f# - 需要帮助将带有泛型的接口(interface)从 C# 转换为 F#

Question

我有这个 C# 代码

public interface IDinnerRepository : IRepository<Dinner>
{
    IQueryable<Dinner> FindByLocation(float latitude, float longitude);
    IQueryable<Dinner> FindUpcomingDinners();
    IQueryable<Dinner> FindDinnersByText(string q);
    void DeleteRsvp(RSVP rsvp);
}

和

public interface IRepository<T>
{
    IQueryable<T> All { get; }
    IQueryable<T> AllIncluding(params Expression<Func<T, object>>[] includeProperties);
    T Find(int id);
    void InsertOrUpdate(T dinner);
    void Delete(int id);
    void SubmitChanges();
}

我想将其翻译成 F#。如何制作泛型接口(interface)？ F# 接口(interface)的 MSDN 示例实际上并没有等效项。据我所知。

Answer 1

实际上有两种定义通用接口(interface)的方法，但几乎所有 F# 代码都使用您在现有答案中提到的样式。另一个选项仅用于某些标准 F# 类型，例如 'T option 和 'T list:

type IRepository<'T> = // The standard way of doing things
type 'T IRepository =  // Used rarely for some standard F# types

至于你的示例接口(interface)中出现的其他成员类型，其中一些其实有点意思，所以这里有一个比较完整的翻译(仅供以后引用!)

// We inherit from this type later, so I moved it to an earlier location in the file
type IRepository<'T> =
  // Read-only properties are easier to define in F#
  abstract All : IQueryable<'T>
  // Annotating parameter with the 'params' attribute and also specifying param name
  abstract AllIncluding 
    : [<ParamArray>] includeProperties:Expression<Func<'T, obj>>[] -> IQueryable<'T>


type IDinnerRepository =
  // Inherit from another interface
  inherit IRepository<Dinner>

  // And add a bunch of other members (here I did not specify parameter names)
  abstract FindUpcomingDinners : unit -> IQueryable<Dinner>
  abstract FindDinnersByText : string -> IQueryable<Dinner>