76899

How to split a string at the last occurence of a sequence

Target: A string with a built-in separator shall be split in an int and another string. In the case that the separator sequence '###' occurs more than once, the string shall always be spliced at the last '###'.

Is there an operator like string.lastIndexOf("###"), like in C#?

This is how my parser looks like:

func parseTuple(from string: String) -> (String, Int)? { let parsedString = string.components(separatedBy: "###") if let tupleString = String(parsedString[0]), let tupleInt = Int(parsedString[1]) { return (tupleString, tupleInt) } else { return nil } }

Answer1:

The range(of:...) method of String has a .backwards option to find the last occurrence of a string. Then substring(to:) and substring(from:) can be used with the lower/upper bound of that range to extract the parts of the string preceding/following the separator:

func parseTuple(from string: String) -> (String, Int)? { if let theRange = string.range(of: "###", options: .backwards), let i = Int(string.substring(from: theRange.upperBound)) { return (string.substring(to: theRange.lowerBound), i) } else { return nil } }

Example:

if let tuple = parseTuple(from: "Connect###Four###Player###7") { print(tuple) // ("Connect###Four###Player", 7) } <hr>

<strong>Swift 4 update:</strong>

func parseTuple(from string: String) -> (String, Int)? { if let theRange = string.range(of: "###", options: .backwards), let i = Int(string[theRange.upperBound...]) { return (String(string[...theRange.lowerBound]), i) } else { return nil } }

Answer2:

let input = "Connect###Four###Player###7" let seperator = "###" // split components var components = input.components(separatedBy: seperator) // remove the last component ... components = Array(components.dropLast()) // ... and re-join the remaining ones let output = components.joined(separator: seperator) print(output)

prints:

Connect###Four###Player

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