Ruby objects, variables, and constants

The data for Ruby operations is mainly in parts: objects, classes, variables, constants.

Object

The basic unit of data represented in Ruby is called an object, and everything in Ruby is an object.
Common objects:

• Numeric Objects
  2, 3.14, 5 and other objects representing numbers, in addition to the matrix, complex numbers, prime numbers, formulas of the object.
• String Object
  "Hello World", "Hello" and other objects that represent text
• Array object, hash object
  A collection of multi-degree systems that represent multiple data
• Regular Expression Object
  The object of the regular expression-matching pattern
• Time Object
  For example, "January 1, 2016 13 o'clock" and other objects that represent time
• File Object
  objects that read and write to a file
• Symbol Object
  An object that identifies a label for a method, such as a name.

class

Class is the kind of object, and the attribute of an object is determined by the class.

Object	class
Numerical	Numberic
String	String
Array	Array
Hash column	Hash
Regular expressions	Regexp
File	File
Symbol	Symbol

An object of a class is an instance of a class (instance)

variables

A variable is a business card for an object. There are four types of variables in Ruby:
- Local variables (locally variable)
- Global variables (globals variable)
- instance variable (instance variable)
- class variables (classes variable)

How variables are named:

Variable Type	Naming Methods
Local variables	Start with an English letter or an underscore (_)
Global variables	Start with $
Instance variable	Start with @
class variables	Start with @@

Local variables and global variables

The valid range of local variables in a program is valid, and variable names declared somewhere in the program can also be used elsewhere. It corresponds to a global variable, and the global variable is a uniform variable anywhere in the program. Since the value of the global variable can be modified anywhere, using it in larger programs increases the complexity of the program unnecessarily, and reading programs and modifying programs can be cumbersome, hiding the fact that global variables are generally not used or used sparingly.

Constants

Constants begin with a thank-you letter, and constants can no longer be modified once they are assigned. For example, Ruby's running version (Ruby_version), run platform (ruby_platform), command line parameter array (ARGV), etc., are all predefined constants of Ruby.

Reserved Words

Reserved words cannot be used as variable names, otherwise they will be an error. Reserved words in Ruby:

Line

	ENCODING	FILE	BEGIN	END
=begin	=end	Alias	and	Begin
Defined?	Do	Else	elsif	END
Ensure	False	For	If	Inch
Module	Next	Nil	Not	Or
Redo	Rescue	Retry	Return	Self
Super	Then	True	Undef	Unless
Until	When	While	Yield

Ruby objects, variables, and constants