are self-contained blocks of functionality that can be passed around and used in your code.
But what does that actually mean? (Basically they are aware of their surroundings!😲 ) this can be a very powerful tool!
//Lets look at this example
// e.g. 7
// We have n array of ages in an unordered list
let listOfAge = [1, 32, 3, 66, 31, 64, 9, 22]
// We can use an inbuilt Swift method called sorted(by:) to sort the order
// sorted(by:) method doesn't alter the existing array it returns a new one
// A - pass in the function
func backward(_ i1: Int, _ i2: Int) -> Bool {
return i1 < i2
}
var ascendingAge = listOfAge.sorted(by: backward)
print("list of \(ascendingAge)")
// ascendingAge is equal to ["Ewa", "Daniella", "Chris", "Barry", "Alex"]
// B - use closure expression syntax
ascendingAge = listOfAge.sorted(by: { (i1: Int, i2: Int) -> Bool in
return i1 < i2
})
// C - refactor as Swift infers type from Context
// Because Swift infers the types of the parameters and return value
// i.e. it takes (Int, Int) -> Bool and returns Bool
// we can simplify the closure further
ascendingAge = listOfAge.sorted(by: { i1, i2 in return i1 < i2 })
// D - refactor further using shorthand argument names & Operator Methods
// Swift provides shorthand argument names to inline closures, hence we can access arguments using $0, $1, $2 etc...
ascendingAge = listOfAge.sorted(by: { $0 < $1 })
// There is an even shorter way to write this as the return value from
// closure matches the exact method provided by sorted(by:)
// i.e. two Int parameters and returns a Bool
ascendingAge = listOfAge.sorted(by: <)These are just the absolute basics that will be required, We recommend you read through the Language Guide