Boolean toggling

Paul Hudson      @twostraws

SE-0199 introduced a new toggle() method to booleans that flip them between true and false..

The entire code to implement proposal is only a handful of lines of Swift:

extension Bool {
   mutating func toggle() {
      self = !self
   }
}

However, the end result makes for much more natural Swift code:

var loggedIn = false
loggedIn.toggle()

As noted in the proposal, this is particularly useful in more complex data structures: myVar.prop1.prop2.enabled.toggle() avoids the potential typing errors that could be caused using manual negation.

The proposal makes Swift easier and safer to write, and is purely additive, so I think most folks will switch to using it quickly enough.

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Other changes in Swift 4.2…

• Derived collections of enum cases
• Warning and error diagnostic directives
• Dynamic member look up
• Enhanced conditional conformances
• Random number generation and shuffling
• Simpler, more secure hashing
• Checking sequence elements match a condition
• In-place collection element removal

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