[swift-users] Class vs Structures

Taylor Swift kelvin13ma at gmail.com
Fri Jun 30 01:39:19 CDT 2017

```The Ray Wenderlich style guide contains *some* useful insights, but you
should not take it as a “swift best practices” guide, or even a good code
style guide for your own projects. At the risk of sounding blunt, the RW
style guide is optimized for blog posts and cheap tutorials, not a cohesive
Swift code base you have to maintain over time. In addition that website is
heavily iOS-developer oriented, and the iOS platform forces you to interact
with a lot of Objective C frameworks which are more reference-oriented than
native Swift code should be.

Enum scoping is when you want to group free floating functions into a
common namespace to avoid polluting the global scope. For example one of
the libraries I maintain has a collection of internal math functions which
are handy to have around.

enum Math
{
typealias IntV2    = (a:Int, b:Int)
typealias IntV3    = (a:Int, b:Int, c:Int)
typealias DoubleV2 = (x:Double, y:Double)
typealias DoubleV3 = (x:Double, y:Double, z:Double)

@inline(__always)
private static
func fraction(_ x:Double) -> (Int, Double)
{
let integer:Int = x > 0 ? Int(x) : Int(x) - 1
return (integer, x - Double(integer))
}

@inline(__always)
static
func fraction(_ v:DoubleV2) -> (IntV2, DoubleV2)
{
let (i1, f1):(Int, Double) = Math.fraction(v.0),
(i2, f2):(Int, Double) = Math.fraction(v.1)
return ((i1, i2), (f1, f2))
}

@inline(__always)
static
func fraction(_ v:DoubleV3) -> (IntV3, DoubleV3)
{
let (i1, f1):(Int, Double) = Math.fraction(v.0),
(i2, f2):(Int, Double) = Math.fraction(v.1),
(i3, f3):(Int, Double) = Math.fraction(v.2)
return ((i1, i2, i3), (f1, f2, f3))
}

@inline(__always)
static
func add(_ v1:IntV2, _ v2:IntV2) -> IntV2
{
return (v1.a + v2.a, v1.b + v2.b)
}

...
}

Some, but not all projects will end up with a `Constants`, enum to store
global constants too. Beyond that, you shouldn’t be Enum scoping a lot, it
usually isn’t hard to find a real type where some method or constant
belongs. That being said, you can find a few examples of this pattern in
the Swift standard library: `Unicode`, `CommandLine` and `MemoryLayout`
come to mind.

On Fri, Jun 30, 2017 at 12:12 AM, Vitor Navarro via swift-users <
swift-users at swift.org> wrote:

> Hi Alex,
>
> Thank you for the reply, actually Taylor gave me a great answer which
> solved my question, that was "struct or classes and when should we apply
> each".
>
> Regarding the reference I found this https://github.com/
> raywenderlich/swift-style-guide#code-organization which doesn't follow
> exactly the structs most of the times approach or the protocol driven
> development (WWDC)
>
> Again thanks.
>
> 2017-06-29 14:21 GMT-04:00 Alex Blewitt <alblue at apple.com>:
>
>> On 29 Jun 2017, at 18:16, Vitor Navarro via swift-users <
>> swift-users at swift.org> wrote:
>>
>> Hi,
>>
>> I know this question is probably done a thousand times, but I wanted to
>> hear from Swift dev community.
>>
>>
>> What is the question?
>>
>> I think both of them have right places for usage depending on the
>> occasion but documentation, WWDC and the internet give opposite answers
>> regarding this.
>>
>>
>> Do you have references that you can share?
>>
>> Do you guys have any guideline regarding usage here?
>>
>>
>> The Swift Programming Language  sums up the similarities and differences
>> between classes and structures quite well:
>>
>> https://developer.apple.com/library/content/documentation/Sw
>> ift/Conceptual/Swift_Programming_Language/ClassesAndStructures.html
>>
>> Alex
>>
>>
>
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users
>
>
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```