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J2ObjC
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J2ObjC vs Swift: What are the differences?

Developers describe J2ObjC as "Java to iOS Objective-C translation tool and runtime used by Google Inbox to share 70% of its code across Android, iOS, and Web". J2ObjC is an open-source command-line tool from Google that translates Java code to Objective-C for the iOS (iPhone/iPad) platform. This tool enables Java code to be part of an iOS application's build, as no editing of the generated files is necessary. The goal is to write an app's non-UI code (such as data access, or application logic) in Java, which is then shared by web apps (using GWT), Android apps, and iOS apps. On the other hand, Swift is detailed as "An innovative new programming language for Cocoa and Cocoa Touch". Writing code is interactive and fun, the syntax is concise yet expressive, and apps run lightning-fast. Swift is ready for your next iOS and OS X project — or for addition into your current app — because Swift code works side-by-side with Objective-C.

J2ObjC and Swift are primarily classified as "Cross-Platform Mobile Development" and "Languages" tools respectively.

"Backed by Google" is the primary reason why developers consider J2ObjC over the competitors, whereas "Ios" was stated as the key factor in picking Swift.

J2ObjC and Swift are both open source tools. It seems that Swift with 48.4K GitHub stars and 7.76K forks on GitHub has more adoption than J2ObjC with 5.47K GitHub stars and 771 GitHub forks.

What is J2ObjC?

J2ObjC is an open-source command-line tool from Google that translates Java code to Objective-C for the iOS (iPhone/iPad) platform. This tool enables Java code to be part of an iOS application's build, as no editing of the generated files is necessary. The goal is to write an app's non-UI code (such as data access, or application logic) in Java, which is then shared by web apps (using GWT), Android apps, and iOS apps.

What is Swift?

Writing code is interactive and fun, the syntax is concise yet expressive, and apps run lightning-fast. Swift is ready for your next iOS and OS X project — or for addition into your current app — because Swift code works side-by-side with Objective-C.
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    Jobs that mention J2ObjC and Swift as a desired skillset
    OneSignalOneSignal
    San Mateo, California
    What companies use J2ObjC?
    What companies use Swift?

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    What tools integrate with J2ObjC?
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    What are some alternatives to J2ObjC and Swift?
    React Native
    React Native enables you to build world-class application experiences on native platforms using a consistent developer experience based on JavaScript and React. The focus of React Native is on developer efficiency across all the platforms you care about - learn once, write anywhere. Facebook uses React Native in multiple production apps and will continue investing in React Native.
    Ionic
    Free and open source, Ionic offers a library of mobile and desktop-optimized HTML, CSS and JS components for building highly interactive apps. Use with Angular, React, Vue, or plain JavaScript.
    Xamarin
    Xamarin’s Mono-based products enable .NET developers to use their existing code, libraries and tools (including Visual Studio*), as well as skills in .NET and the C# programming language, to create mobile applications for the industry’s most widely-used mobile devices, including Android-based smartphones and tablets, iPhone, iPad and iPod Touch.
    Flutter
    Flutter is a mobile app SDK to help developers and designers build modern mobile apps for iOS and Android.
    Apache Cordova
    Apache Cordova is a set of device APIs that allow a mobile app developer to access native device function such as the camera or accelerometer from JavaScript. Combined with a UI framework such as jQuery Mobile or Dojo Mobile or Sencha Touch, this allows a smartphone app to be developed with just HTML, CSS, and JavaScript.
    See all alternatives
    Decisions about J2ObjC and Swift
    StackShare Editors
    StackShare Editors
    Angular
    Angular
    jQuery
    jQuery
    Objective-C
    Objective-C
    Swift
    Swift
    Go
    Go
    Ruby
    Ruby
    Java
    Java
    React
    React
    Python
    Python
    Node.js
    Node.js
    Rails
    Rails

    By mid-2015, around the time of the Series E, the Digital department at WeWork had grown to more than 40 people to support the company’s growing product needs.

    By then, they’d migrated the main website off of WordPress to Ruby on Rails, and a combination React, Angular, and jQuery, though there were efforts to move entirely to React for the front-end.

    The backend was structured around a microservices architecture built partially in Node.js, along with a combination of Ruby, Python, Bash, and Go. Swift/Objective-C and Java powered the mobile apps.

    These technologies power the listings on the website, as well as various internal tools, like community manager dashboards as well as RFID hardware for access management.

