IEnumerable vs Array

Entitas heavily uses arrays. Most of the api also expose this fact. Some functions return copies of the internal data structures with .ToArray() to protect the internal state from external modification which is very important.

I was wondering if I should change the whole api to IEnumerable to reduce the amount of converting to arrays. The user can call .ToArray if need otherwise we might be able to save some conversions. I haven’t checked the code and the consequences yet, but it might be a good idea.

What are your opinions? Please share below

[sschmid]

Exactly. Returning IEnumerables might keep us flexible which data structures we use and if we want to do caching or not. Returning IEnumerable prevents (not 100%) you from modifying the collection too and encourage to use copies with collection.ToArray() when you actually need to change things

[paraboxx]

Just passing in a raw IEntity[] array will lead to a lot of unnecessary copying. I once added some performance counters to find out how often I get cached results vs a fresh allocation over all groups in my game and 98% was cached results.

So I would go one step further and add an actual cache class that the user can pass in and that gets registered with the group. The group can then invalidate the caches like it does invalidate it’s internal cache with the difference that the external cache just sets a flag or something and doesn’t need to reallocate the next time it’s used. The user would be responsible for checking the flag and refreshing the cache before it’s actually used.