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Updated for Xcode 15
Closures in Swift have a distinct syntax that really separates them from simple functions, and one place that can cause confusion is how we accept and return parameters.
First, here’s a closure that accepts one parameter and returns nothing:
let payment = { (user: String) in
print("Paying \(user)…")
}
Now here’s a closure that accepts one parameter and returns a Boolean:
let payment = { (user: String) -> Bool in
print("Paying \(user)…")
return true
}
If you want to return a value without accepting any parameters, you can’t just write -> Bool in
– Swift won’t understand what you mean. Instead, you should use empty parentheses for your parameter list, like this:
let payment = { () -> Bool in
print("Paying an anonymous person…")
return true
}
If you think about it, that works just the same as a standard function where’d write func payment() -> Bool
.
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