    See more
    StackShare Editors
    StackShare Editors
    Objective-C
    Objective-C
    Gradle
    Gradle
    Swift
    Swift
    Java
    Java

    At the heart of Uber’s mobile app development are four primary apps: Android rider, Android driver, iOS rider, and iOS driver. Android developers build in Java, iOS in Objective C and Swift. Engineers across both platforms land code into a monolithic code base that ships each week.

    They use some third-party libraries, but often build their own, since “Many open source libraries available are general-purpose, which can create binary bloat. For mobile engineering, every kilobyte matters.”

    On Android, the build system is Gradle. For the UI, Butter Knife binds views and callbacks to fields and methods via annotation processing, and Picasso provides image loading.

    As for iOS, all of the code lives in a monorepo built with Buck. For crash detection, KSCrash reports crashes to the internal reporting framework.

    See more
    Conor Myhrvold
    Conor Myhrvold
    Tech Brand Mgr, Office of CTO at Uber · | 8 upvotes · 422.4K views
    atUber TechnologiesUber Technologies
    RIBs
    RIBs
    Swift
    Swift
    Objective-C
    Objective-C

    Excerpts from how we developed (and subsequently open sourced) Uber's cross-platform mobile architecture framework, RIBs , going from Objective-C to Swift in the process for iOS: https://github.com/uber/RIBs

    Uber’s new application architecture (RIBs) extensively uses protocols to keep its various components decoupled and testable. We used this architecture for the first time in our new rider application and moved our primary language from Objective-C to Swift. Since Swift is a very static language, unit testing became problematic. Dynamic languages have good frameworks to build test mocks, stubs, or stand-ins by dynamically creating or modifying existing concrete classes.

    Needless to say, we were not very excited about the additional complexity of manually writing and maintaining mock implementations for each of our thousands of protocols.

    The information required to generate mock classes already exists in the Swift protocol. For Uber’s use case, we set out to create tooling that would let engineers automatically generate test mocks for any protocol they wanted by simply annotating them.

    The iOS codebase for our rider application alone incorporates around 1,500 of these generated mocks. Without our code generation tool, all of these would have to be written and maintained by hand, which would have made testing much more time-intensive. Auto-generated mocks have contributed a lot to the unit test coverage that we have today.

    We built these code generation tools ourselves for a number of reasons, including that there weren’t many open source tools available at the time we started our effort. Today, there are some great open source tools to generate resource accessors, like SwiftGen. And Sourcery can help you with generic code generation needs:

    https://eng.uber.com/code-generation/ https://eng.uber.com/driver-app-ribs-architecture/

    (GitHub : https://github.com/uber/RIBs )

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    StackShare Editors
    StackShare Editors
    Apache Thrift
    Apache Thrift
    Kotlin
    Kotlin
    Presto
    Presto
    HHVM (HipHop Virtual Machine)
    HHVM (HipHop Virtual Machine)
    gRPC
    gRPC
    Kubernetes
    Kubernetes
    Apache Spark
    Apache Spark
    Airflow
    Airflow
    Terraform
    Terraform
    Hadoop
    Hadoop
    Swift
    Swift
    Hack
    Hack
    Memcached
    Memcached
    Consul
    Consul
    Chef
    Chef
    Prometheus
    Prometheus

    Since the beginning, Cal Henderson has been the CTO of Slack. Earlier this year, he commented on a Quora question summarizing their current stack.

    Apps
    • Web: a mix of JavaScript/ES6 and React.
    • Desktop: And Electron to ship it as a desktop application.
    • Android: a mix of Java and Kotlin.
    • iOS: written in a mix of Objective C and Swift.
    Backend
    • The core application and the API written in PHP/Hack that runs on HHVM.
    • The data is stored in MySQL using Vitess.
    • Caching is done using Memcached and MCRouter.
    • The search service takes help from SolrCloud, with various Java services.
    • The messaging system uses WebSockets with many services in Java and Go.
    • Load balancing is done using HAproxy with Consul for configuration.
    • Most services talk to each other over gRPC,
    • Some Thrift and JSON-over-HTTP
    • Voice and video calling service was built in Elixir.
    Data warehouse
    • Built using open source tools including Presto, Spark, Airflow, Hadoop and Kafka.
    Etc
    See more
    SVN (Subversion)
    SVN (Subversion)
    Git
    Git
    JSON
    JSON
    XML
    XML
    Python
    Python
    PHP
    PHP
    Java
    Java
    Swift
    Swift
    JavaScript
    JavaScript
    Linux
    Linux
    GitHub
    GitHub
    Visual Studio Code
    Visual Studio Code

    I use Visual Studio Code because at this time is a mature software and I can do practically everything using it.

    • It's free and open source: The project is hosted on GitHub and it’s free to download, fork, modify and contribute to the project.

