Publication
iOS Animation and Tuning for Efficiency
https://www.toptal.com/developers/ios/ios-animation-and-tuning-for-efficiency
Stefan is available for hire
Hire StefanStefan Progovac
Verified Expert in Engineering
Objective-C Developer
Miami Beach, FL, United States
Toptal member since June 21, 2015
Bio
Stefan is a highly skilled iOS developer with a master's degree in physics. He loves both the technological and artistic sides of software engineering. He's had the pleasure of working on some popular enterprise-level apps used by millions of people for companies like Target, Best Buy, and Roomi. Stefan believes that app development is truly an art.
Portfolio
Yahoo! - Sports
Swift, iOS, SwiftUI
One Up Group LLC dba Play One Up
iOS, Swift, SwiftUI, GraphQL, GraphQL API, UIKit, Real-time Data, Gaming...
PetCo
iOS, Android, Xamarin, CTO, Mobile Development, Mobile
Experience
- iOS - 11 years
- Objective-C - 11 years
- Swift - 9 years
- Bluetooth Low Energy (LE) - 4 years
- Java - 3 years
- Software Architecture - 2 years
- Kotlin - 1 year
Preferred Environment
Objective-C, Swift
The most amazing...
...app I've developed was Cartwheel for Target, an app that has touched so many people.
Work Experience
iOS Developer
2024 - PRESENT
Yahoo! - Sports
- Managed both the iOS Fantasy and Sportacular apps for Yahoo.
- Developed features for these apps used by over 12 million daily users.
- Oversaw launch processes and experiments (like Evaluate).
Technologies: Swift, iOS, SwiftUI
Senior iOS Developer
2026 - 2026
One Up Group LLC dba Play One Up
- Worked as a sole developer and delivered and managed an app that facilitates gaming (live streaming, as well as financial rewards).
- Used Linear to track issues, Firebase for auth and analytics, MoEngage for campaigns, and much more.
- Oversaw app releases to the App Store as well as Test Flight for internal testing. Managed communications with the App Store team.
Technologies: iOS, Swift, SwiftUI, GraphQL, GraphQL API, UIKit, Real-time Data, Gaming, Esports, CI/CD Pipelines, Automated Testing, Claude API
Director of Mobile Apps
2023 - 2024
PetCo
- Managed over 50 developers (iOS, Android, QA) functioning as an interim CTO while the company looked for a new hire.
- Oversaw procedures and processes as well as performance reviews and evaluations.
- Set architectural standards and best practices. Helped plan new roadmaps for other products based on priority and resources.
Technologies: iOS, Android, Xamarin, CTO, Mobile Development, Mobile
iOS Developer
2023 - 2023
Nina Chen
- Built a fashion app from scratch using SwiftUI and leveraging Stripe SDK for payments. All UI components and API layers were custom-built.
- Managed TestFlight and App Store releases. Consulted in best practices and guided the app to the final stages of development.
- Allowed for capturing photos, drag and drop of custom text and images, resizing of photos, and more.
Technologies: iOS, Swift, Mobile Development, React Native, Mobile App Development, SwiftUI, Stripe API, Apple Pay, AVFoundation, Apollo, GraphQL
iOS Tech Lead
2022 - 2023
Scooter's Coffee
- Developed a new version of Scooter's app in SwiftUI from scratch, managing a team of two iOS developers. Oversaw all architectural decisions, set up the CI/CD pipeline using CI/CD pipeline for GitHub, and oversaw provisioning and releases.
- Tracked and fixed stories in Jira, documented procedures in Confluence, used Sketch and Abstract for app designs, and managed image assets.
- Oversaw the design, requirements phase, and building of a new app written in SwiftUI for Scooter's Coffee. Overcame challenges like keeping users logged in from their previous app and interfacing with LevelUp.
Technologies: SwiftUI, Swift, CI/CD Pipelines, Unit Testing
Senior Developer
2022 - 2022
Dexcom
- Wrote a prototype of the G7 App for Dexcom in Flutter, which was used as part of the Food and Drug Administration (FDA) approval process while the flagship app was developing.
- Tracked and fixed issues in Trello and GitHub and used Figma for designs.
- Oversaw the launch and deployment of the prototype in formatives to help train users and regulators, which was an integral part of the FDA approval process.
Technologies: iOS, Flutter
Senior iOS and Swift Developer
2022 - 2022
Swift Medical
- Worked actively on a cutting-edge and innovative healthcare app with a device called Sinatra, connected to the phone via Bluetooth Low Energy (BLE), which takes and analyzes photos of wounds and aids doctors and nurses in tracking progression.
