Strahinja Mihajlovic, Developer in Belgrade, Serbia
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Strahinja Mihajlovic

Verified Expert  in Engineering

ChatGPT API Developer

Belgrade, Serbia

Toptal member since December 10, 2019

Bio

Strahinja Mihajlovic is an iOS developer with eight years of experience delivering innovative mobile apps. Specializing in Swift and SwiftUI, he creates clean, user-focused designs. His AI-powered note-taking app, featuring an interactive chat interface, improved user retention by 40%. Strahinja has also built scalable solutions for telecommunication and healthcare clients, driving engagement and optimizing workflows with impactful results.

Portfolio

Mem
SwiftUI, Combine, Apollo, ChatGPT API, SQLite, Large Language Models (LLMs)...
DeepScribe (via Toptal)
Swift, MacOS, Mobile App Development, Mobile Applications, Firebase, iOS SDK...
In the Barn (via Toptal)
Swift, Model View Controller (MVC), Parse, GraphQL, Mobile App Development...

Experience

  • Swift - 8 years
  • SwiftUI - 6 years
  • Combine - 6 years
  • Model View ViewModel (MVVM) - 6 years
  • SQLite - 4 years
  • VIPER Architecture - 3 years
  • ChatGPT API - 3 years
  • Clean Architecture - 3 years

Availability

Part-time

Preferred Environment

Xcode, MacOS, Figma, Mobile App Development, Large Language Models (LLMs), OpenAI, Mobile Applications, iOS SDK

The most amazing...

...project I’ve developed is a chat feature that lets users interact with their notes through AI.

Work Experience

iOS Developer

2021 - 2023
Mem
  • Developed an in-app note-taking editor with markdown, comments, links, media files, and more.
  • Created a share sheet for the app, which handles image sharing, text sharing, and URL sharing.
  • Built almost 100% of the app using only SwiftUI components.
Technologies: SwiftUI, Combine, Apollo, ChatGPT API, SQLite, Large Language Models (LLMs), OpenAI, Mobile App Development, Mobile Applications, ChatGPT, Firebase, Figma, iOS SDK, Deep Linking, Notification Center, Crashlytics, Firebase iOS SDK, UIKit, HTML

iOS Developer

2021 - 2021
DeepScribe (via Toptal)
  • Developed a view that represents live audio input in the form of sound waves.
  • Contributed to a Mac Catalyst app and developed complex UI components that worked on both iPad and Mac.
  • Developed and implemented a complete network layer supporting older API calls.
Technologies: Swift, MacOS, Mobile App Development, Mobile Applications, Firebase, iOS SDK, Deep Linking, Notification Center, Crashlytics, Firebase iOS SDK, UIKit

iOS Developer

2020 - 2021
In the Barn (via Toptal)
  • Rewrote the entire application storyboards to support all mobile and iPad devices.
  • Implemented Google, Apple, and Facebook sign-in methods.
  • Designed and developed ad listing pages for many different ad categories.
  • Implemented native APIs such as geolocation, background fetching, and background uploading.
  • Set up a new architecture to clear the technical debt and established tests and documentation.
Technologies: Swift, Model View Controller (MVC), Parse, GraphQL, Mobile App Development, Mobile Applications, Firebase, Maps, Core Location, iOS SDK, Deep Linking, Notification Center, Crashlytics, Firebase iOS SDK, UIKit

iOS Developer

2019 - 2021
Wireless Media
  • Developed many telecommunication applications for the Balkan region.
  • Rewrote the entire network layer to a SAP back end.
  • Built a custom library for galleries that, apart from photos, supports native video content, YouTube videos, ads, custom views, and more.
  • Developed a custom library for location services that provides an easy way to work with location-related functionalities.
  • Created a mechanism for theme switching on an existing application that works with a system theme and allows other developers to support light and dark-themed versions of future views with ease.
  • Analyzed and later created a plan for analytics that was implemented by the entire mobile team.
  • Developed an entire application in the Combine framework.
  • Created an entire bill payment process that communicates with the bank for telecommunication applications.
  • Developed complex registration processes that worked seamlessly with deep linking and keychain.
  • Handled releases of 10+ applications weekly and spent many hours talking with Apple.
Technologies: RxSwift, Combine, CocoaPods, Swift, Lottie, Push Notifications, Deep Linking, Clean Architecture, SQLite, Mobile App Development, Mobile Applications, Firebase, MapKit, Maps, Location Services and Maps, Core Location, SwiftUI, iOS SDK, Notification Center, Alamofire, Zeplin, Crashlytics, Firebase iOS SDK, Fabric, UIKit, HTML

