Nested Types about swift-style-guide HOT 8 CLOSED

I haven't looked into it in detail but AFAICT, you already get an automatic namespace that is named after your project or framework. Nesting types just for the purpose of creating another namespace seems a little extreme.

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I like nested types for namespaces, but I think nested types in general are going to take some experimentation.

IIRC, JavaScript does a lot of nested nonsense in order to face private access, like returning functions that capture variables from other functions to hide their scope. It's a powerful feature, but it still feels kludgy to me when used for such purposes.

I'm hoping we have a better solution for the private thing from Apple (which everyone says we will) and then we see how that ties into this.
--------- Original Message --------- Subject: [swift-style-guide] Nested Types (#12)
From: "Ryan Nystrom" [email protected]
Date: 6/10/14 1:22 pm
To: "raywenderlich/swift-style-guide" [email protected]

Definitely a new feature for us. What are some do's/dont's that we should consider?
I really like the example used in "the book".
struct BlackjackCard { enum Suit: Character { // ... } enum Rank: Int { // ... } let rank: Rank, suit: Suit var description: String { // ... } } I love the idea of using nested "private" types to create container classes. Could we use nested types as a means to namespace library/framework classes?

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@hollance Oh very cool, I hadn't seen this.

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Yeah, I wasn't sure about how it works, either. For example:

min is an existing function

If x and y are Ints,

var min = min(x, y)

won't compile because it thinks you are using the name of the variable in its own declaration. So I figured if the compiler is too dumb to tell what's going on here, then I wasn't sure about things like making our own types.

But if we don't need to nest things to get the behavior we want, then we shouldn't. Nesting should be used for things where it solves a problem more easily than another solution.

--------- Original Message --------- Subject: Re: [swift-style-guide] Nested Types (#12)
From: "Ryan Nystrom" [email protected]
Date: 6/10/14 1:29 pm
To: "raywenderlich/swift-style-guide" [email protected]
Cc: "elephantronic" [email protected]

@hollance Oh very cool, I hadn't seen this.

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I just submitted the var min = min(x, y) thing as a bug report. It also happens with your own functions:

func hello() -> Int { return 100 }
var hello = hello()

I don't think this is related to nesting or namespaces in any way.

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Personally I think the example from the 'book' is a terrible one! The concept of a Suit is quite separate from the game of Blackjack, and one that you might want to use in a number of other contexts.

I personally use nested classes (in Java & C#) quite sparingly, I only use them when I am required to create a type purely to support the internal implementation of another type. And in this instance I make the nested type private (again I am assuming we will be able to do this in the future with Swift!)

Microsoft has some good guidance on the subject here: http://msdn.microsoft.com/en-us/library/vstudio/ms229027(v=vs.100).aspx

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That's how I've used nested types in Java too, @ColinEberhardt, almost entirely for implementation/parent-class specific reasons (holders and the like).

I could see the value w/ namespacing though, if you were to use some generic name for a class that "assisted" the parent class? Like Person has a PersonNameFormatter but you could just call it Person.NameFormatter? Thoughts?

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Has anyone used nested types yet? There is some interesting usage by Apple in the Lister WatchKit sample. But I'll close this with the feeling it's a little too uncommon right now to mention in our style guide, but please file an issue or pull request if you feel strongly otherwise.

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