Swift:将四个 Double 变量相乘时出错

Question

我在“AnalyzeInput”类的返回语句中不断收到错误消息，“无法使用类型为‘($T18, Double)’的参数列表调用‘*’”，这毫无意义，因为所有四个变量在其方法头中被定义为 Double。这是两个相关的类，删除了不相关的代码:

class AnalyzeInput {

     // Constructor, initialize InputInfo, add information to it etc etc

    var remainingToAnalyze: String
    var information: InputInfo

    func findOutput() {
        return information.getVolumeAmount() * information.getMeasurement().getMiliplier() * information.getConcentration() * information.getCompoundMolarMass()
    }
}

class InputInfo {
    var volumeAmount: Double = 0
    var measurementType: Measurement = Measurement(short: "null", singular: "null", plural: "null", multiplier: 0)
    var concentration: Double = 0
    var compoundMolarMass: Double = 0

    init () {
    }

    func setVolumeAmount(volumeAmount: Double) {
        self.volumeAmount = volumeAmount
    }

    func setMeasurementType(measurement: Measurement) {
        self.measurementType = measurement
    }

    func setConcentration(concentration: Double) {
        self.concentration = concentration
    }

    func setCompound(compoundMolarMass: Double) {
        self.compoundMolarMass = compoundMolarMass
    }

    func getVolumeAmount() -> Double {
        return volumeAmount
    }

    func getMeasurement() -> Measurement {
        return measurementType
    }

    func getConcentration() -> Double {
        return concentration
    }

    func getCompoundMolarMass() -> Double {
        return compoundMolarMass
    }
}

如何修复错误？

Answer 1

findOutput 的返回类型不是 Double。如果你想从它返回一个 double，你需要正确声明返回类型。此外，您不需要第二类中的所有这些 getter/setter 方法——您可以只使用点运算符来访问属性。最后，“multiplier”在您的回电中拼写错误。所以:

func findOutput() -> Double {
    return information.volumeAmount * information.measurement.multiplier * information.concentration * information.compoundMolarMass
}