iOS Developer

2020 - 2020
Camps
  • Provided a framework with flexible high-level features, reducing boilerplate code to a minimum.
  • Developed and optimized most of the UI elements and animations.
  • Performed a high number of UI optimizations so that the app could be installed on a lot of lower-end devices.
  • Designed back-end services that were later implemented in the application.
  • Implemented many external libraries to speed up the development process and meet the deadline.
Technologies: Swift, Model View ViewModel (MVVM), Amazon Web Services (AWS), Push Notifications, Mobile App Development, Mobile Applications, Firebase, Maps, Core Location, iOS SDK, Deep Linking, Notification Center, Alamofire, Crashlytics, Firebase iOS SDK, UIKit

iOS Developer

2017 - 2019
Wireless Media
  • Developed many newsreader applications for the Balkan region.
  • Contributed to the complex video player, which seamlessly integrates inside news applications. It uses AVKit in basic implementation and JWPlayer in some implementations that require video ads.
  • Implemented a continuous integration/continuous delivery system that works with Slack commands, which made it easier for managers/quality assurance engineers to upload builds without developers' help.
  • Rewrote one of the apps entirely from Objective-C to Swift.
  • Implemented deep linking, push notifications, and an ad (banner) system for external links.
  • Implemented both Google (Firebase) and Gemius analytics.
  • Developed a hybrid story page (for a newsreader) that is made in combination with Swift, HTML/CSS, and JavaScript.
  • Built a mechanism that helps with the application localization and localization itself, as most of the applications were multilanguage.
  • Designed and later developed a custom iPad version for one of the applications.
  • Worked with many weather forecast APIs that were used in newsreader applications.
Technologies: RxSwift, Cocoa Touch, CocoaPods, iOS, Lottie-iOS, Jira, Agile Software Development, Git, Push Notifications, Xcode, Swift, SQLite, Mobile App Development, Mobile Applications, Firebase, MapKit, Maps, Location Services and Maps, Core Location, SwiftUI, Firebase Realtime Database, iOS SDK, Deep Linking, Notification Center, Alamofire, Zeplin, Clean Architecture, Crashlytics, Firebase iOS SDK, Fabric, UIKit, HTML

Experience

N1 Info

https://apps.apple.com/us/app/n1-info/id920779491
Rewrote the app from Objective-C to Swift and later built two major versions using MVC and MVVM with RxSwift. Introduced advanced video functionalities, weather forecasts, and improved push notifications, making the app more engaging for users. My contributions helped streamline development processes and significantly enhanced app performance, aligning with modern standards.

Mondo

https://apps.apple.com/us/app/mondo/id673090202
Developed this flagship newsreader app from scratch, integrating advanced video functionalities, reporting features, and a polished user interface. Leveraged my expertise to ensure the app stood out with seamless performance and a user-friendly experience. My work helped establish Mondo as a benchmark for regional news apps.

Story Hr

Crafted this celebrity news app to provide users with real-time updates and personalized recommendations, focusing on intuitive navigation and sleek design to attract and retain users. By implementing a robust back end and thoughtful UX elements, I helped position the app as a go-to platform for celebrity news in Croatia.

Moj mts

https://apps.apple.com/us/app/moj-mts/id957823723
Developed self-care apps for Telekom services across multiple regions, offering features like bill payments, detailed usage statistics, and tariff customization. Implemented user-friendly interfaces tailored to each region’s needs, ensuring accessibility for a diverse user base. My contributions included designing scalable architectures and empowering customers to manage their accounts easily and efficiently.

