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Category: Swift

Reading text files with arbitrary line endings in Swift 3

Published November 21, 2016

It’s easy enough in Swift to get an array of strings representing the lines of a text file:

  let contents = try! String(contentsOf: textFileURL)
  let lines = contents.components(separatedBy: .newlines)

…but what if the input might be a DOS format text file? CharacterSet.newlines contains both "\r" and "\n", so the code above will divide the text at each of them, and the array of strings will contain an extra empty string between every line.

Turns Out™ that Foundation has a number of APIs that understand all the ways line endings are represented in text files. The easiest way to read a text file with arbitrary line endings is to use the enumerateSubstrings(in:options:body:) method, specifying EnumerationOptions.byLines. This uses getLineStart(_:end:contentsEnd:for:) to recognize the line endings (see the documentation thereof for details) and is powerful enough to handle files with mixed line endings.

(In Objective-C these are the -enumerateSubstringsInRange:options:usingBlock: and -getLineStart:end:contentsEnd:forRange: methods of NSString.)

It’s straightforward to wrap this into an extension on String:


extension String {
func separatedIntoLines() -> [String] {
var lines: [String] = []
let wholeString = self.startIndex..<self.endIndex
self.enumerateSubstrings(in: wholeString, options: .byLines) {
(substring, range, enclosingRange, stopPointer) in
if let line = substring {
lines.append(line)
}
}
return lines
}
}

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String+SeparatedIntoLines.swift

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The name separatedIntoLines() seems like the best choice to describe the work being done; the alternative of a computed property simply called lines seems a little too terse to me. UPDATE 2018-02-13: After reviewing the Swift 4 API, perhaps splitIntoLines() would be a better name.

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VisualEffectPlayground in Swift

Published April 22, 2016

When searching for information on implementing vibrancy effects and NSVisualEffectView, developers often find references to the VisualEffectPlayground sample code presented by Apple at WWDC 2014. However, they soon quickly discover that Apple pulled the sample code from the Apple Developer site. Perhaps the application was thrown together for WWDC and didn’t meet the usual standard for Apple sample code; however, to date Apple has not seen fit to post any replacement. And so the search continues.

During my own search, I discovered that a Xamarin engineer named Oleg Demchenko had ported the sample code to Mono and posted it to the Xamarin samples site. In order to get a working sample application, I decided to port this code back to Swift and posted it to GitHub.

DISCLAIMER: I don’t know C# and I’m still learning Swift. Nevertheless, the resulting application appears to perform as expected (although I haven’t made an exhaustive test). I will certainly consider any pull requests.

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Updating the cover of the Swift iBook

Published June 17, 2014

Apple updated the cover of The Swift Programming Language to match the new book in the series, but deleting and redownloading the book within iBooks in OS X Mavericks didn’t update the cover — it continued to display the original cover.

The solution was to quit iBooks, delete the iBooks cache located at ~/Library/Containers/com.apple.iBooksX/Data/Library/Caches/com.apple.iBooksX, and restart iBooks.

You’re welcome, Internet.

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