它没有方法 the_method

Question

假设liste是某个对象列表。

let rec sum liste any_method = match liste with
    | [] -> 0
    | obj::r -> obj#any_methode + sum r any_method

如果我使用 sum my_list_of_objects the_method，我会得到 This expression has type int list. It has no method the_method。

是否有解决该问题的方法？

更新这是一个简单的案例

 class point = 
    object
      val mutable x = 1
      method getx = x
      method move d = (x <- x + d)
  end;;

假设liste_points对象列表point。

let func liste methode = map (fun obj -> obj#methode 5) liste;;
func liste_points move;;

上面的小代码出现了下面的错误:

Error: This expression has type point list
       but an expression was expected of type
         (< methode : int -> 'b; .. > as 'a) list
       Type point = < getx : int; move : int -> unit >
       is not compatible with type < methode : int -> 'b; .. > as 'a 
       The first object type has no method methode

我怎样才能完成这项工作？

Answer 1

新答案

这里有一个 class 实例包含两个不同的整数：

class intx2 = object
    val mutable a : int = 0
    val mutable b : int = 0
    method set_a v = a <- v
    method get_a = a
    method set_b v = b <- v
    method get_b = b
end

let get_a_fn obj = obj#get_a
let get_b_fn obj = obj#get_b

let rec sum getter = function
    | [] -> 0
    | obj :: rest -> getter obj + sum getter rest

您可以像这样总结此类对象列表的 a 值：

sum get_a_fn list_of_objs

您可以这样总结 b 个值：

sum get_b_fn list_of_objs

它没有方法 the_method

It has no method the_method

methods

ocaml

object