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
Download all Swift 4.2 changes as a playground Link to Swift 4.2 changes
