CollectionExtensions.swift

import Foundation

struct Foobar<T: Equatable> {
    let value: T
    let count: Int
}

extension Collection {
    func sumOfCounts<T>(where predicate: (T) -> Bool) -> Int where Element == Foobar<T> {
        reduce(0, { $0 + (predicate($1.value) ? $1.count : 0) })
    }

    func printAll<T>() where Element == Foobar<T> {
        forEach({ e in print(e.value) })
    }
}

let array = [
    Foobar<String>(value: "one", count: 1),
    Foobar<String>(value: "two", count: 2),
    Foobar<String>(value: "three", count: 3),
]

array.printAll()
array.sumOfCounts(where: { $0.contains("one") })

let aa: [String?] = [
    "", nil, "1"
]

extension Array {
    func filterNil<T>() -> [T] where Element == Optional<T> {
        compactMap({ $0 })
    }
}

aa.filterNil()

protocol OptionalType {
    associatedtype Wrapped
    var value: Wrapped? { get }
}

extension Optional: OptionalType {
    var value: Wrapped? { self }
}

extension Array where Element: OptionalType {
    func filterShit() -> [Element.Wrapped] {
        compactMap({ $0.value })
    }
}

aa.filter

Inspired from: https://twitter.com/jegnux/status/1259936037721292800