Mateusz Pachulski – Learning Short cards on things I learned: the gap, what made it click, and how I checked it. https://pachulski.dev/learning/ 2026-11-13T00:00:00Z Mateusz Pachulski A BLE UUID says what kind of data, not which device https://pachulski.dev/learning/ble-uuid-says-what-not-which 2026-11-13T00:00:00Z In BLE, a UUID names a kind of service or characteristic and is the same on every device of that model. The device address is what tells two devices apart. A green build doesn't prove implementation() is right https://pachulski.dev/learning/gradle-api-vs-implementation 2026-11-13T00:00:00Z If a module's public API uses a type from another module, that dependency has to be api(). The modules that use it today can hide the mistake. testFixtures share fakes between modules without shipping them https://pachulski.dev/learning/gradle-test-fixtures 2026-11-13T00:00:00Z The java-test-fixtures plugin gives a module a third source set for fakes and builders. Other modules' tests can use it, and it stays out of the production jar. Objects don't run on threads. Whoever calls them does. https://pachulski.dev/learning/objects-dont-run-threads-do 2026-11-13T00:00:00Z An object doesn't belong to a thread. Its method runs on whichever thread calls it, which is why "run this on the main thread" means putting a message in the main thread's queue. Swift loses the type of a Kotlin Flow, because Flow is an interface https://pachulski.dev/learning/swift-loses-the-type-of-a-kotlin-flow 2026-11-13T00:00:00Z Kotlin/Native talks to Swift through an Objective-C header, and Objective-C only puts generics on classes. Flow is an interface, so its element type doesn't survive the trip.