Swift 已计算属性模板？

Question

有没有办法对计算属性进行模板化以避免一遍又一遍地重复相同的代码？例如，现在我有一个 class，其中的代码块如下所示：

private var _state:State?
private var _maxs:State?
private var _state1s:State?
private var _state10s:State?

var state:State? {
    get {
        dispatch_semaphore_wait(statephore, DISPATCH_TIME_FOREVER)
        let s=_state
        dispatch_semaphore_signal(statephore)
        return s
    }
    set {
        dispatch_semaphore_wait(statephore, DISPATCH_TIME_FOREVER)
        _state=newValue
        dispatch_semaphore_signal(statephore)
        if newValue != nil {statsTest(newValue!)}
    }
}

var maxs:State? {
    get {
        dispatch_semaphore_wait(maxphore, DISPATCH_TIME_FOREVER)
        let m=_maxs
        dispatch_semaphore_signal(maxphore)
        return m
    }
    set {
        dispatch_semaphore_wait(maxphore, DISPATCH_TIME_FOREVER)
        _maxs=newValue
        dispatch_semaphore_signal(maxphore)
    }
}


var state1s:State? {
    get {
        dispatch_semaphore_wait(state1sphore, DISPATCH_TIME_FOREVER)
        let s=_state1s
        dispatch_semaphore_signal(state1sphore)
        return s
    }
    set {
        dispatch_semaphore_wait(state1sphore, DISPATCH_TIME_FOREVER)
        _state1s=newValue
        dispatch_semaphore_signal(state1sphore)
    }
}

var state10s:State? {
    get {
        dispatch_semaphore_wait(state10sphore, DISPATCH_TIME_FOREVER)
        let s=_state10s
        dispatch_semaphore_signal(state10sphore)
        return s
    }
    set {
        dispatch_semaphore_wait(state10sphore, DISPATCH_TIME_FOREVER)
        _state10s=newValue
        dispatch_semaphore_signal(state10sphore)
    }
}

这里有一个明显的模式，所有重复的代码只是混淆了正在发生的事情并导致错误，因为我 cut/paste/edit/fail。有没有一种方法可以捕获这种模式，然后使用类似以下内容定义我的属性：

var state=ProtectedValue(_state,statephore)

?

Answer 1

这看起来像是泛型和 inout 变量的工作。

func setProtectedValue<T>(inout destination: T, newValue: T, semaphore: SemaphoreType) {
        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER)
        destination = newValue
        dispatch_semaphore_signal(semaphore)
}

在调用站点：

var state10s:State? {
    get {
        //...
    }
    set {
        setProtectedValue(&_state10s, newValue, state10sphore)
    }
}

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