Converting a hex to string in Swift formatted to keep the same number of digits

Question

I'm trying to create a string from hex values in an array, but whenever a hex in the array starts with a zero it disappears in the resulting string as well.

I use String(value:radix:uppercase) to create the string.

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An example:

Here's an array: [0x13245678, 0x12345678, 0x12345678, 0x12345678].
Which gives me the string: 12345678123456781234567812345678 (32 characters)

But the following array: [0x02345678, 0x12345678, 0x02345678, 0x12345678] (notice that I replaced two 1's with zeroes).
Gives me the string: 234567812345678234567812345678 (30 characters)

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I'm not sure why it removes the zeroes. I know the value is correct; how can I format it to keep the zero if it was there?

Answer 1

The number 0x01234567 is really just 0x1234567. Leading zeros in number literals don't mean anything (unless you are using the leading 0 for octal number literals).

Instead of using String(value:radix:uppercase), use String(format:).

let num = 0x1234567
let str = String(format: "%08X", num)

Explanation of the format:

• The 0 means to pad the left end of the string with zeros as needed.
• The 8 means you want the result to be 8 characters long
• The X means you want the number converted to uppercase hex. Use x if you want lowercase hex.