C# object initialization syntax in F#

Question

Please note: this question is not the same as this question.

I recently came across some C# syntax I hadn\'t previously encountered:

Is there any wa

Answer 1

F# 4.0 came out with a feature which might be useful to encapsulate @plinth's answer. It allows the creation of extension properties, which can be initialized in the constructor.

Answer 2

Would it make sense to encapsulate the construction into a separate initializer function?

let layerInit layer radius color offset opacity =
    do
       layer.ShadowRadius <- radius
       layer.ShadowColor <- color
       layer.ShadowOffset <- offset
       layer.ShadowOpacity <- opacity
    layer // I do this in case you want to use this fluently or pass in new Layer()

Then use that in your code:

let nameLabel = new UILabel ( TextColor = UIColor.White )
layerInit nameLabel.Layer 3.0f UIColor.Black.CGColor new System.Drawing.SizeF(0.0f,1.0f) 0.5f |> ignore

Answer 3

I don't think F# allows setting nested properties during initialization. A workaround, assuming you're the author of the API, is to pass the entire object to the constructor. This eliminates the need for getter and setter with different accessibilities and makes for much cleaner F# code overall.

type Two() =
    member val Test = "" with get, set

type One(twoProperty) =
    member val TwoProperty = twoProperty

let test = One(Two(Test="foo"))

As you mentioned in your comment, you could create a helper function accepting various properties as optional parameters. A type extension would work well for this:

type UILayer with
    member this.Configure(?shadowRadius, ?shadowColor, ?shadowOffset, ?shadowOpacity) = 
        this.ShadowRadius <- defaultArg shadowRadius this.ShadowRadius
        this.ShadowColor <- defaultArg shadowColor this.ShadowColor
        this.ShadowOffset <- defaultArg shadowOffset this.ShadowOffset
        this.ShadowOpacity <- defaultArg shadowOpacity this.ShadowOpacity

let nameLabel = UILabel(TextColor=UIColor.White)
nameLabel.Layer.Configure(
    shadowRadius=3.0f, 
    shadowColor=UIColor.Black.CGColor, 
    shadowOffset=SizeF(0.0f, 1.0f), 
    shadowOpacity=0.5f)