.swift

class Block : Codable  {
    
    var index :Int = 0
    var previousHash :String = ""
    var hash :String!
    var nonce :Int
    
    private (set) var transactions :[Transaction] = [Transaction]()
    
    var key :String {
        get {
            
            let transactionsData = try! JSONEncoder().encode(self.transactions)
            let transactionsJSONString = String(data: transactionsData, encoding: .utf8)
            
            return String(self.index) + self.previousHash + String(self.nonce) + transactionsJSONString!
        }
    }
    
    func addTransaction(transaction :Transaction) {
        self.transactions.append(transaction)
    }
    
    init() {
        self.nonce = 0
    }
    
}