    • Multi-platform: You can download binaries for different platforms, included Windows (x64), MacOS and Linux (.rpm and .deb packages)

    • LightWeight: It runs smoothly in different devices. It has an average memory and CPU usage. Starts almost immediately and it’s very stable.

    • Extended language support: Supports by default the majority of the most used languages and syntax like JavaScript, HTML, C#, Swift, Java, PHP, Python and others. Also, VS Code supports different file types associated to projects like .ini, .properties, XML and JSON files.

    • Integrated tools: Includes an integrated terminal, debugger, problem list and console output inspector. The project navigator sidebar is simple and powerful: you can manage your files and folders with ease. The command palette helps you find commands by text. The search widget has a powerful auto-complete feature to search and find your files.

    • Extensible and configurable: There are many extensions available for every language supported, including syntax highlighters, IntelliSense and code completion, and debuggers. There are also extension to manage application configuration and architecture like Docker and Jenkins.

    • Integrated with Git: You can visually manage your project repositories, pull, commit and push your changes, and easy conflict resolution.( there is support for SVN (Subversion) users by plugin)

    See more
    Interest over time
    Reviews of J2ObjC and Swift
    Avatar of Bessalitskykh
    Software Development Consultan at MLSDev Inc.
    Review ofSwiftSwift

    The performance of Swift is almost the same as that of C++, which is considered the fastest in algorithm calculation arithmetics. Apple had this idea in mind and worked to improve the speed of Swift. For example, Swift 2.0 has beaten C++ in several computation algorithms, such as Mandelbrot algorithm. Objective-C is slower because it contains C API legacy.

    Swift is faster than Objective-C, because it removed the limitations of C language and has been improved with the help of advanced technologies that were unavailable when C was developed. As mentioned by Apple, Swift was originally designed to operate faster.

    Despite the fact that languages are different, they both integrate, and work with Cocoa and Cocoa Touch APIs, for all Apple platforms. Therefore, a regular app-user would not recognize the difference in operating speed between Objective-C vs Swift. Speed also depends on a programmer’s level and capabilities, since a slow app can be written in Swift as well.

    Learn more here https://mlsdev.com/blog/51-7-advantages-of-using-swift-over-objective-c

    Avatar of gistya
    iOS Developer at JORY
    Review ofJ2ObjCJ2ObjC

    This is one of the most amazing open source projects out there. Tom and Kieth do an amazing job working with the developer community and quickly responding to questions and concerns. I was blown away by how solid the ported code was. What a life-saver and a ridiculously awesome tool.

    Avatar of Bessalitskykh
    Software Development Consultan at MLSDev Inc.
    Review ofSwiftSwift

    Its performance approaches the one of C++ which is considered the fastest algorithm calculation arithmetics. And Apple strives to improve the speed of Swift. Learn more here https://mlsdev.com/blog/51-7-advantages-of-using-swift-over-objective-c

    How developers use J2ObjC and Swift
    Avatar of Lawrence Cheuk
    Lawrence Cheuk uses SwiftSwift

    iPhone app, a new born language, it may good but the IDE, xcode is bad compare with Visual Studio. It just like a baby. playground can only use without connect to other library...you can not do a simply refactor of renaming a variable. You can go to definition and find reference, but you can not go to implementation....I should write them on xcode not here basically it is not the fault of swift, but it tightly to it, unless you want to use a notepad to write it.

    Avatar of Refractal
    Refractal uses SwiftSwift

    Most of our newer apps are written completely in swift, with our older ones and some special cases using a mix of Swift and Objective-C, but with Swift 2, the language is pretty much a must-use. "guard" is <3.

    Avatar of fileee GmbH
    fileee GmbH uses J2ObjCJ2ObjC

    We use J2Objc and GWT to provide a shared library of cross-platform code that is used on all our client platforms (Android, iOS and the web) and even in the backend.

    Avatar of Flutter Health Inc.
    Flutter Health Inc. uses SwiftSwift

    Flutter is coded with Swift v.2.3 and can be run with Xcode v.8.2.1. To launch in Xcode 9.3, the code needs to be migrated to Swift 4.1

    Avatar of Maxim Ananov
    Maxim Ananov uses SwiftSwift

    Most of the app code was gradually rewritten in Swift for better performance and code maintenance.

    Avatar of JINJA Ltd.
    JINJA Ltd. uses SwiftSwift

    Our native iOS app is built on Swift, and most of the basic function is still written in Swift

    How much does J2ObjC cost?
    How much does Swift cost?
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    Pricing unavailable
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