check string is int or double , with extension in swift 3

Question

I have string extension you can see under below but only returns true for Int , I want to return it true, for All , Int and Double values only.

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

How can I fix it ? Any idea ? ty.

Just check if the string can be *converted* to an Int or a Double. See for example https://stackoverflow.com/a/30315832/1187415. — Martin R, May 29 '17 at 12:56
@NiravD what ? , I want to check only string if int or double must be return true if not , must be false — SwiftDeveloper, May 29 '17 at 13:05

vacawama · Accepted Answer · 2017-05-29T13:52:49.387

As @MartinR said, check if the string can be converted to an Int or a Double:

extension String  {
    var isnumberordouble: Bool { return Int(self) != nil || Double(self) != nil }
}

print("1".isnumberordouble)      // true
print("1.2.3".isnumberordouble)  // false
print("1.2".isnumberordouble)    // true

@MartinR raises a good point in the comments. Any value that converts to an Int would also convert to a Double, so just checking for conversion to Double is sufficient:

extension String  {
    var isnumberordouble: Bool { return Double(self) != nil }
}

Handling leading and trailing whitespace

The solution above works, but it isn't very forgiving if your String has leading or trailing whitespace. To handle that use the trimmingCharacters(in:) method of String to remove the whitespace (requires Foundation):

import Foundation

extension String  {
    var isnumberordouble: Bool { return Double(self.trimmingCharacters(in: .whitespaces)) != nil }
}

print("  12 ".isnumberordouble)     // true

Checking for Double might be sufficient... A string representing an integer should also be a valid double. — Martin R, May 29 '17 at 13:25

check string is int or double , with extension in swift 3

1 Answers1