"Red State" director Smith, who has worked with Affleck on six feature films, discovered the extent of the new Batman star's love for the character when he purchased his old home, reported Digital Spy.
"His house that I would end up buying, when I first saw it he was touring me through the place and said, 'Come here, I gotta show you my room'.
"He brings me into the room and goes, 'Look at this'. There's an office room and this beautiful bookcase - he reached under and he clicked something and all of a sudden the bookcase opened. I was like, 'No! You built a Batcave?. And he was like, 'No I built a Batcave entrance!' When you went in behind the bookcase it was a panic room," he said.
"This dude has loved Batman going as far back as I can remember. He only did Daredevil because he loved Frank Miller's Dark Knight Returns," Smith explained.
"He's like, 'They're never going to make another Batman', because this was after Batman had nipples. So he was like, 'Daredevil's cool, and Miller wrote him as well'. So he liked the character, but it was always rooted in Batman. He's always been into the notion. He'll honour the character. I honestly think the dude's a great actor, it makes absolute sense," he added.