Swift code is compact compared to Objective-c, but that is not a goal in API Design. It's more important than having brief code. And so this follows from English grammar. Now, method names will get you a long way towards a Swifty API, but this doesn't quite go far enough. takes a transform and rotates it about a given offset. 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. 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. And it describes the relationship of the argument. That is, when the compiler sees myArtist.Name it maps it. malifischerlevine1 added API Design Guidelines in Swift to Delivered Board Treehouse iOS Content Roadmap. So we've extended NS Swift Name. Everyone is an API designer. API Design Guidelines in Swift - Learn valuable skills with this online course from Treehouse And so we write out a use case. Here ArtistGetName, ArtistSetName are now just the getters and setters for the computed property Artist. those would instead be static properties. /// is generated by the expression `String(x)`. But if you look at this, this doesn't really feel very Swifty. Now, when you're focusing on use cases, resist the temptation to optimize for bad code. So it's just actively wrong. uses. Prefer to locate parameters with defaults toward the end of the like A and B and C for all the variables. Basically every Swift file in the entire project is changed by the transition from Swift 2 to Swift 3. For example, conversion from Int8 to Int64 is value about that particular change to the Swift language. Maybe we'd feel a little bit more comfortable. And the fact that this API takes a string, that kind of allows simple errors. many of these same techniques I presented today. What do we write here? So in this case, we have two methods. But you should only do this when the APIs have the same semantics. its summary. ambiguities in the presence of type inference. explicitly. And we've been applying these to thousands upon thousands of APIs over more than a decade, all right, to produce the Cocoa and Cocoa Touch platforms. But they differ basically in how they treat their argument. 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. They're trying to describe the argument. with Fix-its to update your code so you can get moving faster. Has one name that's appropriate for Objective-C. and one name that's appropriate for Swift. Focus on the summary; it’s the most important part. And then there's the argument ted which is some local variable with a type. Thank you to David James for spotting this! Stick to the established meaning if you do use a term of art. It's a compound made up of elements. Now, we chose a struct here because this is extensible. monomorphism, i.e. Well, we know from the static type system. And so now this reads -- And so now this reads nice, natural and Swifty. for every declaration. We're going to talk about the philosophy behind these guidelines. The main principles of the Swift API design guidelines are. And think about the words that apply to the arguments. Because what is your mind doing as you're reading. So for these cases, you can use the @objc attribute. Additionally, we've put in near miss detection. phrase as the base name: In the following, the API author has tried to create grammatical line1.intersects(line2). (e.g. So if you write or paste in some code from Swift 2, it'll recognize the old API names and give you diagnostics. But I just want to look at how does this look? excellent documentation comments consist of nothing more than a symbol command syntax. But that comes from using the right contextual cues. 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. We hope you enjoy these new APIs. Use the special argument label self in order to tell the Swift compiler what argument to plug the reference to self into. So, we're going to be talking about the Swift API Design Guidelines today. And of course, this @objc with a name works for properties. at some particular point within some main view. So, automatic inference is great and all. If we read it out, you add the child sidebar at the origin. Protocols that describe a capability And the great thing about this, of course. But that comes from using the right contextual cues. Okay? imply to the reader that the method searches for and removes an But these tools will help you get over the hump and get working with Swift 3. All right. See the next It's stating that this argument here will become a child. Now, when we have methods whose primary responsibility is just to return some value we use a noun. When evaluating a design, reading a declaration is seldom sufficient; always examine a use case to make sure it looks clear in context. /// Creates an instance having the specified `value`. 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. * Swift API Design guidelines - "Omit needless words" * e.g. Many or a fundamental type such Int or String, type information and We don't need that extra variable result. The first one transforms a -- takes a transform and rotates it about a given offset. name its mutating counterpart. So, the Swift API Design Guidelines go a different route. Because good API design is always focused on the use site. Labels for Optionally, continue with one or more paragraphs and bullet All right? But the vast majority of times that your API matters, the number of times it's seen, it's going to be in the context of a whole lot of other code. between this string literal, which is super easy to mistype. mostly identical documentation. A good designed API is always very easy to use and makes the developer’s life very smooth. You get to refer to a dotted sequence of property accesses. that this should really just be an initializer. Where we're describing what the result is that we want to get. For all other declarations, describe what the declared entity is. And that corresponds to the mutating form. So, in Swift, a function name is comprised, of so-called base name, which here is remove in both. All of your Objective-C APIs are available in Swift. nouns (e.g. You just write everything in terms of the Swift names and you stay in that set of names. 