ruby - How to understand if unless combination in rails? -

i'm reading official rails 4 guide in section . there conditional statements don't understand . this post helps me understand cases confused following example:

def ensure_login_has_a_value     if login.nil?             self.login = email unless email.blank?    end end 

i understand in way : if login.nil? return true. code self.login = email executed, if email.blank? return true . nothing.

however when @ code :

before_create     self.name = login.capitalize if name.blank? 

i have no idea why if conditional statement there ?

when encounter kind of issue , instead of asking on stackoverflow?

with this:

before_create   self.name = login.capitalize if name.blank? end 

if this:

before_create   self.name = login.capitalize end 

then name overwritten login.capitalize. instead, want set name equal login if name isn't set. it's saying "the default value name capitalized version of login".

the first bit of code quite confusingly written , bit clumsy. rewrite thus:

def ensure_login_has_a_value   if self.login.blank? && !self.email.blank?     self.login = self.email   end end     

which think bit more readable.