Ruby Mistakes

ruby_mistakes.rb

Dont misuse predicate methods:
-------
  predicate methods used to return either true or false.  they ends with "?"

It’s been a while since we’ve rolled out our previous article about the most common Rails mistakes that beginner developers usually make. In this regard, we aren’t going to bother you with too much of introduction and get straight to the point. This article will be dedicated to the standard approaches to Ruby development which are also called “the Ruby way”. As usual, the most critical mistakes are highlighted with RED. So, let’s find out what exactly newbies do wrong/forget to do or don’t do at all.
They misuse predicates

A predicate is a method that answers a specific question and always returns either “yes” or “no”. It’s not supposed to affect any other piece of code or perform any additional actions. According to the Ruby on Rails style guides, predicates are followed by a question mark at the end of the method name.
############
## WRONG ##
############

def author?
  if current_user.id ==  course.user.id
    current_user.add_role(‘author’)
  end
end

def has_any_courses?
  current_user.courses.count
end
  
##############
##  RIGHT   ##
##############

current_user.add_role(‘author’) if author?

def author?
  current_user.id == course.user.id
end

def has_any_courses?
  current_user.courses.size > 0
end

use present nil , blank  meaningfully:
----------------------
  
############
## WRONG  ##
############

if course
  render '...'
end

raise NotAuthorized unless auth_token
  
##############
##  RIGHT   ##
##############

if course.present?
  render '...'
end
  
raise NotAuthorized unless auth_token.present?

Use "||" when required:
-----------------------------
  instance variable is considered “nil” if it’s not declared. 
With that in mind, you can leverage memoization.
 Using the first option in the code sample below will perform four requests
: two for the user selection, one for the articles selection, and one for the courses selection. 
  However, if you look at the second option, 
  you will see that the number of requests is now down to three: 
  one for the user selection, one for the articles selection, 
    and one for the courses selection.
        
      ############
## WRONG  ##
############

def user
  User.find(params[:id})
end

user.articles
user.courses
  
##############
##  RIGHT   ##
##############
 
def user
  @user ||= User.find(params[:id})
end

user.articles
user.courses
    
    Use single quotes when necessory:
    ------------------------
      
############
## WRONG  ##
############

render ‘new’
social_network = “facebook”
message = “Can’t do this”

##############
##  RIGHT   ##
##############

render :new
social_network = ‘facebook’
message = “Can’t do this”
    
    Use of  constants:
    ---------
      when checking in a common value , then use CONSTANTS
        like
        PI = 3.14
         the value of the PI is always 3.14. so dont need to add the value as 3.14
        always use constants with meaning full words.
          
  always use multiple conditions as methods:
        --------------
          ############
## WRONG  ##
############

if course.courses_users.where(ban: true).exists?(user_id: id)
  if course.user_id ==   id
    if #something                                                                                                                                                                                                          course.part.exists?(self)
    end
  end
end

##############
##  RIGHT   ##
##############

if part_in?(course) && banned?(course) && author?(course)
  # do something
end

def part_in?(course)
  course.part.exists?(self)
end

def banned?(course)
  course.courses_users.where(ban: true).exists?(user_id: id)
end

def author?(course)
course.user_id == id
end
        
       limit the use of case and if 
         -----------------------------
         ############
## WRONG  ##
############

def somethod(name)
  case name
  when ‘a’
    ‘A’
  when ‘b’
    ‘B’
  when '…'
    '...'
  end
end  

##############
##  RIGHT   ##
##############

CASES = {
  ‘a’ => ‘A’,
  ‘b’ => ‘B’,
}
  
def somethod(name)
  CASES[name]
end

# or you could go with this option:

def somethod(name)
  send(:”process_#{name}”)
end

def process_a
  ‘A’
end

def process_b
  ‘B’
end