Does the だ get dropped after an い-adjective


I was told how an older non-native lady would say "it's okay!" and that it was
perceived to be just like that person and cute many because it was
grammatically incorrect. She would say, いいだよ

Now I didn't know that rule but I was sure I had heard いいだよ before. It is such
a simple statement but even these things trip me up.

So I'm guessing the rule is like

[code]

    だ after な-adjectives, nouns
    No だ after い-adjectives 
    
[/code]

Can I get something definitive on this please? What about adverbs?




Are you sure it's wasn't いいんだよ and you just couldn't hear the ん clearly?




There are regions where "いいだよ" gets said
(http://www.geocities.co.jp/Technopolis/1775/mikawa.html), but it's not
standard 標準語 Japanese. With adverbs, it probably depends. I don't think you
could say "すぐにだ”, but "ときどきだ" sounds OK.

