Swift `in` keyword meaning?
Closure expression syntax has the following general form:
In a named function, we declare the parameters and return type in the func
declaration line.
func say(s:String)->() {
// body
}
In an anonymous function, there is no func
declaration line - it's anonymous! So we do it with an in
line at the start of the body instead.
{
(s:String)->() in
// body
}
(That is the full form of an anonymous function. But then Swift has a series of rules allowing the return type, the parameter types, and even the parameter names and the whole in
line to be omitted under certain circumstances.)