FlatMap magic with optionals

flatmap-magic.swift

var number: Int?

number.flatMap {
	// this is never executed
	print($0)
}

number = 1

number.flatMap {
	// this is executed!
	print($0)
}


// Same with closures
// ---------

var closure: (() -> ())?

closure.flatMap {
	// this is never executed
	$0()
}

// Set value
closure = {
	print("hello flatMap")
}

closure.flatMap {
	// this is now ejecuted!
	$0()
}


// So, instead of "if" or "if let" with optionals, you can flatMap them

// Instead of this...
if let n = number {
	// use n
}

// You can do this...
number.flatMap {
	// use $0
	print($0)
}

// It's even better if you need to call a function when the value is not nil

func my_function(n: Int) {
	// bla bla bla
}

// Instead of this...
if let n = number {
	my_function(n)
}

// You can do this (call the function only when there's a value)
number.flatMap(my_function)


// Same with closures...
// ------------

if let c = closure {
	// use c()
}

closure.flatMap {
	$0()
}

// Btw, for closures, you have a better shortcut:

closure?()