Ruby逻辑和/或链

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.

Answer 2

Sure, i would only recommend you to create smaller methods like a method compare each of the attributes and on that method call them.

def validation
  if this? or others?
    #do something
  else
    #do nothing
  end
end

private

def others?
  that? and those?
end

def this?
  this == true
end

def that?
  that != nil
end

def those?
  those < 1000
end