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Structuring large apps ​

  • Avoid @Environment and dependency-resolvers like @Dependency - convenient yes, but:
    • they hide the dependencies
    • "everything accessible everywhere" leads to "everything accessed everywhere"
    • @Dependency and the like are mostly resolving using thread-local storage which doesn't go together with structured concurrency and its "you shouldn't concern yourself with the threads anymore"
  • Leaf view types / view types that are at the bottom of the view hierarchy only map data -> presentation - pass structs of data only
    • Action struct pattern for everything such a View cannot handle on its own
  • struct Data types only store data and offer convenience logic as long as they can do that on their own
    • data never knows where it's coming from or talks with these data sources – it can be tempting to offer convenience methods that needs to talk to data source (and wants to know or resolve them therefore) - don't.
  • Model/Repo/Coordinator objects (@Observable or plain objects) are used by outer coordinator views – here the logic happens and the parts are wired up together
    • explicit lifecycle (Who is responsible for creating this and when? (can be owned by Views or other Models or an App-wide Model)
    • Clear ownership: Who is the owner of this object?
    • get passed their dependencies to do their job via init params
      • no runtime resolving - you need to have/pass through everything needed to get the job done -> yes, this means additional code and additional refactoring work when features change - but it's easy to reason about and always trivial to write, no hidden complexity
      • create...() factory methods as clean and straightforward way to do dependency injection
    • "What does this thing need to get it's job done?" is the important question
  • All this means more boilerplate which is worth it for having a clear simple flow that's easy to follow. Code that's easy to reason about with boilerplate to enable this clarity is better than a compact but knotted ball of wool
  • Enables: Dead-simple and powerful .fixtures struct pattern for Previews and Unit Tests