汽车租赁商业模式

Question

我是 F# 新手，所以请怜悯。尝试使用 F# 为汽车租赁业务建模。我的类型是：

• 客户
• 司机
• 汽车
• 车辆类型
• 租赁协议尚未实施

我的具体问题是 F# 类可以有受歧视联盟的成员吗？汽车应该有一个属性来反映它是什么类型的车辆...紧凑型、轿车、卡车等...下面是我到目前为止的代码...

namespace DSL2

// a DU
type vehicleType =  Truck | Compact | Econ | Sedan

// a record
type Customer =  {firstName: string; lastName: string; gender: string}

//a class implicit ctor'tion
type Car(numdoors:int ,  make: string , year:int)  = class
    member this.NumDoors = numdoors
    member this.Make = make
    member this.Year = year  
end

//a class explicit ctor'tion
type Car2 = class
    val NumDoors: int
    val Make: string
    val Year: int

    (*first ctor*)
    new (numDoors, make, year) = 
        {NumDoors = numDoors; Make = make; Year = year}
        
 end

Answer 1

是的，可区分联合就像任何其他类型一样，可以用作任何字段、属性、构造函数参数等的类型。

只需将

vehicleType

类型的参数添加到

Car

构造函数即可：

type Car(numdoors:int, make: string, year:int, vehicleType : vehicleType) = class
    member this.NumDoors = numdoors
    member this.Make = make
    member this.Year = year
    member this.VehicleType = vehicleType
end

请注意，使用首字母小写字母命名类型是不好的 F# 风格，因此我建议将其重命名为

VehicleType

。

Answer 2

是的，只需将成员添加到类中并将其包含在具有所需值的构造函数中即可。

// a DU
type vehicleType =  Truck | Compact | Econ | Sedan

// a record
type Customer =  {firstName: string; lastName: string; gender: string}

//a class implicit ctor'tion
type Car(numdoors:int ,  make: string , year:int)  = class
    member this.NumDoors = numdoors
    member this.Make = make
    member this.Year = year  
end

//a class explicit ctor'tion
type Car2 = class
    val NumDoors: int
    val Make: string
    val Year: int
    val DU: vehicleType

    (*first ctor*)
    new (numDoors, make, year, cust) = 
        {NumDoors = numDoors; Make = make; Year = year;  DU = Truck }
 end