swift api design guidelines ◂ Voltar
And good API design helps us write code that is clear, concise and beautiful in Swift. explicitly. So that's a lot about Swift. You can notice there's a whole lot of .swift files on the left. Now, we could try adding a typedef to try, So, how will this API look if we were going, Well, we'd probably make a new wrapper type around string. to enable the smallest possible code with the fewest characters. Also, in Swift 3 NSCalendar, it's now just known as Calendar. Notice how that reads well. in the mind that what we're looking for is terse code. and how they work is there in the contextual information. And yes, I know this bug is shallow and a developer would catch it right away. with your libraries and your APIs nicely. these names make documentation read naturally: These, however, make the documentation awkward and ungrammatical: Take advantage of defaulted parameters when it simplifies common So, we have method names and we have types. that this should really just be an initializer. All right? These names have widely precedented term such as sin(x) is preferable to an Pretty much all the code that you've written. understand all of them, and occasional surprising relationships—for To facilitate use as a quick reference, the details of many guidelines 0 reviews for API Design Guidelines in Swift 3 online course. And now notice what the call site looks like here. And you can see Swift rendering an opinion. Swift code is compact compared to Objective-c, but that is not a goal in API Design. Copyright © 2021 Apple Inc. All rights reserved. when you have extra information in there that you don't need. We're going to talk about the philosophy behind these guidelines. You'll see these proposal numbers throughout the talk. e.g. We can append a path component to it. And in this bunch of code we actually have verbosity that's. I talked a little bit about the scale of the Grand Renaming. But in Swift 3 we support full compound naming. Clarity is more important than brevity . And we will be focusing on the Swift use site, So we add NS Swift Name and we use typename.membername in order, to tell the Swift compiler that kCGColorWhite should be imported, And of course, the Swift use site can now use the properly. So, let's revisit the code from before. So this is removing specifically some element. two when those arguments are not central to the call’s meaning: Begin names of factory methods with “make”, (e.g. So, we have method names and we have types. I would just say, remove(ted). /// is generated by the expression `String(x)`. But, clear code has to hit the correct point in this sort of spectrum of terseness to verbosity. And so between #selector and #keyPath, you can essentially not worry about the Objective-C names. It's really the APIs you use day in and day out. value preserving type conversion. It is better to name a contiguous data structure Array than to I need to put an argument label in there. when you do care about the Objective-C names. The first argument label breaks it up so that it reads well and it's clear that what we're dismissing is the actual view controller. as part of the API Design Guidelines document. Organic compounds, append to it. Maybe ask your Swift compiler friends on Twitter or something. I talked a little bit about the scale of the Grand Renaming. To restore clarity, precede each weakly typed parameter with a And if you need reassurance about what a particular type is, if it'd help your understanding, of course, the answer is just an option click away inside Xcode. You just pass in the argument label setter or getter. /// Returns `true` iff `other` is entirely within the area of `self`. And these APIs were designed based on the coding guidelines for Cocoa. Clarity is more important than brevity. But for now, let's talk about the guidelines themselves. Also, in Swift 3 NSCalendar, it's now just known as Calendar. Now, then we're going to talk about the Grand Renaming. with no argument label here to append a character. Imported Objective-C APIs. However, when Element Name functions and methods according to their side-effects. Don’t say “epidermis” if “skin” will serve your purpose. the term strictly in accordance with its accepted meaning. their roles, rather than their type constraints. In such cases, begin the argument label after the preposition, to argument labels means the first argument will Depending on the API product you are trying to access, you will be using one of the two types of OAuth, Password Grant Type or JWT Bearer Token Grant Type.Check the securitySchemes defined in the … Streaming is available in most browsers, and in the WWDC app. And the importer will create you the new type around this. And any global variables of this type will get imported. It's wrong. And then refer to an Objective-C property. We'll take this little API here that adds a child view at some particular point within some main view. We're going to start by calling it removeItem. This guideline will be added to the "Parameters" section of the Swift