1:

One way is to use NSNumberFormatter to format your result instead of NSString's -stringWithFormat::

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setMaximumFractionDigits:requiredDigits];
[formatter setMinimumFractionDigits:0];
NSString *result = [formatter stringFromNumber:[NSNumber numberWithFloat:currentNumber];

回答2:

The easiest way is just use [[NSNumber numberWithFloat:] stringValue]

Example:

float someFloatValue;
NSString floatWithoutZeroes = [[NSNumber numberWithFloat:someFloatValue] stringValue];

回答3:

If we use %g in place of %f will truncate all zeros after decimal point.

For example

[NSString stringWithFormat:@"%g", 1.201000];

Output

1.201

回答4:

This should work

NSString *result = [@(currentNumber) description];

回答5:

I had the same problem. This is the code snippet that solved it (looks a lot like Caleb's solution, but that one didn't work for me, so I had to add an extra line):

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
numberFormatter.numberStyle = kCFNumberFormatterDecimalStyle;
numberFormatter.maximumFractionDigits = 20;
numberFormatter.minimumFractionDigits = 0;

NSNumber *number = [[NSNumber alloc]init];
NSString *numberString = [numberFormatter stringFromNumber:number];

We can use another numberStyle and override its basic appearance, setting desired properties of an NSNumberFormatter.

来源：https://stackoverflow.com/questions/7531095/how-do-i-change-the-number-of-decimal-places-ios

标签

ios

xcode

calculator