Question

I am trying to write some validation logic inside of a model for one of my applications. The logic I would like to build in looks like this.

def validation
    if this == true or (!that.nil? and those < 1000)
       do something
    else
       do nothing
end

Is it possible to do this within a ruby method?

Answer 1

Sure you can. However, two things to be aware of:

• I suspect you mean this == true instead of this = true.
• Be very careful when using and and or instead of && and || – they are not equivalent. Read up on operator precedence in ruby, it’s subtly different than in other languages such as PHP. You’re probably better off sticking with && and || for most logical statements and reserving the use of or and and to control flow, such as redirect and return.

So your concrete example should probably look like this:

 if this == true || (!that.nil? && those < 1000)
   do something
 else
   do nothing
 end

In this particular case, the parentheses are redundant, since && precedes ||, but they don’t hurt, and for anything more complicated, it’s good practice to use them to avoid ambiguity and subtle bugs due to a misunderstanding of operator precedence.