- Contributed to all aspects of the app and created a standalone app that helped the team provision Sinatra devices.
- Completed new features of the app, such as working on bacterial analysis, single-form evaluation, and other thermal imaging analyses for the app.
Technologies: Swift, Core Data, iOS, Bluetooth, AVCaptureSession, Leadership, Video Capture, User Experience (UX), SwiftUI
Senior iOS Developer
2021 - 2022
Catapults Sports LLC
- Worked on instrumental in the live streaming of this sports app, syncing multiple angles to stream effortlessly as the user went from angle to angle.
- Managed the entire CI/CD pipeline, Apple Store account, and release process as a sole developer.
- Fixed numerous issues, usually around video editing, and implemented a caching layer to make streaming more efficient for very long videos and potentially slow internet connections.
Technologies: Objective-C, iOS, C++, C#, Java
Senior iOS Developer
2019 - 2020
Anthem, Inc.
- Helped design the navigation bridge between the iOS-embedded navigation stack and the React Native navigation scheme.
- Worked on device integration; the app tracked steps, sleep, and weight through syncing with HealthKit and more.
- Built accessibility to comply with all federal regulations.
- Provided unit testing and automated builds with Jenkins pipelines.
- Developed push notifications with embedded rich content inside the messages.
Technologies: Kotlin, Java, Objective-C, Swift
Senior iOS Developer
2015 - 2020
AutoLoop, LLC
- Leveraged gelocation for marketing purposes.
- Wrote an entire UI and unit test suite.
- Wrote scripts in Fastlane to fully automate the release—perform screenshots, run all tests, and make releases.
- Built custom UI and animation.
- Wrote an app to facilitate the check-in procedure for car dealers.
Technologies: Objective-C
iOS Developer
2019 - 2019
Latch
- Helped with the reskinning of the UI for the release.
- Worked on debugging issues with Bluetooth connection using BLE protocol.
- Created custom UI components, like piecharts using Core Graphics.
Technologies: Carthage, Core Data, Swift, iOS, Bluetooth Low Energy (LE)
Senior iOS Developer
2015 - 2019
Max2, Inc.
- Worked on a payment module that required Bluetooth interfacing with hardware.
- Formatted ISO 8583 messages intended to securely process payments.
- Developed a chat module leveraging web sockets.
- Worked with remote and in-app notifications.
- Worked with Twitter, FB, and Instagram SDKs. The app promotes social media interactivity.
- Built a custom UI.
- Wrote an app that allows users to search for, view, and rate venues as well as purchase items and do transactions.
Technologies: Objective-C, Swift
iOS Developer
2015 - 2015
Stand Technologies
- Oversaw this project for a small stand-up company from development to release on the App Store.
- Implemented push notifications, including writing server-side code.
- Created a custom networking layer, including efficient categories for image caching and setting UIImageViews, with the ability to cancel or reuse requests if the UIImageView would happen to be reused (such as in a reusable cell) using associated objects.
- Used Facebook APIs for login.
- Created a custom newsfeed using dynamic row heights for added flexibility.
Technologies: Swift
Senior iOS Developer
2015 - 2015
Roomi
- Integrated Parse and Layer to build native chat into the app.
- Worked with Core Animation, Core Text, and CALayer to customize the user experience.
- Used advanced techniques, such as object swizzling, to override default behavior and enhance functionality.
- Worked with Parse's cloud and developed and maintained scripts in JavaScript.
- Worked extensively with push notifications.
Technologies: Core Animation, Parse, Objective-C
iOS Developer
2014 - 2015
Best Buy
- Redesigned and rewrote the entire Best Buy app in Swift.
- Architected the app based on the VIPER paradigm.
- Made use of new Apple technologies such as app extensions and their widgets, primarily for advertisements.
- Experimented with iBeacons. Best Buy was one of the first stores to embed iBeacons into their department store lighting.
- Began working on Apple Pay for a more seamless checkout experience using the Best Buy app.
- Replaced the zBar scanner with a native Apple scanner for barcodes.
- Implemented fast image caching across the application.
Technologies: Swift
Senior iOS Developer
2014 - 2014
ConXus Lochinvar
- Redesigned the UI to look appropriate for the iPhone. Previous developers had only paid attention to the iPad.
- Gained extensive experience with auto layouts of all forms.
- Worked with the Microsoft Cloud and Azure.
