Swift 5.5 引入了 actor 关键字，用于在并发环境中保护共享的可变状态。它是 Swift Concurrency 中最关键的线程安全工具之一。

actor 类似于 class，但它自动保证其内部的可变状态是线程安全的。它通过序列化访问来防止数据竞争（data race）。

测试结果：

image.png

extension ViewController{
    
    
    func testActor() {
        
     
        
        Task {
            await testActorConcurrency()
        }
    
        Task {
            await testActorConcurrency2()
        }
        
        
        Task {
            await testActorConcurrency3()
        }
        
        
    }
    
    
    func testActorConcurrency() async {
        let counter = Counter()
        let taskCount = 1000

        await withTaskGroup(of: Void.self) { group in
            for _ in 0..<taskCount {
                group.addTask {
                    await counter.increment()
                }
            }
        }

        let final = await counter.getValue()
        print("✅ 最终计数值应为 \(taskCount)，实际为 \(final)")
    }
    
    func testActorConcurrency2() async {
        let counter = Counter2()
        let taskCount = 1000

        await withTaskGroup(of: Void.self) { group in
            for _ in 0..<taskCount {
                group.addTask {
                    await counter.increment()
                }
            }
        }

        let final = await counter.getValue()
        print("✅ 最终计数值应为 \(taskCount)，实际为 \(final)")
    }
    
    func testActorConcurrency3() async {
        let counter = TestClass.Counter()
        let taskCount = 1000

        await withTaskGroup(of: Void.self) { group in
            for _ in 0..<taskCount {
                group.addTask {
                    await counter.increment()
                }
            }
        }

        let final = await counter.getValue()
        print("✅ 最终计数值应为 \(taskCount)，实际为 \(final)")
    }


    
    
}
class Counter2 {
    
     
    private var value = 0

    func increment() {
        value += 1
    }

    func getValue() -> Int {
        return value
    }
}

actor Counter {
    
     
    private var value = 0

    func increment() {
        value += 1
    }

    func getValue() -> Int {
        return value
    }
}



enum TestClass {
    //传统做法
    class Counter {
        private var value = 0
        
        //默认串行线程
        private let queue = DispatchQueue(label: "counter")
        
        func increment() {
            //同步串行
            queue.sync {
                value += 1
            }
        }
        
        func getValue() -> Int {
            //同步串行
            return queue.sync {
                value
            }
        }
    }
    
}