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Rails - Basic Steps III

pValidations

  • Validations are a type of ActiveRecord
  • Validations are defined in our models

Implement Validations

  1. Go to  root_app/app/models
  2. Open files *.rb for each model

Mandatory field

    • validates_presence_of  :field
    • Ex:  validates_presence_of  :title

Classes

  • The basic syntax is
class MyClass
       @global_variable
       
       def my_method
             @method_variable
       end
end

  • Create an instance
    • myInstance = MyClass.new
  • Invoke a mehod
    • mc.my_method
  • class() method returns the type of the object
  • In Ruby, last character of method define the behavior
    • If ends with a question -> return a boolean value
    • If ends with an exclamation -> change the state of the object

Getter / Setter method

def global_variable
      return @global_variable
end
def global_variable=(val)
       @global_variable  = val
end

  • Other way is used the word attr_accessor
    • Ex:    attr_accessor  :global_variable  
    • Ex2:  attr_accessor  :global_variable, :second_variable  
  • If you only want a setter use: attr_write
  • If you only want a getter use: attr_reader

  • return is not necessary, the last line executed is what is returned.
  • Even though return you can use return
  • Class methods are created with the reserved word self after a point (.)
    • To call the method:  MyClass.class_method
class MyClass
       @global_variable
       
       def self.class_method
             @method_variable
       end
end

Inhearence

  • Use the symbol <
    • Ex:   class NewClass < Superclass

Modules

  • Use the word module to create a module with his own namespace
  • To include a module use the word require
    • require'module_X'

Assignments

  • All the assignments are by references not by value
  • Ruby, support parallel assignemt
    • Ex: a, b = b, a 

Variables

  • name - could be a local variable
  • @name - instance variable
  • @@name - class variable  (static variable)
  • $Name - global variable
  • The convention is use underscores for variables
  • The convention is use camel case for classes

Strings

  • All the content between double quotes
  • If you put #{} inside a string, Ruby interprets as code
  • If you use `` the interprets as a command
  • Symbol is when use this symbol : 
  • A Symbol is used when you don´t want to manipulate the characters

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