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We’ve been using () -> Void
to mean “accepts no parameters and returns nothing”, but you can replace that Void
with any type of data to force the closure to return a value.
To demonstrate this, we can write a travel()
function that accepts a closure as its only parameter, and that closure in turn accepts a string and returns a string:
func travel(action: (String) -> String) {
print("I'm getting ready to go.")
let description = action("London")
print(description)
print("I arrived!")
}
Now when we call travel()
using trailing closure syntax, our closure code is required to accept a string and return a string:
travel { (place: String) -> String in
return "I'm going to \(place) in my car"
}
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