API Design Guidelines: If your API will run in production, prefer #fileID over alternatives. when you're implementing optional protocol methods. Okay. It's a lot of change. for just don't feel right when they're in Objective-C. So in Swift 3 we introduced a new attribute just, through NS Extensible String Enum when you wish. Terms of art are an essential communication tool, but should only be Verbosity hurts readability. Good API design is always focused on the use site. So here we might say, okay, we have the friends collection. factory methods calls or a fundamental type such Int or String, type information and Protocols that describe what something is should read as nouns (e.g. How can we make it feel Swifty? Abbreviations, especially non-standard Document the complexity of any computed property that is not You take a look at Swift code, and it's instantly recognizable. So, in Swift, a function name is comprised of so-called base name, which here is remove in both of these APIs, as well as all of the argument labels for the arguments. So I'm going to start with what you get for free automatically. In practice, this guideline along with those for Clarity at the point of use is your most important goal. So, when you name a method, name it based on its side effects. It is absolutely true that someone can go and use names like A and B and C for all the variables. And that implementation detail is leaking out. Apple is leading by example. So we ask for X reversed. Now, with Objective-C, the APIs were already object-oriented. ones, are effectively terms-of-art, because understanding depends on But the fact that a user of this API has to remember what it is and it's not a valid string to use here, that's an unnecessary cognitive burden. So it's a much nicer development experience. takes a transform and rotates it about a given offset. And now there's one conceptual API of just removing an item from a collection has different names throughout the source base. element equal to x, rather than using x to indicate the ambiguities in overload sets. Yes! Because this is a really, really weak link between this string literal, which is super easy to mistype, and the method above that you actually meant to call. Now, selectors aren't the only sort of stringly type thing we have when talking about Objective-C method names. to make a new wrapper type around your string. The entire Swift standard library is being reviewed and updated to follow the Swift API design guidelines. But the clarity is the most important aspect. otherwise be ambiguous or unclear. For example, if you're wiring up target action. You can also use NS Swift Name in order to nest types. e.g., print(x), x.sort(), x.append(y). But now, our users can use the computed property directly. Clarity is more important than brevity. Anything that can be exposed to Objective-C from Swift, The Swift language itself abstracts away the need to worry, and yet it gives you the control you need for those times. While this is easy to do for protocols that are stand-alone (SequenceType becomes Sequence), I’m not sure how to update my APIs in which a protocol provides the base for an implementation. These methods form a semantic family, and the argument types So I'm going to put up a bunch of code here. As you're reading this call in context, you know what that local variable is. of this extra rich contextual information. And when you're in that context, you have all of this extra rich contextual information. You just write everything in terms of the Swift names and you stay in that set of names. Those with side-effects should read as imperative verb phrases, Thank you to David James for spotting this! but fundamentally it's driven by heuristics. So slightly different APIs have different names. period. Reverse it. Here we have two methods; saveToURL, forSaveOperation and revertToContentsOfURL. Modern Swift API Design - WWDC 2019 - Videos - Apple Developer That is, when the compiler sees myArtist.Name it maps it. Because we have experience from a much larger community. Various minor points * Will these guidelines … You can also use NS Swift Name in order to nest types. preposition, Give me the document directory appending this particular, So these rules, and many, many more, are described on Swift.org. And last, we looked at the new functionality, in the Swift compiler so that you can have your own, For more information, visit the page for this site, at developer.apple.com and check out Swift.org, the homepage, of the open source Swift project where you can see all, But Grand Central Dispatch has had its own Great Renaming using. /// Inserts `newElement` at `self.endIndex`. and understood by users. uses. Again, you can go look at Swift.org, look up this proposal number to see more information about that particular change to the Swift language. And so this is great when you're implementing a delegate. of the other crazy redundant stuff, they're now methods. great summary. That's CGAffineTransformMakeTranslation as well as CGAffineTransformMakeRotation on all of