计数对象数组中的错误

Question

我有这样的代码：

var activeCalculators = Calculators()

func numberOfCalculators()->Int{
        let activeCalculatorsArray = activeCalculators.calculators
        return activeCalculatorsArray!.count
    }


struct Calculators
{
    var calculators: [Calculator]?
    var activeCalculator: Int = -1
    var activeSummary: Bool = false
    var activeProfits: Bool = false

    public func getCalculators()-> [Calculator]
    {
        return calculators!
    }

    public mutating func setCalculators(calculators: [Calculator])
    {
        self.calculators = calculators
    }

    public func  getActiveCalculatorIndex()-> Int
    {
        return activeCalculator
    }

    public mutating func  setActiveCalculatorIndex( activeCalculator: Int)
    {
        self.activeCalculator = activeCalculator
    }

    public func  isActiveProfits()-> Bool
    {
        return activeProfits
    }

    public mutating func  setActiveProfits( activeProfits: Bool)
    {
        self.activeProfits = activeProfits
    }



    public func  isActiveSummary()-> Bool
    {
        return activeSummary
    }

    public mutating func setActiveSummary(activeSummary: Bool)
    {
        self.activeSummary = activeSummary
    }
}

override func viewDidLoad() {
print("XXXXXXXXXXXX: \(numberOfCalculators())")

}

当我运行我的函数: numberOfCalculators()时，我有错误:线程1:致命错误:意外地找到零，同时打开一个可选的值

我正试着把这个功能添加到我的课堂上：

public func countCalculators()->Int{
        return (calculators?.count)!
    }

但是他们我错了：

线程1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP，subcode=0x0)

你怎么能修好它？

Answer 1

首先，正确地展开它：

func numberOfCalculators()->Int{
    return activeCalculatorsArray?.count ?? 0
}

public func countCalculators()->Int {
    return calculators?.count ?? 0 // Suggested by Alexander
}

然后你需要set something before calling get。因此，在viewDidLoad中，不必先调用numberOfCalculators()，而是调用setCalculators()，这样计算器就有了一定的价值。

Answer 2

根据您提供的信息，在您阅读时，calculators似乎是零。您可能需要在您的getCalculators方法中进行一些检查.

guard let calcs = self.calculators else {
    print("No calculcators!")
    return [] // returns empty (no crash)
}

return calcs // return values

同时，最好能调查一下为什么你一开始就没有计算器。