Itterating in [Text]

I am trying to itterate in an array of Text using the below function, but I receive an error. Not sure what I am doing wrong:

func addVideo2Album_(albums : ?[Text], videoId : VideoId) : ?() {
	do ? {
		switch(albums) {
			case null {
			case (?_) {
				for (alb in albums.vals()){

it gives me this error refering the line for (…):

Expected object type but expression produced type ?[Text]

oops! Silly mistake when handling optional type. just needed to change ?_ to ?albs and replace alums.vals() with albs.vals()