I wouldn't think you would have to input credit card details if you have redeemed a gift card of the proper denomination (enough value to purchase the app), as I don't have credit card details in my iTunes and I can download paid apps with a gift card.Had an old card on my itunes account that has expired.
Bought Itunes card and redeemed it, so have £20 credit.
Yet when I try to buy an app, it wants credit card details.
Am I forced into this, even though I want to use itunes credit?