在 iOS 中实现区块链

blockchain.swift

import Cocoa
import Foundation

class Block {
    var index: Int = 0
    var dateCreated: String
    var previousHash: String!
    var hash: String!
    var nonce: Int
    
    var key: String {
        get {
            return String(self.index) + self.dateCreated + self.previousHash + String(self.nonce)
        }
    }
    
    init() {
        self.dateCreated = Date().toString()
        self.nonce = 0
    }
}

class Blockchain {
    private (set) var blocks = [Block]()
    
    init(_ genesisBlock: Block) {
       addBlock(genesisBlock)
    }
    
    func addBlock(_ block: Block) {
        if blocks.isEmpty {
            // 添加创世区块
            // 第一个区块没有 previous hash
            block.previousHash = "0"
            block.hash = generateHash(for: block)
        } else {
            let previousBlock = getPreviousBlock()
            block.previousHash = previousBlock.hash
            block.index = blocks.count
            block.hash = generateHash(for: block)
        }
        
        blocks.append(block)
        displayBlock(block)
    }
    
    private func getPreviousBlock() -> Block {
        return blocks[blocks.count - 1]
    }
    
    private func displayBlock(_ block: Block) {
        print("------ 第 \(block.index) 个区块 --------")
        print("创建日期：\(block.dateCreated)")
        print("Nonce：\(block.nonce)")
        print("前一个区块的哈希值：\(block.previousHash!)")
        print("哈希值：\(block.hash!)")
    }
    
    private func generateHash(for block: Block) -> String {
        var hash = block.key.sha1Hash()
        while !hash.hasPrefix("00") {
            block.nonce += 1
            hash = block.key.sha1Hash()
        }
        return hash
    }
}

// String extension
extension String {
    func sha1Hash() -> String {
        let task = Process()
        task.launchPath = "/usr/bin/shasum"
        task.arguments = []
        
        let inputPipe = Pipe()
        
        inputPipe.fileHandleForWriting.write(self.data(using: .utf8)!)
        
        inputPipe.fileHandleForWriting.closeFile()
        
        let outputPipe = Pipe()
        task.standardOutput = outputPipe
        task.standardInput = inputPipe
        task.launch()
        
        let data = outputPipe.fileHandleForReading.readDataToEndOfFile()
        let hash = String(data: data, encoding: .utf8)!
        return hash.replacingOccurrences(of: "  -\n", with: "")
    }
}

extension Date {
    func toString() -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
        return formatter.string(from: self)
    }
}

let block1 = Block()
let blockchain = Blockchain(block1)

for index in 1...5 {
    let block = Block()
    blockchain.addBlock(block)
}

新建 playground 时选择 macOS！