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. It's also the kinds of tradeoffs that that language decides to make. This is what we jokingly refer to as stringly-typed API. Remember earlier when we created a new calendar identifier type? especially NSCalendarIdentifierGregorian. Arrays are In this case, the act of writing the documentation comment And good API design helps us write code that is clear, concise and beautiful in Swift. And because the type context is clearer, we can even just say .gregorian. I would just say, remove(ted). item for details. Organic compounds, append to it. we apply what we like to call the ed/ing rule. Within a particular programming domain, such as mathematics, a is Any, a single element can have the same type as a sequence of These names have I'm going to start with a couple Objective-C APIs as they were imported into Swift 2. but fundamentally it's driven by heuristics. 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. I talked a little bit about the scale of the Grand Renaming. Animated is true. And so now this reads nice, natural and Swifty. So we have a document directory. Use a single sentence fragment if possible, ending with a can be expanded individually. Often, an API can be completely understood from its declaration and for common Objective-C idioms such as completion handlers. But these don't really express the API Design Guidelines that Doug outlined. #keyPath does exactly what you'd expect. So you get a consistent, whole experience of working, And we've been applying these to thousands upon thousands of APIs, over more than a decade, all right, to produce the Cocoa. Well, we'd probably make a new wrapper type around string to get some strong typing. But essentially it's withLabel. One removes an element by its identity. so when we import them we just change a few strings, Now, Core Graphics is a very popular API that's used. So we can just say, remove(ted) from the list of friends. And so the strong static type system is making sure that the argument you passed to remove is an element of the corresponding collection. Now, when you're coming up with first argument labels, again. It reads really nicely. ambiguities in overload sets. 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. Talk through some of them to try to get a sense of how to build great Swift APIs. It's a lot of change. The entire Swift standard library is being reviewed and updated to follow the Swift API design guidelines. For example: Default arguments are generally preferable to the use of method And we had this for our example here of remove(ted). everything will show you the Swift names. Before, our global variable, which is painfully global, is now a member. Well, for that, we revisit our friend NS Swift Name. Does it skew toward safety, performance? And here what we like to call -- we apply what we like to call the ed/ing rule. Good API design is always focused on the use site. Which is what we like to call the application of these guidelines to all of the APIs you use day to day. Anything that can be exposed to Objective-C from Swift, you can control the name here. You can prefix a Swift name with getter or setter in order to tell the compiler to import this function as a computed property getter or setter. they seemed a little bit out of character. You can get a sense of what the types are just by reading the APIs. to this view argument that is our first argument. Note also that arguments with default values can be omitted, and Clarity is more important than brevity. That is, other modules may want to define their own. But in Swift 3 we support full compound naming. You can also use NS Swift Name in order to nest types. cannot be value preserving: Int64 has more possible values than 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. Whooh! So when we import, we just import it directly. And that includes the base name of the method as well. API Design Guidelines in Swift. start with the following keywords: Include all the words needed to avoid ambiguity for a person used repeatedly. When the operation is naturally described by a noun, use the In practice, this guideline along with those for ⎟, /// - **Parameter terminator**: text to be printed ⎬ Parameters section, /// at the end. Maybe ask your Swift compiler friends on Twitter or something. The only reason to use a technical term rather than a more common in the mind that what we're looking for is terse code. /// **Returns** a `List` containing `head` followed by the elements. And the second function traces a path in red. But what if you're an Objective-C developer or are working with a mixed project? 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. That's misleading. tools such as Xcode give special treatment to bullet items that While it’s easy to think of APIs as something that’s only relevant for SDKs or frameworks, it turns out that all app developers design APIs almost every single day. So, remove item ted from the list of friends. Learn how Swift 3 imports Objective-C APIs and how to expose rich Swift interfaces for existing Objective-C libraries. great summary. Protocols that describe what something is should read as example, foo(bar: nil) and foo() aren’t always synonyms—make So it's a little bit of English grammar here. Write a documentation comment […] And of course, this @objc with a name works for properties, it works for methods, classes, protocols. What is that? Well, it's going to be a CGPoint. Makes sure it's exposed to Objective-C, and computes the correct name. at the expense of conformance to existing culture. when you do care about the Objective-C names. So, when you name a method, name it based on its side effects. Welcome. To decide among them, a user needs to There's the word item that's part of our name. 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