Update documentation to describe ArrayChoiceList usage

[ryanotella]

For users upgrading from 2.3 to 2.7, there are a lot of deprecation warnings around ChoiceList, SimpleChoiceList and ChoiceListInterface. The recommendation is to use ArrayChoiceList instead. However, there currently isn't any documentation about how to use that, and the current 2.7 documentation suggests using the deprecated ChoiceList. See http://symfony.com/doc/current/reference/forms/types/choice.html#choice-list

This is a very complicated area of Symfony forms which has been in a bit of flux due to potential API changes, so it would be good to have some examples of usage.

I'd update the docs myself, but I haven't figured out how ArrayChoiceList actually works yet.

[xabbuh]

@ryancastle Thanks for mentioning this. However, I will close here though as we are already aware of this (see #5179). Anyway, thanks again. :)

[ryanotella]

Yeah. Fair enough. I didn't find that one.

[adamelso]

I've been looking through all the resources I can find... Symfony Docs, Symfony News posts, UPGRADE.mds, the source code, GitHub issues linked from here and others, StackOverflow, to name a few.

However, I am still not 100% certain what the upgrade course is for replacing the deprecated ObjectChoiceList with ArrayChoiceList.

As far as I can see, #5876 does not cover this issue which was meant to replace the closed #5179.

[HeahDude]

Hi @adamelso, see #6393. Hope that helps.

Cheers