{"id":21725,"date":"2018-06-07T14:58:50","date_gmt":"2018-06-07T18:58:50","guid":{"rendered":"https:\/\/mjtsai.com\/blog\/?p=21725"},"modified":"2018-09-03T15:17:06","modified_gmt":"2018-09-03T19:17:06","slug":"swift-4-2","status":"publish","type":"post","link":"https:\/\/mjtsai.com\/blog\/2018\/06\/07\/swift-4-2\/","title":{"rendered":"Swift 4.2"},"content":{"rendered":"

Ole Begemann<\/a>:<\/p>\n

\n

I made a “What’s new in Swift 4.2” playground<\/a> for Xcode 10: new collection algorithms, random numbers, enumerating enum cases, and more. <\/p>\n<\/blockquote>\n\n

Ole Begemann<\/a>:<\/p>\n

\n

Working with random numbers in Swift used to be a bit of pain because there was no native random number API. Developers had to fall back on C APIs provided by the operating system, which are often easy to misuse. Moreover, the preferred random number API differs between platforms (e.g. arc4random<\/code><\/a> vs. rand<\/code><\/a> vs. random<\/code><\/a>), making it difficult to write cross-platform code.<\/p>\n\n

Swift 4.2 makes this much easier by including a native and fairly full-featured random number API in the standard library. You can read about the full API and its design rationale in Swift Evolution proposal SE-0202<\/a>).<\/p>\n<\/blockquote>\n\n

Previously: Swift 4.1<\/a>.<\/p>\n\n

Update (2018-06-09): Roadfire Software<\/a> (via Hacker News<\/a>):<\/p>\n

In What’s New in Swift at WWDC 2018, Apple gave a quick overview of what’s new in Swift 4.2 and Swift 5. You can read my notes below, or you can watch the 40-minute video<\/a> and download the slides from Apple.<\/p><\/blockquote>\n\n

Ole Begemann<\/a>:<\/p>\n

\n

Problem: a manual CaseIterable implementation risks becoming incorrect as a type evolves. The compiler doesn’t catch this.<\/p>\n

Solution: a dummy function whose only purpose is to produce a compile error on (almost) the correct line when a new case is added.<\/p>\n

It’s ugly but it works.<\/p>\n<\/blockquote>\n\n

Update (2018-06-12): Ole Begemann<\/a>:<\/p>\n

\n

New in Swift 4.2, the compiler can generate a collection of an enum’s cases, relieving you from the error-prone task of maintaining such a list yourself. The Swift Evolution proposal that introduced this feature is SE-0194<\/a>.<\/p>\n

[…]<\/p>\n

The manual implementation is easy enough to write, but it has a major downside compared to compiler-generated code: we now have to remember to keep it up to date. If we later add another workout type to our enum, the compiler won’t alert us that our allCases<\/code> implementation is no longer correct. It will just silently return the wrong result.<\/p>\n\n

The only workaround I can think of is a little ugly, but it solves this problem in a really interesting way.<\/p>\n<\/blockquote>\n\n

Update (2018-08-14): Mattt Thompson<\/a>:<\/p>\n

Swift 4.2 refines Hashable<\/code> even further by introducing the Hasher<\/code> type and adopting a new universal hashing function.<\/p><\/blockquote>\n\n

Update (2018-09-03): Brent Simmons<\/a>:<\/p>\n

\n

The point still stands, though, that automatic hashing in the case of objects with lots of properties might be a performance hit. As always — use the profiler.<\/p>\n<\/blockquote>","protected":false},"excerpt":{"rendered":"

Ole Begemann: I made a “What’s new in Swift 4.2” playground for Xcode 10: new collection algorithms, random numbers, enumerating enum cases, and more. Ole Begemann: Working with random numbers in Swift used to be a bit of pain because there was no native random number API. Developers had to fall back on C APIs […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"apple_news_api_created_at":"2018-06-12T18:33:43Z","apple_news_api_id":"c9dcb48d-5f38-42e0-9115-6d7fa2635ab7","apple_news_api_modified_at":"2018-09-03T19:17:11Z","apple_news_api_revision":"AAAAAAAAAAAAAAAAAAAAAw==","apple_news_api_share_url":"https:\/\/apple.news\/Aydy0jV84QuCRFW1_omNatw","apple_news_coverimage":0,"apple_news_coverimage_caption":"","apple_news_is_hidden":false,"apple_news_is_paid":false,"apple_news_is_preview":false,"apple_news_is_sponsored":false,"apple_news_maturity_rating":"","apple_news_metadata":"\"\"","apple_news_pullquote":"","apple_news_pullquote_position":"","apple_news_slug":"","apple_news_sections":"\"\"","apple_news_suppress_video_url":false,"apple_news_use_image_component":false,"footnotes":""},"categories":[],"tags":[46,71,813,901],"class_list":["post-21725","post","type-post","status-publish","format-standard","hentry","tag-languagedesign","tag-programming","tag-random-numbers","tag-swift-programming-language"],"apple_news_notices":[],"_links":{"self":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts\/21725","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/comments?post=21725"}],"version-history":[{"count":5,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts\/21725\/revisions"}],"predecessor-version":[{"id":22601,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/posts\/21725\/revisions\/22601"}],"wp:attachment":[{"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/media?parent=21725"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/categories?post=21725"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mjtsai.com\/blog\/wp-json\/wp\/v2\/tags?post=21725"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}