Array utility functions

Array + Util.swift

import Foundation

// MARK: - Array
public extension Array {
    
    /// Safe subscript for element at index
    ///
    /// - Parameter index: array's index to subscript.
    /// - Returns: Optional array element if it exists in that index.
    public func item(at index: Int) -> Element? {
        guard count > index else { return nil }
        guard index >= 0 else { return nil }
        return self[index]
    }
    
    /// Picks random elements from the array. Accepts duplicates.
    ///
    /// - Parameter amount: elements count to be picked randomly.
    public subscript (randomPick amount: Int) -> [Element] {
        
        var random = [Element]()
        for _ in 0..<amount {
            let indexToSelect = Int(arc4random_uniform(UInt32(count - 1)))
            let element = self[indexToSelect]
            random.append(element)
        }
        return random
    }
    
    /// Keeps the last 'n' items in the array.
    ///
    /// - Parameters:
    ///   - maxCount: maximum amount of elements the array should keep.
    public func keepLast(_ maxCount: Int) -> Array {
        return Array(suffix(maxCount))
    }

    /// Generates a new array with a shifted starting point.
    ///
    /// - Parameter positions: Amount of elements to shift.
    /// - Returns: New array with shifted elements.
    public func shifted(_ positions: Int) -> Array {
        var result = self[positions..<self.count]
        result += self[0..<positions]
        return Array(result)
    }

    /// Splits the array in multiple arrays.
    ///
    /// - Parameter size: Size of the sub arrays
    /// - Returns: Array of Arrays.
    public func chunks(size: Int) -> [[Element]] {
        return stride(from: 0, to: count, by: size).map {
            let range = $0..<Swift.min($0 + size, count)
            return Array(self[range])
        }
    }
}