Swift:如何在不调用其 didSet 函数的情况下更改属性的值

Question

如何在 Swift 中设置一个属性的值，而不用在初始化上下文之外调用它的 didSet() 函数？下面的代码是在类的 noside() 函数

中实现此目的的失败实验

class Test
{
    var toggle : Bool = 0
    var hoodwink : Int = 0 {
        didSet(hoodwink)
        {
            toggle = !toggle
        }
    }

// failed attempt to set without a side effect

    func noside(newValue : Int)
    {
        hoodwink = newValue
        println("hoodwink: \(hoodwink) state: \(toggle)")
    }

    func withside(newValue : Int)
    {
        self.hoodwink = newValue
        println("hoodwink: \(hoodwink) state: \(toggle)")
    }
}

在 Objective-C 中使用自动合成的属性是很简单的:

有副作用(如果存在于 setter 中):

self.hoodwink = newValue;

无副作用:

_hoodwink = newValue;

Answer 1

一个可能的破解方法是提供一个绕过 didSet 的 setter

 var dontTriggerObservers:Bool = false
    var selectedIndexPath:NSIndexPath? {
        didSet {
            if(dontTriggerObservers == false){
                //blah blah things to do
            }
        }
    }
    var primitiveSetSelectedIndexPath:NSIndexPath? {
        didSet(indexPath) {
            dontTriggerObservers = true
            selectedIndexPath = indexPath
            dontTriggerObservers = false
        }
    }

丑陋但可行