variables in Ruby on Rails

Question

What s the difference between  title and title  Since both of them can be variable names  Also  how do I decide which kind of variable I should use  With   or not

User · Accepted Answer

title is a local variable  They only exists within its scope  current block    title is an instance variable - and is available to all methods within the class   You can read more here  http   strugglingwithruby blogspot dk 2010 03 variables html  In Ruby on Rails - declaring your variables in your controller as instance variables   title  makes them available to your view

User · Answer

variables are called instance variables in ruby  Which means you can access these variables in ANY METHOD  inside the class   Across all methods in the class   Variables without the   symbol are called local variables  which means you can access these local variables within THAT DECLARED METHOD  only  Limited to the local scope   Example of  Instance Variables   class Customer   def initialize id  name  addr       cust id   id      cust name   name      cust addr   addr   end    def display details     puts  Customer id    cust id       puts  Customer name    cust name       puts  Customer address    cust addr     end end   In the above example  cust id   cust name   cust addr are accessed in another method within the class  But the same thing would not be accessible  with local variables

User · Answer

Use  title in your controllers when you want your variable to be available in your views  The explanation is that  title is an instance variable while title is a local variable  Rails makes instance variables from controllers available to views because the template code  erb  haml  etc  is executed within the scope of the current controller instance

User · Answer

A local variable is only accessible from within the block of it s initialization  Also a local variable begins with a lower case letter  a-z  or underscore        And instance variable is an instance of self and begins with a   Also an instance variable belongs to the object itself  Instance variables are the ones that you perform methods on i e   send etc  example    user   User all   The  user is the instance variable  And Uninitialized instance variables have a value of Nil

User · Answer

The difference is in the scope of the variable  The  version is available to all methods of the class instance   The short answer  if you re in the controller and you need to make the variable available to the view then use  variable   For a much longer answer try this  http   www ruby-doc org docs ProgrammingRuby html tut classes html

User · Answer

A tutorial about What is Variable Scope  presents some details quite well  just enclose the related here      ------------------ ----------------------    Name Begins With      Variable Scope       ------------------ ----------------------                       A global variable                           An instance variable      a-z  or           A local variable          A-Z               A constant                                  A class variable        ------------------ ----------------------

User · Answer

variables are instance variables  without are local variables   Read more at http   ruby about com od variables a Instance-Variables htm

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