Moj m:tel

https://apps.apple.com/us/app/moj-m-tel/id1423516571
Developed self-care apps for Telekom services across multiple regions, offering features like bill payments, detailed usage statistics, and tariff customization. Implemented user-friendly interfaces tailored to each region’s needs, ensuring accessibility for a diverse user base. My contributions included designing scalable architectures, which empowered customers to manage their accounts with ease and efficiency.

Mein Mtel Austria

https://apps.apple.com/us/app/mein-mtel-austria/id1091989686
Developed self-care apps for Telekom services across multiple regions, offering features like bill payments, detailed usage statistics, and tariff customization. Implemented user-friendly interfaces tailored to each region’s needs, ensuring accessibility for a diverse user base. My contributions included designing scalable architectures, which empowered customers to manage their accounts with ease and efficiency.

Moj m:tel

https://apps.apple.com/us/app/moj-m-tel/id1251877918
Developed self-care apps for Telekom services across multiple regions, offering features like bill payments, detailed usage statistics, and tariff customization. Implemented user-friendly interfaces tailored to each region’s needs, ensuring accessibility for a diverse user base. My contributions included designing scalable architectures, which empowered customers to manage their accounts with ease and efficiency.

Sportklub

https://apps.apple.com/us/app/sportklub/id1144073831
Maintained and enhanced the app’s functionality, optimizing performance and implementing new features to deliver up-to-date sports news and scores. Focused on improving user engagement by ensuring seamless operation and aligning the app with current sports media trends.

Sasomange

Revamped the app’s core functionality to simplify ad placement for users and improve visibility for advertisers. By optimizing search speeds and implementing a flexible architecture, I enhanced user satisfaction and streamlined workflows. My contributions helped the app scale efficiently and meet the needs of its growing user base.

Mts Biznis

https://apps.apple.com/us/app/mts-biznis/id1301211948
Designed this app for business users, providing them with tools to manage telecommunication services, monitor consumption, and customize tariffs. Focused on simplifying complex processes with intuitive interfaces and efficient back-end solutions. My work empowered users to take control of their accounts while ensuring smooth and reliable app performance.

Camps With Friends

Built a community platform that connects users to local camps and activities, focusing on creating memorable experiences for kids. Worked on back-end integrations and UI optimizations, ensuring the app was user-friendly and accessible across devices. My contributions played a key role in delivering a polished product on time.

In the Barn

Developed the app’s core features, including ad listing and product pages, and implemented Parse API for seamless data handling. Designed login and registration flow to ensure a smooth user experience. My work enhanced app functionality and usability, supporting the client’s goals of connecting livestock buyers and sellers effectively.

Mem - AI Notes

Developed an in-app note-taking editor featuring markdown, comments, links, media files, and more, making note-taking seamless and interactive for users. Created a share sheet for handling image, text, and URL sharing, enhancing app utility and user convenience. Built nearly the entire app with SwiftUI components, emphasizing a clean, modern design. My work helped the team deliver a robust and scalable application, streamlining end-user workflows.

Education

2014 - 2018

Bachelor's Degree in Software Engineering

Information Technology School - Belgrade, Serbia

Skills

Libraries/APIs

Alamofire, Firebase iOS SDK, CocoaPods, RxSwift, Lottie-iOS, Fabric

Tools

Git, Jira, Xcode, Zeplin, Crashlytics, ChatGPT, Figma

Languages

Swift, HTML, GraphQL

Frameworks

Combine, UIKit, Cocoa Touch, SwiftUI, Core Data, Core Location, MapKit, iOS SDK

Paradigms

Agile Software Development, Model View ViewModel (MVVM), VIPER Architecture, Clean Architecture, Model View Controller (MVC)

Platforms

iOS, MacOS, Firebase, Parse, Amazon Web Services (AWS)

Storage

SQLite, Firebase Realtime Database

Other

Notification Center, Push Notifications, Deep Linking, Mobile App Development, Mobile Applications, OpenAI, ChatGPT API, Location Services and Maps, Maps, Large Language Models (LLMs), Lottie, Apollo, UI Animation

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