Regex replace spaces at each new lines

Question

I am saving users input to db as a string and I would like to remove all spaces at each lines.

Input from user:

Hi!

My name is:
   Bob

I am from the USA.

I want to remove spaces between "Bob", so the result will be:

Hi!

My name is:
Bob

I am from the USA.

I am trying to do it with the following code

let regex = try! NSRegularExpression(pattern: "\n[\\s]+", options: .caseInsensitive)
a = regex.stringByReplacingMatches(in: a, options: [], range: NSRange(0..<a.utf16.count), withTemplate: "\n")

but this code replace multiple new lines "\n", I don't want to do it. After I run the above code: "1\n\n\n 2" -> "1\n2". The result I need: "1\n\n\n2" (only spaces are removed, not new lines).

Answer 1

No need for regex, split the string on the new line character into an array and then trim all lines and join them together again

let trimmed = string.components(separatedBy: .newlines)
    .map { $0.trimmingCharacters(in: .whitespaces) }
    .joined(separator: "\n")

or you can use reduce

let trimmed = string.components(separatedBy: .newlines)
    .reduce(into: "") { $0 += "\($1.trimmingCharacters(in: .whitespaces))\n"}
    

Answer 2

You can use

let regex = try! NSRegularExpression(pattern: "(?m)^\\h+", options: .caseInsensitive)

Actually, as there are no case chars in the pattern, you may remove .caseInsensitive and use:

let regex = try! NSRegularExpression(pattern: "(?m)^\\h+", options: [])

See the regex demo. The pattern means:

• (?m) - turn on multiline mode
• ^ - due to (?m), it matches any line start position
• \h+ - one or more horizontal whitespaces.

Swift code example:

let txt = "Hi!\n\nMy name is:\n   Bob\n\nI am from the USA."
let regex = "(?m)^\\h+"
print( txt.replacingOccurrences(of: regex, with: "", options: [.regularExpression]) )

Output:

Hi!

My name is:
Bob

I am from the USA.