<div dir="ltr">Some of this currently is being hacked into the language via the use of structs.</div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Dec 11, 2015 at 10:39 AM, T.J. Usiyan via swift-evolution <span dir="ltr"><<a href="mailto:swift-evolution@swift.org" target="_blank">swift-evolution@swift.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Namespaces</div><div>Author(s): TJ Usiyan</div><div><br></div><div>Introduction</div><div><br></div><div>A `namespace` keyword for swift hold related global variables.</div><div><br></div><div>Motivation</div><div><br></div><div>We often want to collect related variables which do not, for whatever reason, fit neatly into a type provided by Swift. Importing Objective C 'magic strings' as Joshua Sullivan does [here] is one such example. The solution he arrives at is a `struct` type with many type variables and no fields.</div><div><span style="white-space:pre-wrap"> </span></div><div><span style="white-space:pre-wrap"> </span>struct NotificationNames {</div><div><span style="white-space:pre-wrap"> </span> static let userDataChanged = "UserDataChangedNotificationName"</div><div><span style="white-space:pre-wrap"> </span> static let receivedAlert = "ReceivedAlertNotificationName"</div><div><span style="white-space:pre-wrap"> </span> static let peanutButterJellyTime = "ItsPeanutButterJellyTimeNotificationName"</div><div><span style="white-space:pre-wrap"> </span>}</div><div><br></div><div>Users of this API are not meant to create instances of this type, yet it is still possible. A solution to this is to use an `enum` without cases. </div><div><br></div><div><span style="white-space:pre-wrap"> </span>enum NotificationNames {</div><div><span style="white-space:pre-wrap"> </span> static let userDataChanged = "UserDataChangedNotificationName"</div><div><span style="white-space:pre-wrap"> </span> static let receivedAlert = "ReceivedAlertNotificationName"</div><div><span style="white-space:pre-wrap"> </span> static let peanutButterJellyTime = "ItsPeanutButterJellyTimeNotificationName"</div><div><span style="white-space:pre-wrap"> </span>}</div><div><br></div><div>No instances of the `enum` can be made. That this inability to create an instance is intentional is only conveyed via the type system. </div><div><br></div><div>Proposed solution</div><div><br></div><div>Clarity would be greatly improved if we could use `namespace` as a synonym for an enum with no cases. This would allow us to avoid repetition of `static` as well.</div><div><br></div><div><span style="white-space:pre-wrap"> </span>namespace NotificationNames {</div><div><span style="white-space:pre-wrap"> </span> let userDataChanged = "UserDataChangedNotificationName"</div><div><span style="white-space:pre-wrap"> </span> let receivedAlert = "ReceivedAlertNotificationName"</div><div><span style="white-space:pre-wrap"> </span> let peanutButterJellyTime = "ItsPeanutButterJellyTimeNotificationName"</div><div><span style="white-space:pre-wrap"> </span>}</div><div><br></div><div>Detailed design</div><div><br></div><div>Namespaces can be represented in the type system as enums. All variables declared in a namespace's scope would be type variables.</div><div><br></div><div>Impact on existing code</div><div><br></div><div>This is an additive change and, as such, should not break any existing code. Though it doesn't matter, this addition could possibly attain ABI compatibility if namespaces are represented as enums without cases.</div><div><br></div><div>Alternatives considered</div><div><br></div><div>Don't implement namespaces. Developers could continue(begin?) using an empty enum to hold type variables.</div></div>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div><span style="font-size:16px;line-height:19.2px"></span><span style="font-size:12.8px"> Wizard</span><br></div><div><a href="mailto:james@supmenow.com" target="_blank">james@supmenow.com</a></div><div>+44 7523 279 698</div></div></div></div></div></div>
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