How to split a string by new lines in Swift

Swift 5.2 or later

You can split your String using the new Character property isNewline:

let sentence = "Line 1\nLine 2\nLine 3\n"
let lines = sentence.split(whereSeparator: \.isNewline)
print(lines)   // "["Line 1", "Line 2", "Line 3"]\n"

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You can also extend StringProtocol and create a lines instance property to break up the string lines into subsequences:

extension StringProtocol {
    var lines: [SubSequence] { split(whereSeparator: \.isNewline) }
}

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let sentence = "Line 1\nLine 2\r\nLine 3\n"
for line in sentence.lines {
    print(line)
}
let lines = sentence.lines  // ["Line 1", "Line 2", "Line 3"]

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Original Answer

You can use String method enumerateLines:

Enumerates all the lines in a string.

Swift 3 or later

let sentence = "Line 1\nLine 2\nLine 3\n"
var lines: [String] = []
sentence.enumerateLines { line, _ in
    lines.append(line)
}
print(lines)   // "["Line 1", "Line 2", "Line 3"]\n"

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extension String {
    var lines: [String] {
        var result: [String] = []
        enumerateLines { line, _ in result.append(line) }
        return result
    }
}

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let sentence2 = "Line 4\nLine 5\nLine 6\n"
let sentence2Lines = sentence2.lines
print(sentence2Lines)    // "["Line 4", "Line 5", "Line 6"]\n"
let sentence3 = "Line 7\r\nLine 8\r\nLine 9\r\n"
let sentence3Lines = sentence3.lines
print(sentence3Lines)  // "["Line 7", "Line 8", "Line 9"]\n"