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I used classes reference types to subclass UIView in all the above UIKit-based helper protocols. Years ago, professors, coworkers, mentors, fellow developers, etc., had been talking about techniques like: never writing a function that doesnt fit on one screen without scrolling (i.e., no longer than one printed page, and preferably shorter); breaking large functions into smaller ones; breaking large code files into smaller ones; using meaningful variable names; taking time for design before banging on a keyboard; making judicious and consistent use of spacing and indentation; the grouping of related properties and behaviors into classes and/or structs; and, grouping related classes and/or structs into organizational units like frameworks or libraries. Can you honestly say you understood this code after taking a glance at it? Learn how to code in Swift and build a real world app from scratch. For more on protocol extensions read, I suggest you give a read through the entire language guide. I thought this was old news. Many Swift developers describe the language as being protocol-oriented, but what does that really mean? What's the correct way to implement default properties when doing default implementation of protocols in Swift? Some might say that the only real difference between the two is that in protocol-oriented programming (POP) we prefer to build functionality by composing protocols (this new struct conforms to protocols X, Y, and Z), whereas in object-oriented programming (OOP) we prefer to build functionality through class inheritance. For more information about protocol-oriented programming, you should watch Dave Abrahams talk at WWDC that introduced the topic: https://developer.apple.com/videos/play/wwdc2015/408/. Get the visibility you need to understand your apps performance and speed up the debugging process. Compare the class inheritance hierarchy for UIButton, that I showed you earlier, to the protocol inheritance bloat of the Swift Array: Local reasoning cant apply to either of these complex entities. On the other hand, protocols can adopt from one to many other protocols. I believe many of the core frameworks we use are still written in Objective-C (and some C++ and C), like Foundation and UIKit. @Alexander I'd argue that the framing of OOP above is focused on single inheritance. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Look at the top view in the ani-GIF shown here: Im very proud of the minimal amount of POP code I had to write to create fully-functional and generic stack and queue data structures that Im now using in my own apps. Reference semantics can lead to unintended sharing of data by class instances (references). AppCoda is one of the leading iOS programming communities. Remember one very important point: Most code in the iOS (and OS X) SDKs comes in the form of class hierarchies. My goodness. // ensure NO ivars of self are actually captured, // Most cocoa classes will emit their own inner pointer buffers instead of traversing this path. What happens if I accidentally ground the output of an LDO regulator? Instead of regurgitating and defining them, Ill list them here and provide a link to the detailed explanation I wrote about OOP as materialized in Swift here. I believe the ambiguity is removed now. I hope you can read each as they dont contain much code, but are powerful nonetheless. Thus, with POP, value types have become first class citizens in Swift. Kindly can you elaborate more, I think you have got the main idea. They are the secret sauce that makes Swift POP so powerful. Objective-C uses the term protocol instead of interface, and protocols can require methods and properties, but only a class can adopt a protocol, not a struct. ), but it's fundamentally still the same meaning of "protocol" as in ObjC. The actual type to use for that associated type isnt specified until the protocol is adopted. I then called one of the protocols methods. That means Ive got to be able to call the UIView initializer, too. This allows you to define behavior on protocols themselves, rather than in each types individual conformance or in a global function. Protocol Oriented Programming is mostly the same as OOP but it pays additional attention to functionality sharing not only via inheritance but also via protocol adoption (Composition over inheritance). Here break, acceleration may be common method among three subclass but not the flyable method of airplane. How to implement SOLID principles into an existing project. OOP benefits include reusability, inheritance, maintainability, hiding complexity (encapsulation), abstraction, polymorphism, access control to a class, and access control to a classs properties and methods. There are no perfect solutions. Making statements based on opinion; back them up with references or personal experience. Protocol polymorphism Were avoiding side effects due to unintended mutation because Every variable has an independent value, and references to that value arent shared., Since the Swift struct is a value type and can adopt protocols, and Apples pushing POP over OOP, there you have the reasoning behind the companys evangelization for protocol(s) and value oriented programming.. // SAFETY: Constrain "addBorder" only to UIViews. He has a strong background in C#, C++, .NET, JavaScript, HTML, CSS, jQuery, SQL Server, Agile, TDD, Git, and other technologies. Multiple inheritance can get very messy very quickly. Lets talk a little comparative languages before I answer my own question. Of course this applies to all types that use value semantics. >>, Paul Hudson @twostraws May 28th 2020. If looking at some code and understanding it takes more than 5 minutes, then I know it doesnt fall under the category of Apples local reasoning principle. Say I want several instances of UIView to all have the same background color. My time is precious and I dont have a lot to spare for ivory tower theorizing. (Theyre pushing one more ideal related to POP, as well see below.) What do we call that? and M.Sc. He earned a B.Sc. Youll see lots of protocols, links to protocol definitions, and diagrams of protocol inheritance. Ive chosen to show you how to extend or enhance whichever term you prefer UIKit classes because 1) youre probably so used to dealing with them and 2) its a bit more tricky to extend iOS SDK classes like UIView than it is if you were starting from your own custom classes. For example, a Car drives, stores cargo, seats passengers, plays music, etc. For example, when you pass an array to a function, that function cant accidentally modify the callers copy of the array. These are many functionalities that are each quite distinct, but they all get indivisibly lumped into the Car class. Theres a cost to adding configurable properties to my protocol. Protocol Oriented Programming and the Delegate Pattern. For Swift POP is an improved version of OOP. I somehow doubt this is many of my readers most pressing concern right now. Extending its functionality? Visually, it looks like this: The