在记录f＃中作为属性添加到地图

Question

I have this type:

type Model = {Ships: map<Mmsi, Ship>}
type Ship = {Latitude: float Longitude: float Speed: float Heading: float}

I am trying to figure out a way to add to the ship map through a message type

type msg = {Latitude: float Longitude: float Mmsi = int Time = string}

Using this function:

let update (msg : Msg) (currentModel : Model) : Model =
    // TODO: implement the new model based on the received message here
    let currentModel = 
        { 
            Ships = Map.Add(msg.Mmsi, msgToShip msg)
        }
    currentModel

However I am getting an error from the compiler as such: "Method or object constructor 'Add' is not static.

I am not especially experienced in f# or functional programming in general so any pointers to this would be most appreciated.

Answer 1

Capitalized Add is an instance method on the type Map<_, _> . Lowercase add is a function in the Map module. So what you wanted to call here was:

Ships = Map.add msg.Mmsi (msgToShip msg) currentModel.Ships

Or, also valid but less idiomatic:

Ships = currentModel.Ships.Add(msg.Mmsi, msgToShip msg)