CODEWITHSUNDEEP
f#f#-interactive
ingted
ingted

Reputation: 45

F# static member changes each time when accessed

Here is a very simple class with static property:

[<AbstractClass; Sealed>]
type test () = 
    static member ttc = (new Random()).Next()

When I access ttc, it always changes... like this: (in fsi.exe)

it changes...

What is my purpose is to store values in static member:

type typDimTablesArray () = 
static member DimApplication        = typDimTables.DimApplication      |> Seq.toArray
static member DimApplicationState   = typDimTables.DimApplicationState |> Seq.toArray
static member DimDatetime           = typDimTables.DimDatetime         |> Seq.toArray
static member DimDbQuery            = typDimTables.DimDbQuery          |> Seq.toArray
static member DimDeveloper          = typDimTables.DimDeveloper        |> Seq.toArray
static member DimPlatform           = typDimTables.DimPlatform         |> Seq.toArray

But each time I access typDimTablesArray.DimDatetime.Length It just query the database again and never store the data in the static member...

Upvotes: 2

Views: 160

Answers (1)

s952163
s952163

Reputation: 6324

Here's a short example of the differences:

type Test3() =
    let random = new System.Random()
    let y = random.Next()
    member __.X = random.Next()
    member __.Y = y
    static member val Z = (new Random()).Next()

let x = Test3()

x.X 
x.X
x.Y
x.Y
Test3.Z
Test3.Z

Also, you could just create an instance of your type and pass in whatever object you need to work on. Now if it's something lazy you might need to cache it: 

let rnd = new System.Random()
let rnds = Seq.init 10 (fun _ -> rnd.Next())

type Test4(rndsX:int seq) =
    let xx = rndsX |> Seq.cache
    member __.Length = xx |> Seq.toArray |> Seq.length
    member __.First = xx |> Seq.head
    member __.Last = xx |> Seq.last

Upvotes: 3

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