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