these. And so when you have one of these prepositional phrases, if you essentially can't form a grammatical phrase. It's just restating information that's already in the strong static type system that will be enforced by the Swift language. There's the word item that's part of our name. But I just want to look at how does this look? and the method above that you actually meant to call. This is actually a principle of the Swift language itself. Don’t surprise an expert: anyone already familiar with the term If we look at, say, the API that removed something in a particular position. e.g. So maybe the problem is that we should stop trying, to get these innocuous sort of general words in there, But moreover, if I do this, if I try to get really specific, And now there's one conceptual API of just removing an item, from a collection has different names throughout the, It's harder to recognize that actually we're talking. You don't have to care what that Objective-C name is. Remove person ted from the list of friends. Equatable, ProgressReporting). What's that even mean? CGColorCreateGenericRGB as well as all of the other many. Let me start with global variables to show you what I mean. And every now and then you want to specify your own name. For example: Default arguments are generally preferable to the use of method Collections in Swift use the term element. #keyPath does exactly what you'd expect. In all cases, this is a zero cost overhead. So my first API here removeBoxes (withLabel:WWDC). ⎟, /// - **Parameter terminator**: text to be printed ⎬ Parameters section, /// at the end. thing. And of course, the Swift use site can now use the properly nested property. parameter names do not appear at a function or method’s point of But what if you're an Objective-C developer or are working with a mixed project? Remember earlier when we created a new calendar identifier type? Name Mutating/nonmutating method pairs consistently. The goal of your API is to fit in with the rest of the code so that the end result is beautiful. In particular, omit words that because we're probably using value types here anyway. There's a lot of change coming with Swift 3. It's a compound made up of elements. when it's being migrated from Swift 2 to Swift 3. O(1). Acronyms and initialisms It's harder to recognize that actually we're talking about the same thing in different contexts. And if two APIs that share the same compound name. Is child adding something? about the same thing in different contexts. Label tuple members and name closure parameters where they And because the type context is clearer, we can even just say .gregorian. of that delegate method you want to implement. And the importer will create you the new type around this. Swift 3 API Best Practices by Reda Lemeden @kaishin; What does it mean to be Swifty? We take a transform. have a profound impact on your design, so don’t put it off. There's the word item that's part of our name. And we see it in actual metrics when we talk about apps that have been ported into Swift and written in Swift. Avoid obscure termsif a more common word conveys meaning justas well. When evaluating a design, reading a declaration is seldom Contribute to Boxue/swift-api-design-guidelines development by creating an account on GitHub. And we have this string literal. appear at first to be sharply distinct. and produces the Objective-C name for that method. “ing” suffix to name its nonmutating counterpart. /// approximation of `valueToApproximate`. appear in your API. And these wonderful APIs we use. This is what we jokingly refer to as stringly-typed API. all the things you don't need because they're redundant. So I'm going to start with what you get for free automatically in the Swift 3 compiler. We don't need that extra variable result. Because what is your mind doing as you're reading through this verbose code? of a small Swift app called Lister we've been shipping. verticalPositionOnUnitCircleAtOriginOfEndOfRadiusWithAngle(x). Conversion in the other direction, however, That's fine. And so here we have reverse a collection. But their argument labels are different because they do different things. /// Returns `true` iff `self` contains an element equal to. You have uses of related APIs. part of a grammatical phrase, it should have a label. without calling any wrappers or intermediaries or overlays. correctly translating them into their non-abbreviated forms. Why, after two years of working with Swift are we changing all the APIs that you work with on a daily basis? You can get a sense of what the types are just, And indeed, in Swift you probably wouldn't write the code, You would probably align that type information. Protocol to the protocol name: Compensate for weak type information to clarify a parameter’s role. families, because they impose a lower cognitive burden on anyone The Swift API Design Guidelines is like an instruction manual for how to craft the “words” in your code: how you name variables, parameters, method names. Now, you can overload based on type information. the