merits of OOP have been long extolled. As I mentioned in the last article, Apple is evangelizing for the related concepts of POP and value semantics. Enums could be implemented by classes too. Dont start with a class. Ancestor classes tend to be buckets for new functionality; oftentimes they become polluted or bloated with too many, extra, extraneous, and/or unrelated features. Show that involves a character cloning his colleagues and making them into videogame characters? Its good for you to know a bit about other languages as you may find yourself at some point, for example, linking C++ libraries into your iOS apps. Are you losing sleep over it? These interfaces and the Objective-C protocol dont implement anything, they just specify requirements, serving as blueprints for the adopting classes and/or structs. Today, well discuss why Swift is considered a protocol-oriented language, compare POP and object-oriented programming (OOP), compare value semantics and reference semantics, consider local reasoning, implement delegation with protocols, use protocols as types, use protocol polymorphism, review my real-world POP Swift code, and finally, discuss why Ive not bought 100% into POP. This is best explained with an example and picture: Notice my comment in the SimpleUIViewWithBorder immediately above in the class definition. Can someone please elaborate what exactly is protocol oriented programming, and what added value does it bring? Classes provide single inheritance and struct doesn't support inheritance. You can see instances of these struct types at work in the Xcode 9 playground shown below. The WWDC video itself is a bit advanced and requires more breadth. Privacy Policy By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 2022 All rights reserved. The designers of Swift used the opportunity of developing a new language to rethink the kinds of design patterns they want to embrace. When large class hierarchies are built, a lot of properties and functionality can get inherited. We rely on new concepts: protocol extensions, protocol inheritance, and protocol compositions. While in protocol oriented programming in swift: So protocol oriented programming is nothing but just an another programming paradigm that try to solve the OOP drawbacks. Subclassing gave me direct access to everything in the parent UIView class, making my code clear, short, simple, and readable. Our aim is to teach everyone how to build apps with high quality and easy-to-read tutorials. Console output from previous code snippet. Swift just added new features to protocols (protocol extensions, protocol generics, etc. It is Apple thing so I mainly differ it from Objc 2. I cant. In Swift you could also adopt as many protocols as you want. Asking for help, clarification, or responding to other answers. When adding a new disk to RAID 1, why does it sync unused space? The book uses a problem-solution approach to discuss the APIs and frameworks of iOS SDK. When to use In OOP suppose we have a vehicle base class which is inherited by the airplane, bike, car etc. Protocols were important in iOS even before Swift. I have read this and watched the Protocol-Oriented Programming in Swift video, but coming from an Objective-C background still haven't understood it. Refund Policy - difference between super().__init__() and explicit superclass __init__(), Aspect Oriented Programming vs. Object-Oriented Programming. Protocol as a key point of OOP concept. From Apple's own website: "At the heart of Swift's design are two incredibly powerful ideas: protocol-oriented programming and first class value semantics.". Ah, er, ah Has that ever happened to you? Yeah, yeah, yeah, Swift is open source, but Apple makes big money from the App Store and apps are what makes all of Apples devices useful, and many, many app developers are moving to Swift. What are the "disks" seen on the walls of some NASA space shuttles? It takes time, practice and experience. I see some problems with POP just as I do with many other technologies, even OOP. They're design paradigms that are greatly related. Associated types are specified with the associatedtype keyword. In one of the WWDC videos on POP, an engineer/presenter says we have a saying in Swift. 3. An example of this class is shown as the red colored bottom view in the image I just presented above. Does functional programming replace GoF design patterns? Implementator of protocol one should implements all from first and the second protocols, value type implement protocol(as usual reference type), memory leak, incorrect data stored,race condition to access in complex multi-thread environments, can be large by inheriting members of super classes at chain time, is value type - each time a fresh copy is made when needed, provides multi inheritance - inherits protocols, Defines what Methods, Properties and Initializes are required o Can Glossary They play a leading role in the structure of the Swift standard library and are a common method of abstraction. If you havent read the introductory article, please do so before continuing onwards. From Apple: Protocols can be extended to provide method, initializer, subscript, and computed property implementations to conforming types. Protocols as types A number of my iOS and OS X apps link with C++ libraries as I have Windows versions of those apps. Each of these helper protocols is standalone. Do not depend upon concretions. You may have had this feeling before and thats just a name for that feeling. Avid and well-published author and software developer now specializing in iOS mobile app development in Objective-C and Swift. So in general POP is a one of the versions of OOP if we speak about programming paradigms. Its is hard to support class inheritance. Value semantics allow us to avoid unintended changes to variables, which is a really good thing. 3. *POP lets you to add abilities to a class or struct or enum with protocols which supports multiple implementations. It can be used by not only class, but also. I would have lost a lot of granular control. Descendants of Car, such as Ferrari, Toyota, BMW, etc. SPONSORED Whether it is Application Performance Monitoring, Crash Reporting or Bug Reporting, Instabug has your back. Sometimes I use those container views ornamentally (visibly) to improve to look, feel, and layout of my UI. I didnt. As I develop new code, or refactor existing code, Ill consider making the leap on a case-by-case basis. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. For example, maybe when you just joined a new team and you have tons of code to look at but very little context, can you understand whats going on in that single function? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The consequence of this is that there is reduced code reuse. However, even that is dubious because OOP developers also usually prefer composing functionality to inheriting it its just easier to maintain. WWDC22 SALE: Save 50% on all my Swift books and bundles! This smells like a contrived problem cooked up to be supposedly looking for a POP solution.