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.send { color:#77bb77; }
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.error { color:#AA0000; }</style></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div class="bloop_markdown"><p>There are still a lot of open questions here to solve.</p>
<ul>
<li>How to statically guarantee the uniqueness + immutability of the <code>hashValue</code>s?
<ul>
<li><p>Should we allow only the usage of an initializer?</p></li>
<li><p>Sometimes an init might be not enough and you’d wish you can use custom function which would return the same value for the same input you provide.</p>
<pre><code class="swift">struct A : Hashable { … }
enum B : A {
case a: A(someLabel: someInput)
case b: createAFunction()
case c: createA(with: someOtherInput)
}
</code></pre></li>
<li><p>Should we allow only value types here or how do we handle reference types?</p></li>
</ul></li>
</ul>
<p>A protocol to create custom enum-like types would be really interesting and useful. Instead of <code>switch</code> checking the value that conforms to that new protocol directly I’d suggest that we need some kind of an interface to satisfy and enable the enum-like <code>switch</code> usage (or maybe I’m totally wrong here).</p>
<pre><code class="swift">protocol SomeFancyName : RawRepresentable {
var interface: SomeType { get }
}
struct C : SomeFancyName { /* implement */ }
let c = C.someCase
switch c.interface {
case .someCase:
// Handle
case .someOtherCase:
// Handle
// No need for `default` when all cases are present
}
</code></pre>
<p>I couldn’t think up a simple and elegant model for such a protocol. Any suggestions is welcome.</p>
<ul>
<li><p>Does the core team and the community feel this might have some potential future?</p></li>
<li><p>Does this impact the ABI somehow?</p></li>
</ul>
<p></p></div><div class="bloop_original_html"><style>body{font-family:Helvetica,Arial;font-size:13px}</style><div id="bloop_customfont" style="font-family:Helvetica,Arial;font-size:13px; color: rgba(0,0,0,1.0); margin: 0px; line-height: auto;"><br></div> <br> <div id="bloop_sign_1475563657807241984" class="bloop_sign"><div style="font-family:helvetica,arial;font-size:13px">-- <br>Adrian Zubarev<br>Sent with Airmail</div></div> <br><p class="airmail_on">Am 4. Oktober 2016 um 08:25:24, Rien (<a href="mailto:rien@balancingrock.nl">rien@balancingrock.nl</a>) schrieb:</p> <blockquote type="cite" class="clean_bq"><span><div><div></div><div>+1.
<br>
<br>I have several cases where I cannot use enums, this proposal would solve that.
<br>
<br>
<br>> On 03 Oct 2016, at 21:53, Adrian Zubarev via swift-evolution <swift-evolution@swift.org> wrote:
<br>>
<br>> I made a typo in my previous post.
<br>>
<br>> Bikeshdding with correct types:
<br>>
<br>> struct A : Hashable { /* implement everything */ }
<br>>
<br>> // Variant 1:
<br>> enum Test : A {
<br>> case something = A(value: "something")
<br>> case nothing = A(value: "nothing")
<br>> }
<br>>
<br>> // Variant 2:
<br>>
<br>> protocol SomeFancyName : RawRepresentable { … }
<br>>
<br>> struct Test : SomeFancyName {
<br>>
<br>> let rawValue: A
<br>> init?(rawValue: A) {
<br>> // Implement + reject unwanted `A`s
<br>> }
<br>>
<br>> static let something = Test(rawValue: A(value: "something"))
<br>> static let nothing = Test(rawValue: A(value: "nothing"))
<br>> }
<br>>
<br>> let value = Test.something
<br>>
<br>> switch value {
<br>>
<br>> case .something:
<br>> // handle
<br>>
<br>> case .nothing:
<br>> // handle
<br>>
<br>> // Because of `SomeFancyName` the switch can use enum-like pattern matching + does not need the `default` case when all cases are present
<br>> }
<br>>
<br>>
<br>>
<br>>
<br>> --
<br>> Adrian Zubarev
<br>> Sent with Airmail
<br>>
<br>> Am 3. Oktober 2016 um 21:50:07, Adrian Zubarev (adrian.zubarev@devandartist.com) schrieb:
<br>>
<br>>> Hi there,
<br>>>
<br>>> I’m interested if this idea has some potential future in Swift or not.
<br>>>
<br>>> Currently RawRepresentable enums accept only a subset of literal types like String, Character and the Integer family (enum Name : String { … }).
<br>>>
<br>>> Sometimes this is not enough for my use-case and I wish I could feed my enums with other Hashable types!
<br>>>
<br>>> As a workaround I can create a custom struct or even a class and conform it to RawRepresentable and fake an enum with some static variables (similar to what is done with OptionSet types).
<br>>>
<br>>> The problem there is that I cannot use the same switch pattern matching like with enums. I’d wish either enums could accept Hashable types (maybe with some restriction) or the existence on a protocol to build custom enum-like types with strucs/classes and use the same switch pattern matching.
<br>>>
<br>>> struct A : Hashable { /* implement everything */ }
<br>>>
<br>>> // Variant 1:
<br>>> enum Test : A {
<br>>> case something = A(rawValue: A(value: "something"))
<br>>> case nothing = A(rawValue: A(value: "nothing"))
<br>>> }
<br>>>
<br>>> // Variant 2:
<br>>>
<br>>> protocol SomeFancyName : RawRepresentable { … }
<br>>>
<br>>> struct Test : SomeFancyName {
<br>>>
<br>>> let rawValue: A
<br>>> init?(rawValue: A) {
<br>>> // Implement + reject unwanted `A`s
<br>>> }
<br>>>
<br>>> static let something = A(rawValue: A(value: "something"))
<br>>> static let nothing = A(rawValue: A(value: "nothing"))
<br>>> }
<br>>>
<br>>> let value = Test.something
<br>>>
<br>>> switch value {
<br>>>
<br>>> case .something:
<br>>> // handle
<br>>>
<br>>> case .nothing:
<br>>> // handle
<br>>>
<br>>> // Because of `SomeFancyName` the switch can use enum-like pattern matching + does not need the `default` case when all cases are present
<br>>> }
<br>>>
<br>>>
<br>>>
<br>>> --
<br>>> Adrian Zubarev
<br>>> Sent with Airmail
<br>>
<br>> _______________________________________________
<br>> swift-evolution mailing list
<br>> swift-evolution@swift.org
<br>> https://lists.swift.org/mailman/listinfo/swift-evolution
<br>
<br></div></div></span></blockquote></div><div class="bloop_markdown"><p></p></div></body></html>