【Swift】Arrayに検索機能を追加する ref: http://qiita.com/ryokosuge/items/c2c1fbeed297db965529

ArrayExtension.swift

import Foundation

extension Array {

    // 最初に考えついたソースコード
    func find(includeElement: T -> Bool) -> Int? {
        for (index, element) in enumerate(self) {
            if includeElement(element) {
                return index
            }
        }
        return nil
    }
    
}

ArrayExtension_2.swift

extension Array {

    func findAll(includeElement: T -> Bool) -> [(Int, T)] {
        let seq = zip(0..<self.count, self)
        return Swift.filter(seq) { includeElement($0.1) }
    }
    
}

ArrayExtension_3.swift

extension Array {

    func find(includeElement: T -> Bool) -> Int? {
        return Swift.filter(enumerate(self)) { includeElement($0.1) }.first.map { $0.0 }
    }
    
}

Playground.swift

// Playground
class Person {
    var firstName: String
    var lastName: String

    init(firstName: String, lastName: String) {
        self.firstName = firstName
        self.lastName = lastName
    }
}

var hoge = Person(firstName: "hoge", lastName: "hoge")
var fuga = Person(firstName: "fuga", lastName: "fuga")
var hogeFuga = Person(firstName: "hoge", lastName: "fuga")

var persons:[Person] = [hoge, fuga, hogeFuga]

if let hogeIndex = persons.find({ $0 == hoge }) {
    println(hogeIndex)
}