swift - 如何在 Swift Perfect 框架中锁定/解锁变量

Question

如何在 Swift Perfect 框架中锁定 var transactions，以避免在我删除函数 storeTransactions() 中的所有项目之前由其他线程插入新事务:

class Foo {
    var transactions: [Transaction] = []

    func storeTransactions() {
        let transactionStogare = Storage(transactions: self.transactions)
        // <-- Some thread can append new transaction in this moment
        self.transactions = []
        // TODO: do something with transactionStogare
    }

    func appendTransaction(t: Transaction) {
        self.transactions.append(t)
    }
}

请记住，该解决方案也应该适用于 Linux。

Answer 1

你应该:

import PerfectThread

这为您提供了许多由框架本身实现的线程实用程序(因此，它在 Linux 和 macOS 上都可以处理)

在您的情况下，您希望从多个线程读取“共享数据”，但在写入时，它必须等待其他读/写线程完成其工作。您将使用 Threading.RWLock。

你可以这样做:

class TransactionContainer {
    let lock = Threading.RWLock()
    private var _transactions: [Transactions]

    var transactions: [Transactions] {
        get {
            defer { // This is done after return
                lock.unlock()
            }
            lock.readLock() // Make a "read" lock, which permits
                            //  multiple reads, but no concurrent
                            //  writing.
            return _transactions
        }
        set(value) {
            lock.doWithWriteLock { // Do a write lock, which
                                   //   doesn't permit concurrent writing
                                   //   nor concurrent reading.
                                   // This is an easier expression than
                                   //   using defer and lock.unlock()
                                   //   but can't be used for returning
                                   //   because it is closure
                self._transactions = value
            }
        }
    }
}