Swift-Blockchain-New-Block

NewBlock.swift

    
    // MARK: - Initializers
    init() {
        chain = []
        current_transactions = []
        nodes = Set()
        
        // Create the genesis block
        self.newBlock(previous_hash: "1", proof: 100)
    }
    
    
    /**
     # Creates a new block and adds it to the chain
     
     - Parameter proof: <int> The proof given by the Proof of Work algorithm
     - Parameter previous_hash: (Optional) <str> Hash of previous Block
     - returns: _dict_ New Block
     
     */
    func newBlock(previous_hash: String?, proof: Int64) -> Block {
        let block = Block(index: Int64(self.chain.count + 1),
                          timestamp: Date(),
                          transactions: self.current_transactions,
                          proof: proof,
                          previous_hash: previous_hash ?? self.hash(block: self.last_block)
        )
        
        // Reset the current list of transactions
        self.current_transactions = []
        self.chain.append(block)
        
        return block
    }
 
    /**
    Returns the last Block in the chain
     */
    var last_block: Block {
        return self.chain[self.chain.count - 1]
    }
        
    /**
     Creates a SHA-256 hash of a Block
     
     - Parameter block: <dict> Block
     - returns: String
     
     */
    func hash(block: Block) -> String {
        let encoder = JSONEncoder()
        // We must make sure that the Dictionary is Ordered, or we'll have inconsistent hashes
        if #available(OSX 10.13, *) {
            encoder.outputFormatting = .sortedKeys
        }
        
        let str = try! String(data: encoder.encode(block), encoding: .utf8)!
        return str.sha256()
    }