Conclusion

Associated types are a powerful concept however they come with a fair share of difficulties. Most notably, as soon as you introduce an associated type you can't use it like you'd use normal full types. This article provided several patterns that make it a bit easier to handle associated type problems in your codebase. Each of these patterns has downsides though. In general, if you intend to use associated types in a protocol, one of the best solutions is to try to only use the types that implement this protocol instead of the protocol itself. Because then you don't even need those patterns.