how to make Completion Handlers and use it in Swift

Example 1:
no input parameters,just has return like String type

func method1( completion: (result: String) -> Void) {
//some code
completion(“This is method1 result”)
}
Usage:
method1() {
(result: String) in
print(“got back: (result)”)
}

Example 2:
has input parameters,AND has return like String type

func method2(input: String,completion: (result: String) -> Void) {
//some code
completion(“This is method2 result”)
}

Usage: method2(“input parameter value”) { (result: String) in print(“got back: (result)”) }