swift - how to check if an array contains nth time a string?

Question

let's take the array :

var myArray = ["a", "b", "c", "a", "b", "a", "b", "c", "a", "b"]

I know that you need to use .contains() to know if the array contains an objet. myArray.contains("a") //true

But how to know if the array contains 4 times "a" ?

Answer 1

In Swift this can be find out with just a single line of code :

myArray.filter{$0 == "a"}.count 

Hope it helps. Enjoy Coding

Answer 2

The filter solution shown in other answers is neat, and fit for the purpose. I'll include a few more alternatives.

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As another alternative, use a simple for ... in loop with a where condition holding the conditional to increase a counter:

let myArray = ["a", "b", "c", "a", "b", "a", "b", "c", "a", "b"]
var count = 0
for element in myArray where element == "a" { count += 1 }
print(count) //4

Or, as another alternative, make use of reduce:

let myArray = ["a", "b", "c", "a", "b", "a", "b", "c", "a", "b"]
let count = myArray.reduce(0) { $0 + ($1 == "a" ? 1 : 0) }
print(count) //4

I'll also include a use example for NSCounted set covered in @user28434's answer

import Foundation
let myArray = ["a", "b", "c", "a", "b", "a", "b", "c", "a", "b"]
let countedSet = NSCountedSet(array: myArray)
let count = countedSet.count(for: "a")
print(count) // 4

// or, simply
let count = NSCountedSet(array: myArray).count(for: "a")