[Swift extensions] #iOS

ArrayExtensions.swift

public extension Array {

    /// Secure access at index.
    ///
    /// let array = [1, 2]
    /// array[safe: 0] // Optional(1)
    /// array[safe: 1] // Optional(2)
    /// array[safe: 2] // nil
    subscript (safe index: Index) -> Element? {
        return indices.contains(index) ? self[index] : nil
    }

    /// Set the value to the beginning of the array.
    ///
    /// [2, 3, 4, 5].prepend(1) -> [1, 2, 3, 4, 5]
    public mutating func prepend(_ newElement: Element) {
        insert(newElement, at: 0)
    }

    /// first vs second.
    public var second: Element? {
        return self[safe: 1]
    }
}

IntExtensions.swift

extension Int {

    /// Comma notation separated by three digits 1000000 -> 1,000,000
    public var commaFormatted: String {
        if self < 0 {
            return "0"
        }
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        let commaString = formatter.string(from: self as NSNumber)
        return commaString ?? "\(self)"
    }
}