answer is just an option click away inside Xcode. So, we're going to talk through what that means for your code. And of course, the Swift use site, it just calls it like a method. Now, method names will get you a long way towards a Swifty API, but this doesn't quite go far enough. And of course -- hold your applause -- and of course CGContextAddPath, ContextPath and all of the other crazy redundant stuff, they're now methods. Why? Swift Standard Library. for a different language with a different character. It's just restating information that's already, in the strong static type system that will be enforced. And so now CGContextFillPath is now just the method fill path. Instead, strive to choose a name that expresses the However, there are times when you're interacting, with the system where you actually do need the. Basically every Swift file in the entire project is changed by the transition from Swift 2 to Swift 3. Now, inside that API we have a prepositional phrase. They're just overloaded on different types for convenience. from the compiler telling you that that doesn't make sense. Let's read this out remove at the position of former friend. This is also known as, "Oh, no! in that case do not form part of a grammatical phrase, so they given position within a collection. And of course, the compiler will validate that that property exists, that it's exposed to Objective-C and get the right Objective-C name for it. Avoid obscure terms if a more common word conveys meaning just It's in context. Please check your Internet connection and try again. is that Swift makes sure that that method exists. Does it skew toward safety, performance? This is not a use case. In the new Swift API design guidelines, the commonly-used Type suffix for protocols is being dropped. So maybe the problem here is really that the word item isn't sufficiently descriptive. We don't need a first argument label to make it read well, and so we leave it out. fundamental in modern computing, so every programmer knows—or And because the type context is clearer, we can even omit the type name. And good API design helps us write code that is clear, And that's every bit as true whether you're writing your API. People will look at that API in code, or maybe look at the documentation for it a couple of times. Because fundamentally these are the same operation. Bring APIs into adherence with the Swift API Design Guidelines in Swift Impacts a huge number of APIs • The Swift standard library • All Cocoa and Cocoa Touch frameworks • Core Graphics and Grand Central Dispatch get “Swifty” makeover SE-0005 SE-0006 SE-0086 SE-0088 That is, when the compiler sees myArtist.Name it maps it directly to the corresponding C function without calling any wrappers or intermediaries or overlays. updating an instance in-place. In “narrowing” type conversions, though, a label that describes /// Returns a copy of `self` with all the newlines stripped. should be named using the suffixes able, ible, or ing /// Returns the `n`th row in the given table. Highly recommend that you read them and try, they're not interesting unless they actually are, Which is the application of these guidelines, to the Swift Standard Library, to the Cocoa, and Cocoa Touch APIs as well as targeted improvements to APIs. No Prefixes in Swift-only Frameworks C and Objective-C symbols are global Swift’s module system allows disambiguation Remember — each source file brings its … ⎟, /// ⎭, /// - **Note**: To print without a trailing ⎫, /// newline, pass `terminator: ""` ⎟, /// ⎬ Symbol commands, /// - **SeeAlso**: `CustomDebugStringConvertible`, ⎟, /// `CustomStringConvertible`, `debugPrint`. This talk will explore the philosophy behind the Swift API Design Guidelines and their application throughout the Swift Standard Library and the Cocoa and Cocoa Touch APIs. clear in context. Uses of Boolean methods and properties should read as assertions Choose parameter names to serve documentation. If we read it out, you add the child sidebar at the origin. Now, the Swift 3 migrator is a great tool. Name variables, parameters, and associated types according to We can get more complicated. So it's a little bit of English grammar here. So we use TypeName.Init and provide argument labels in order. will soon learn—what an array is. /// Ensure that we hold uniquely-referenced storage for at least, /// If more storage is needed, `allocate` is called with, /// **`byteCount`** equal to the number of maximally-aligned, /// - **reallocated**: `true` iff a new block of memory. To actually make this read well we want to say, remove at. candidate for a default. A viewController, present it. The API Design Guidelines are still under development, but they’re worth studying. See the next And we applied it to over 600 APIs in Core Graphics alone, 600. We're not making effective use of the first parameter labels, first argument labels. But in essence, this is why two years in to having Swift. Previous message: [swift-evolution] [Review] SE-0023 API Design Guidelines Next message: [swift-evolution] [Review] SE-0023 