やりかた1
options_for_select([
['item 1', '1'],
['item 2', '2'],
['item 3', '3'],
['item 4', '4'],
], disabled: [1, 4])
やりかた2
これでもいける
options_for_select([
['item 1', '1', disable: true],
['item 2', '2', disable: false],
['item 3', '3', disable: false],
['item 4', '4', disable: true],
])
See also ActionView::Helpers::FormOptionsHelper#options_for_select
いろんな書き方がありすぎる…
付録
一括で disabled
にするのはこれで
options_for_select(items, disabled: true)