Collection radio buttons / check boxes helpers

[carlosantoniodasilva]

@rafaelfranca and I have been working to move SimpleForm's collection_radio_buttons and collection_check_boxes helpers to Rails. They work in a similar way to collecion_select, but generating a collection of radio_button/check_box + label for each item in the given collection. Here is an example usage:

collection_check_boxes :post, :author_ids, Author.all, :id, :name

It'd output something like:

<input id="post_author_ids_1" name="post[author_ids][]" type="checkbox" value="1" />
<label for="post_author_ids_1">D. Heinemeier Hansson</label>
<input id="post_author_ids_2" name="post[author_ids][]" type="checkbox" value="2" />
<label for="post_author_ids_2">D. Thomas</label>
<input name="post[author_ids][]" type="hidden" value="" />

It is possible to customize the output by giving a block to the helper. This block receives an argument, which is an "special builder" that is able to generate a label and radio_button/check_box for the given item context. For instance:

collection_check_boxes(:post, :author_ids, Author.all, :id, :name) do |b|
  b.label(:"data-value" => b.value) { b.check_box + b.text }
end

The helpers label and check_box/radio_button are available inside the block, scoped to the current element being rendered, that also accepts extra html options. The current text and value methods are also available for use, allowing better customization.

This PR also adds the ability for collection_select to receive proc values as text_method and value_method, something we've added to collection check_boxes/radio_buttons/select helpers in SimpleForm.

Thanks.

[jeremy]

/cc @josevalim

[josevalim]

@jeremy it looks good to me, let's merge?

[jeremy]

Nice job, especially with updated docs and guide.

There are a lot of other refactorings and style changes included, too, making it hard to review the code carefully.

👍 here but please do separate pulls for refactoring and style changes next time!

[carlosantoniodasilva]

@jeremy thanks, we will be paying more attention to that from now on.