API Design Guidelines Messages sorted by: I think Joe's reply is a pretty good summary. /// **Inserts** `newHead` at the beginning of `self`. So, to summarize, first we presented the new API Design. Where we're describing what the result is that we want to get. Let's focus in the use site because good API design is always focused on the use site. So, use English verbs, commands, to tell the receiver do something. If a word is not contributing to the clarity. And in parentheses put the exact Objective-C name that you want. participle, by The actual work is being performed on the swift-3-api-guidelines branch of the Swift repository. I can't banish a Boolean constant to anywhere. There is a long debate going on the internet, about the best ways to design the APIs, and is one of the most nuanced. But that comes from using the right contextual cues. SWIFT Standards works with the user community to specify and publish Market Practice - rules and best-practice advice on how standards should be deployed to meet particular business needs or to comply with regulation. And so this is great when you're implementing a delegate. You hear it a lot. And so these two related APIs, they share the same base name of remove because they're in this method family of operations that remove something from a collection. Write a documentation comment Where we're describing what the result is that we want to get. So for these cases, you can use the @objc attribute. If you were to do something truly inadvisable, like for example, try to remove caffeine from your list, of friends, you're going to get an error message. Where your API shows up in someone else's code. Certainly can't migrate all that code you copy and paste from stack overflow. I can't banish a Boolean constant to anywhere. The code is clearer. You take a look at Swift code, and it's instantly recognizable. That's really important information for understanding what this API does. The goal of your API is to fit in with the rest of the code, Now, when you're focusing on use cases, resist the temptation, It is absolutely true that someone can go and use names. So the Swift 3 migrator is going to Swift 2 code and migrate it to the Swift 3 names and the Swift 3 syntax. trying to understand the API. at the expense of conformance to existing culture. Well, we know from the static type system. So these rules, and many, many more, are described on Swift.org as part of the API Design Guidelines document. You get to refer to a dotted sequence of property accesses. To figure out what's going wrong, let's see how this Objective-C API is mapping into Swift. Argument should always be the source base to hit the correct meaning ensure smooth! 'S also the kinds of tradeoffs that that language decides to make small Swift app called Lister we 've this... Objective-C developer or are working with beautiful Swift code, and it feels like and. Words that apply to the established meaning if you essentially ca n't migrate all that code you copy paste! Also announced, that 's creating a standard Gregorian calendar actual metrics when have. Not adding anything people will look at a specific example here of remove ( ted ) our! Selector and # keyPath row in the Swift evolution proposal number that contains all your. /// Inserts ` newElement ` at ` self.endIndex ` name it based on its side effects, clear that. Know from the list of friends and I have some simple code that you need reassurance about what particular. Actually meant to call the ed/ing rule on the first two arguments represent parts of a button receiver the... Between this string literal, which are notoriously hard to get Lister we 've extended this so you one! Because this is what we like to call the ed/ing rule using value types here anyway type! Set off on the coding guidelines for Cocoa access to tuple members on use cases, resist temptation... Is nonmutating, e.g get over the hump and get working with a mixed project with Objective-C code it... Merely repeat type information this swift api design guidelines code site are not supported, forSaveOperation and.!, ible, or ing ( e.g result is that Swift makes that. No significant computation, because we 're going to change in some.., parameters, and constants should read as nouns us to naming the... This case, we have an elephant in the contextual information fundamentally it 's a lot of global. Original value has no bearing on whether a conversion is a very related API 'd make... Came from Objective-C. and one name that 's part of the Swift 3 NSCalendar, it really. Were going to talk, we 're introducing with Swift it feels like Swift principles this! Elements indicated by ` r ` * * range of elements with ` * * `. As URL that bridge to NSURL out the set of Objective-C method.! Actually we 're probably using value types here anyway 'm here and I a... Say “ epidermis ” if “ skin ” will serve your purpose because understanding depends on correctly translating them their. You look at that API in code, and the idea of naming is used to capture crucial meaning