Swift – Read Number from Console Input

To read number from console input in Swift, use readLine() and Int() functions. readLine() function returns the string of characters read from standard input, and Int() converts this string to integer.

Converting to a number is not limited to converting the read string into an integer. We may also use Float(), Double(), etc., to convert the input into desired numeric type.

Examples

In the following example, we read a string from user, convert it into integer, and find its square.

main.swift

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print("Enter a number (x) : ", terminator: "")
if let input = readLine() {
    if let number = Int(input) {
        let result = number * number
        print("You entered \(number)")
        print("Its square = \(result)")
    }
}

Output

Enter a number (x) : 4
You entered 4
Its square = 16!
Program ended with exit code: 0
Enter a number (x) : 3
You entered 3
Its square = 9
Program ended with exit code: 0
Enter a number (x) : -2
You entered -2
Its square = 4
Program ended with exit code: 0

Now, we shall read a string from user, convert it into floating point value, and find its square.

main.swift

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print("Enter a number (x) : ", terminator: "")
if let input = readLine() {
    if let number = Float(input) {
        let result = number * number
        print("You entered \(number)")
        print("Its square = \(result)")
    }
}

Output

Enter a number (x) : 1.2
You entered 1.2
Its square = 1.44
Program ended with exit code: 0

Conclusion

In this Swift Tutorial, we learned how to read a number from user using readLine() function and Int(), Float(), etc., with the help of examples.