Overview

At Just Eat, tracking events is a fundamental part of our business analysis and the information we collect informs our technical and strategic decisions. To collect the information required we needed a flexible, future-proof and easy to use tracking system that enables us to add, remove and swap the underlying integrations with analytical systems and services with minimal impact on our applications’ code. We also wanted to solve the problem of keeping the required event metadata up-to-date whenever the requirements change.
JustTrack is the event tracking solution we built for that and it’s available open source on Github at https://github.com/justeat/JustTrack.
Examples and documentation are available in the Github repository Readme.

Main features

• Events are declared in a .plist file and Swift 3 code is automatically generated at build time from it.
• Events can be sent to multiple destinations (called Trackers) at the same time.
• Custom Trackers are easy to create and use.

Events Definition

One of the problems we found with existing solutions is that the events are declared in code and therefore can only be maintained by developers. Similarly, existing solutions offer very generic tracking facilities for developers. Because of that, whenever the required metadata associated with an event changes for any reason, the developer has to search the code base and update all instances of the event with the correct implementation. This, of course, is a very fragile process and is prone to errors.
JustTrack solves these problems by declaring events in a plist file that is used to automatically generate equivalent definitions of the events in Swift that can be used in the app. This provides several benefits:

• Each event is uniquely identified.
• The metadata associated with each event is type checked.
• When the requirements for an event change, the developers can see it through build errors and warnings that will naturally occur.
• Plists can be edited as XML, which means anybody in the business can edit them.
• It’s easy to search for events that are no longer used and deleted events won’t compile.

An Event is made of:

• Name: the unique identifier
• Registered Trackers: List of event destinations (e.g. Google Analytics)
• Payload: The metadata associated with the event (at this time only String key-value pairs are supported)

Trackers

Another problem we found with existing solutions is that, generally speaking, all the events need to be tracked with the same Trackers. The developer doesn’t have any freedom to decide which event goes to which Tracker, and several solutions only support specific tracking technologies (such as GA, Firebase, and so on)
JustTrack solves this problem by allowing the developer to specify the “registered” trackers for each event and to create custom trackers.
A Tracker is an object implementing the JETracker protocol and is loaded using: tracker.loadCustomTracker( ... ) function. You can implement any tracker you want and JustTrack provides a few default trackers:

• JETrackerConsole – print events to the system’s console
• JEFacebookTraker (not yet implemented)
• JEGoogleAnalyticsTraker (not yet implemented, Google’s pods can’t be used as a dependency in a pod)
• JETrakerFirebase (not yet implemented, Google’s pods can’t be used as a dependency in a pod)

Conclusions

Using JustTrack you can easily track your app’s events to multiple destinations, having all the necessaire flexibility, intrinsic events documentation and all the expandability you will ever need in future, all of that writing the minimum amount of code possible.

About the author

Federico Cappelli is a Senior iOS Engineer and iOS COG Leader at Just Eat.