What is CompactMap operator in Swift Combine?

import UIKit

import Combine

var cancellable: AnyCancellable!

let dictionary: [Int : String] = [1: "One", 2: "Two", 3: "Three", 5: "Five"]

let numbers = (0...5)

cancellable = numbers.publisher

    .sink { numberKey in

        print(dictionary[numberKey])

    }

The result of above code :

nil

Optional("One")

Optional("Two")

Optional("Three")

nil

Optional("Five")

I want to unwrap value and this is the time to use CompactMap operator.

Let's add CompactMap operator to above code

import UIKit

import Combine

var cancellable: AnyCancellable!

let dictionary: [Int : String] = [1: "One", 2: "Two", 3: "Three", 5: "Five"]

let numbers = (0...5)

cancellable = numbers.publisher

    .compactMap({ numberKey -> String? in

        return dictionary[numberKey]

    })

    .sink { value in

        print(value)

    }

The result of above code :

One

Two

Three

Five

So, CompactMap operator is useful to unwrap optional value

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