Technologies: iOS
iOS Developer
2013 - 2014
Target (Cartwheel)
- Worked on implementing a highly automated environment. Employed a dedicated Jenkins server and Xcode bots and hooks so every Git checkin for the QA would get the latest build to Test Flight.
- Worked with Crashlytics for bug tracking.
- Worked with true Agile methodologies and Jira for efficient work progress.
- Worked extensively with PassKit and CocoaPods.
- Made extensive use of OAuth tokens to guard sessions for items added to cart, as well saved payment information (each having their own tokens).
- Used Google Postman to debug and document RESTful APIs.
Technologies: Objective-C, iOS
iOS Developer
2012 - 2013
Rockwell Collins
- Made extensive use of MapKit and Waypoints for plotting airplane itineraries.
- Made a custom calendar from UICollection View.
- Made extensive use of core data as a kind of cache for data, including using helpful third-party tools like Mogenerator.
- Implemented extensive security features, such as storing in the keychain and various hashing and encryption algorithms.
- Used regular expressions for input validation to prevent SQL injections.
Technologies: Objective-C, iOS
Experience
Cartwheel App
A social savings app for Target. I was one of two developers who rewrote Cartwheel away from the original code base, which was owned by Deloitte. Cartwheel is used by millions of people across the USA.
Best Buy
https://itunes.apple.com/us/app/best-buy/id314855255?mt=8This is the Best Buy store shopping experience app. I was the lead architect in the Swift redesign of the Best Buy app, employing the VIPER paradigm. The project included experimentation with iBeacons and Apple Pay.
SmartLane
https://itunes.apple.com/us/app/smartlane/id686173091?mt=8A dealership app that I am currently maintaining for AutoApp. It is used in Mercedes and Toyota dealerships all across the USA. It allows you to check in and have service on your car, all from the convenience of an iPad.
Ascend Flight Manager
Manage your private jet with this convenient app! This app allows you to create custom flight plans for your private jets. I was the sole developer on this app. It features an immense focus on security, as his clientele base consists of executives for large companies like Coca Cola. I explored the depths of security provided by the Apple OS and was tasked with adding my own custom security options.
Roomi
A app to help people find roommates in cash-expensive markets such as New York City and San Francisco, this app facilitates in-app chat (which I personally developed), paying rent through the app, and browsing room listings
STAND
A social fundraising app to help motivate positive change around the world. Start your own fundraising stands and get your Facebook friends as well as others in the loop. Watch as money is raised for your favorite projects.
Senior Software Developer for Max2
Developed their merchant facing app for iOS in Swift. Worked on the payment module, leveraging Bluetooth, securely formatting messages (using ISO 8583) to securely process payments, app notifications, leveraging websockets, and more.
LATCH
https://apps.apple.com/us/app/latch-app/id1062355375Developed the UI for Latch App including app interfaces (via BLE protocol) with hardware locks that control access to doors for individual customers and businesses alike. I was part of the team that redesigned and implemented a re-branding and new UI.
Education
2009 - 2012
Master of Science Degree in Physics
University of California San Diego - San Diego, USA
2005 - 2009
Bachelor of Science Degree in Mathematics
Michigan State University - East Lansing, USA
Skills
Libraries/APIs
CocoaPods, Parse SDK, Layer API, Apple Maps API, Kiwi, Mantle, Google API, Facebook SDK, jQuery, Core Animation, AVCaptureSession, Stripe API, GraphQL API, Claude API
Tools
Hockey SDK, Crashlytics, GitHub, Git, Jira, Xcode, Slack, Apple Push Notifications, Suds, Pivotal Tracker, Asana
Languages
Swift, XML, Objective-C, JavaScript, Kotlin, Java, Python, C++, C#, GraphQL
Frameworks
OAuth 2, AFNetworking, Core Data, SwiftUI, Flutter, React Native, UIKit
Paradigms
Agile Software Development, Mobile Development, Unit Testing, Automated Testing
Platforms
Bluetooth Low Energy (LE), iOS, Apple Watch, Firebase, Parse, Android, Xamarin, Mobile
Storage
JSON
Other
OAuth, Geolocation, Programming, Freelancing, IT, AVFoundation, Software Architecture, Machine Learning, Augmented Reality (AR), Carthage, Bluetooth, Leadership, Video Capture, User Experience (UX), CI/CD Pipelines, Mobile App Development, Apple Pay, Apollo, CTO, Real-time Data, Gaming, Esports
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