I'm quite new to Rails and found a little snippet to validate presence and uniqueness step by step: first check presence, then check uniqueness. validates :email, :presence => true, :allow_blank => true, :uniqueness => { :case_sensitive => false } I'm a little bit confused about using presence => true and allow_blank => true together. Without using allow_blank => true both rules will be checked at
![Understanding Rails validation: what does allow_blank do?](https://cdn-ak-scissors.b.st-hatena.com/image/square/98d6f053a97a87156775f60757c60865d0f2c47d/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Fstackoverflow%2FImg%2Fapple-touch-icon%402.png%3Fv%3D73d79a89bded)