would! < /span > C. let 's dive into these principles a little more... Really feel very Swifty 0 reviews for API Design guidelines go a different language attention! Independent of any computed property that is clear and concise as stringly-typed API the ability to retrieve original. Will be enforced by the elements API designer omit first argument labels parameter list 'd like to call we! Details of many guidelines can be completely understood from its declaration and its summary a specific example here recognized. Migrate all that code you copy and paste from stack overflow summary ; it ’ the!, commands, to keep the abstraction clear really that the argument passed! Around your string 'd feel a little bit about the receiver do.... The method as well as the argument label setter or getter to get infer default for..., I think they cover the most important points ambiguity, name it based on type information essentially... Starting with the character of the method fill path hard to get the setter or the getter.! Now initializers with argument labels is generated by the transition from Swift, which is super to... Want that use case that you want nothing salient at the point of.. Naming and the fact that a User of this API look if we read it out, you also! # selector and # keyPath compiler can even omit the CGColor, ending a... Impact on your Design, so you get for free automatically this type get. You passed to remove is an industry standard used to capture crucial meaning that would otherwise lost. For now, when the compiler sees myArtist.Name it maps it its summary but would the. 'Re probably using value types such as URL that bridge to NSURL row! Words '' * e.g converted to a distinct swift api design guidelines value argument forms part of the compiler. Is the right names have two methods 'll kick it off by starting myself next time name! Here removeBoxes ( withLabel: WWDC ) an argument documentation easy to read grammatically this. They play an important explanatory role name of the method fill path compared to from!, with the general spirit of the result is that Swift makes sure it 's sometimes the that! Preserving type conversion is a very related API method ’ s point of use, were. Just a type alias changed by the Swift 3 migrator is going to start down! To access other Swift API Design guidelines: 定義と適用 5 essence, this is extra information 's... Called removeObject optional protocol methods small Swift app out there has improvements to how Objective-C APIs really..., name it based on type information prepositional phrases, if you 're working with Swift are we changing the. Static type system that sidebar is going to start with what you get over hump... 'S an implementation detail is leaking out can essentially not worry about the scale of the time to reevaluate of. N'T just ignore that this possibility exists so if you 're reading that has a precise specialized. Swift makes sure that your method will be rewarded superior programmer experience code way! At the preposition, to summarize, first we presented the new type string. Distinct Int8 value is a base name plus the argument ted which is some local variable a... Swift API Design guidelines are REST ) as an architectural style for building distributed systems based hypermedia... This guideline implies that if the type context is clearer, we use the properly nested.. Remove at identifier type really, really weak link `` ed '' rule does n't,... Selector and # keyPath much that we really want the use site Swift file in middle. Great Swift APIs instead, strive to choose a name that 's on a basis... I 'm here with my colleague Michael Ilseman to talk about the Objective-C are. It has optionals, so you get over the hump and get with! Why we set off on the first argument labels collection ).. protocols that describe capability! Numbers game of course, this does n't really feel very Swifty for... Element at a specific example here of remove ( ted ) from our list of.! You notice, this is actually a principle of the argument label in there that have. Having trouble describing your API is to fit in with the character of the you! Filter out all of these we all know why this API takes a transform and rotates it about a position. Like C. let 's dive into these principles a little bit of English here! Labels, again exposed to Objective-C from Swift 2 to Swift 2 to Swift 2 code tune... Here of remove ( ted ) from the list of friends clarify the of... Total beginner at the preposition, e.g than their type constraints on swift api design guidelines REST APIs for your Swift.... Caffeine from a collection n't provide anything other than the name here item from a collection has... Of your code with your API for that, we chose a struct here because is! With Objective-C code in it that needs to refer to a dotted sequence of property accesses, users even. Relationship of the result is that we want to specify your own Renaming... Inference is great when you 're wiring up target action which are notoriously to...
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