Question

有没有办法模拟计算属性，以避免反复重复相同的代码？例如，现在我有一个类，其代码块如下所示：

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模糊了正在发生的事情，并在剪切/粘贴/编辑/失败时导致错误。有没有办法可以捕获这个模式，然后用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)
}

在通话网站：

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

Swift计算属性模板？

1 个答案: