The lazy
keyword has always allowed us to write stored properties that are only calculated when first used, but from Swift 5.5 onwards we can use lazy
locally inside a function to create values that work similarly.
This code demonstrates local lazy
in action:
func printGreeting(to: String) -> String {
print("In printGreeting()")
return "Hello, \(to)"
}
func lazyTest() {
print("Before lazy")
lazy var greeting = printGreeting(to: "Paul")
print("After lazy")
print(greeting)
}
lazyTest()
When that runs you’ll see “Before lazy” and “After lazy” printed first, followed by “In printGreeting()” then “Hello, Paul” – Swift only runs the printGreeting(to:)
code when its result is accessed on the print(greeting)
line.
In practice, this feature is going to be really helpful as a way of selectively running code when you have conditions in place: you can prepare the result of some work lazily, and only actual perform the work if it’s still needed later on.
SPONSORED AppSweep by Guardsquare helps developers automate the mobile app security testing process with fast, free scans. By using AppSweep’s actionable recommendations, developers can improve the security posture of their apps in accordance with security standards like OWASP.
Sponsor Hacking with Swift and reach the world's largest Swift community!
Download all Swift 5.5 changes as a playground Link to Swift 5.5 changes
Link copied to your pasteboard.