Filter out null character strings from string array

Question

I receive a json array of strings from an external source and some of my string look like

"\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00"

I would like to filter out all strings that only contain these null values. I've tried this

arr = arr.filter { (str: String) -> Bool in
            let invalid = String(data: Data.init(count: str.count), encoding: String.Encoding.utf8)
            print(str)

            return str == invalid
        }

Since these are all null terminators, i decided to create a null string of the same length as str but only containing null terminators and compare them.

But this doesn't work. Any help will be appreciated.

Are you sure those are null terminators? It seems like the backslash character, followed by x followed by 2 zeros. — Sweeper
– Sweeper, Commented Jul 24, 2018 at 0:38
You are right. These are not null terminators. Not sure why i am getting that string for the external source. Guess i'd have to figure that out — SomeGuyFortune
– SomeGuyFortune, Commented Jul 24, 2018 at 3:05

Sweeper · Accepted Answer · 2018-07-24 00:51:08Z

2

I don't think those are null terminators because the backslashes are escaped. Those are just the four character sequence \x00 repeated multiple times.

To match such a pattern, you can use regular expressions:

let regex = try! NSRegularExpression(pattern: "^(?:\\\\x00)+$", options: [])
let string = "\\x00\\x00\\x00\\x00\\x00"
// the below will evaluate to true if the string is full of \x00
regex.firstMatch(in: string, options: [], range: NSRange(location: 0, length: string.count)) != nil

answered Jul 24, 2018 at 0:51

Sweeper

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