Delete non alphabetic characters at the starting of String - ios

Question

I want to replace all the non-alphanumeric characters (including white spaces) of a string up to the first alphabet
"\r\n A Simple PDF File \r\n This is a small demonstration .pdf file - \r\n just for use in the Virtual Mechanics tutorials. More text. And more \r\n text."
I used
let string = txtView.text
let newString = string.replacingOccurrences(of: "\n", with: "")
but it replaces all the "\n" of string. how could we replace the starting characters only?

Answer 1

I am able to remove leading white spaces using regular expression. This is the code :
extension String {
func trimLeadingWhitespaces() -> String {
return self.replacingOccurrences(of: "^\\s+", with: "", options: .regularExpression)
}
}
let string = " Some string abc"
let trimmed = string.trimLeadingWhitespaces()
print(trimmed)

Answer 2

There is a function drop that removes characters while a condition is filled.
Here are two variants of using it
let newString = string.drop { $0.isWhitespace || $0.isPunctuation }
let newString = string.drop { !($0.isLetter || $0.isNumber) }

Answer 3

You can use trimmingCharacters method of string class. It will remove all the leading and trailing whitespaces and \n from string.
let str = "\r\n A Simple PDF File \r\n This is a small demonstration .pdf file - \r\n just for use in the Virtual Mechanics tutorials. More text. And more \r\n text."
let result = str.trimmingCharacters(in: .whitespacesAndNewlines)
print(result)

Answer 4

Only leading spaces:
extension String {
func removingLeadingSpaces() -> String {
guard let index = firstIndex(where: { !CharacterSet(charactersIn: String($0)).isSubset(of: .whitespaces) }) else {
return self
}
return String(self[index...])
}
}

Answer 5

you can use two func from extension (thx #amer):
extension String {
func replacingFirstOccurrence(of string: String, with replacement: String) -> String {
guard let range = self.range(of: string) else { return self }
return replacingCharacters(in: range, with: replacement)
}
func removingLeadingSpaces() -> String {
guard let index = firstIndex(where: { !CharacterSet(charactersIn: String($0)).isSubset(of: .whitespaces) }) else {
return self
}
return String(self[index...])
}
}
and use it:
let myString = "\r\n A Simple PDF File \r\n This is a small demonstration .pdf file - \r\n just for use in the Virtual Mechanics tutorials. More text. And more \r\n text."
let charactersRemoved = myString.replacingFirstOccurrence(of: "\r\n", with: "")
let whiteSpacesRemoved = charactersRemoved.removingLeadingSpaces()
print(whiteSpacesRemoved) // "A Simple PDF File \r\n This is a small demonstration .pdf file - \r\n just for use in the Virtual Mechanics tutorials. More text. And more \r\n text."

Answer 6

[ |\t|\n|\r] matchs for space, newline, tabulation or carriage return
{2,} "2 times or more"
each match is replaced with a newline
let str = "\r\n A Simple PDF File \r\n This is a small demonstration .pdf file - \r\n just for use in the Virtual Mechanics tutorials. More text. And more \r\n text."
let newString = str.replacingOccurrences(
of: "[ |\t|\n|\r]{2,}",
with: "\n",
options: .regularExpression
)
print(newString)
// A Simple PDF File
// This is a small demonstration .pdf file -
// just for use in the Virtual Mechanics tutorials. More text. And more
// text.

Answer 7

As per your problem statement you need to delete non-alphabetic char which includes spaces, line,'#','$','%','^', etc. There is much non-alphabetic char. Instead of checking non-alphabetic char , you chan validate alphabetic char alone. Please check the following solution to your problem.
extension String{
func findFirstAlphabetic() -> String.Index?{
for index in self.indices{
if String(self[index]).isAlphanumeric == true{
return index
}
}
return nil
}
var isAlphanumeric: Bool {
return !isEmpty && range(of: "[^a-zA-Z0-9]", options: .regularExpression) == nil
}
func alphabetic_Leading_SubString() -> String?{
if let startIndex = self.findFirstAlphabetic(){
let newSubString = self[startIndex..<self.endIndex]
return String(newSubString)
}
return nil
}
}
usage:-
print("Output" + string.alphabetic_Leading_SubString())
Input :-
let string = "\r\n# # $ % & ^ * () -+ ######## A Simple PDF File \r\n This is a small demonstration .pdf file - \r\n just for use in the Virtual Mechanics tutorials. More text. And more \r\n text."
Output:-