Finding out whether a string is numeric or not

Question

How can we check if a string is made up of numbers only. I am taking out a substring from a string and want to check if it is a numeric substring or not.

NSS         


        

Answer 1

Yet another option:

- (BOOL)isValidNumber:(NSString*)text regex:(NSString*)regex {
    @try {
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
        return [predicate evaluateWithObject:text];
    }
    @catch (NSException *exception) {
        assert(false); 
        return NO;
    }
}

Usage example:

BOOL isValid = [self isValidNumber:@"1234" regex:@"^[0-9]+$"];

Answer 2

For Swift 3

var onlyDigits: CharacterSet = CharacterSet.decimalDigits.inverted
if testString.rangeOfCharacter(from: onlyDigits) == nil {
  // String only consist digits 0-9
}

Answer 3

Test if a string is a number Might be Helpful

int i = [@"12.3" rangeOfCharacterFromSet: [ [NSCharacterSet characterSetWithCharactersInString:@"0123456789."] invertedSet] ].location;

if (i == NSNotFound) {
     //is a number
}

Answer 4

Simple wrote the string extension:

extension String {
    var isNumeric: Bool {
        return self.rangeOfCharacter(from: CharacterSet.decimalDigits.inverted) == nil
    }
}

Answer 5

An extension of @John Calsbeek's answer, and clarification of @Jeff and @gyratory circus's comments.

+ (BOOL)doesContainDigitsOnly:(NSString *)string
{
    NSCharacterSet *nonDigits = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];

    BOOL containsDigitsOnly = [string rangeOfCharacterFromSet:nonDigits].location == NSNotFound;

    return containsDigitsOnly;
}

+ (BOOL)doesContainNonDigitsOnly:(NSString *)string
{
    NSCharacterSet *digits = [NSCharacterSet decimalDigitCharacterSet];

    BOOL containsNonDigitsOnly = [string rangeOfCharacterFromSet:digits].location == NSNotFound;

    return containsNonDigitsOnly;
}

The following can be added as category methods for NSString

- (BOOL)doesContainDigitsOnly
{
    NSCharacterSet *nonDigits = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];

    BOOL containsDigitsOnly = [self rangeOfCharacterFromSet:nonDigits].location == NSNotFound;

    return containsDigitsOnly;
}

- (BOOL)doesContainNonDigitsOnly
{
    NSCharacterSet *digits = [NSCharacterSet decimalDigitCharacterSet];

    BOOL containsNonDigitsOnly = [self rangeOfCharacterFromSet:digits].location == NSNotFound;

    return containsNonDigitsOnly;
}

Answer 6

The easiest and most reliable way is trying to cast as Double, if the result is nil - it can't be formed into a legit number.

let strings = ["test", "123", "123.2", "-123", "123-3", "123..22", ".02"]
let validNumbers = strings.compactMap(Double.init)

print(validNumbers)
// prints [123.0, 123.2, -123.0, 0.02]

More info in the documentation: https://developer.apple.com/documentation/swift/double/2926277-init