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Ruby | Symbol Class

  • Last Updated : 11 Oct, 2019

The objects of the Symbol class represent the names present inside the Ruby interpreter. They are usually generated by using :name literal syntax or by using to_sym methods. The similar Symbol objects are created for a given name string for the duration of a program’s execution, regardless of the content and meaning of the name.

Example:




# Ruby program to illustrate 
# Symbol objects
  
# context 3
module Geeks1
  
class Max
end
$a1 = :Max
end
  
# context 1
module Geeks2
  
Max = 1
$a2 = :Max
end
  
# context 2
def Max()
  
end
  
$a3 = :Max
  
puts $a1.object_id 
puts $a2.object_id 
puts $a3.object_id 

Output:

1675428
1675428
1675428

Explanation: If Max is a constant in context1, a method in context2, or class in the context3, then this :Max will be the same object in all given contexts.

Class Method

all_symbols : This method returns an array of symbols that currently present in the Ruby’s symbol table.



Symbol.all_symbols

Example:




# Ruby program to illustrate 
# the use of all_symbol method
  
# Using all_symbol method
puts Symbol.all_symbols.size 
puts Symbol.all_symbols[1, 20]

Output:

3250
"
#
$
%
&
'
(
)
*
+
,
-
.
/
:
;
<
=
>
?

Instance Methods

  1. id2name : This method returns a string that is representation of sym.
    sym.id2name

    Example:




    # Ruby program to illustrate 
    # the use of id2name method
      
    # Using id2name method
    p :Geeks.id2name 
    p :"Welcome to GeeksforGeeks Portal".id2name

    Output:

    "Geeks"
    "Welcome to GeeksforGeeks Portal"
    
  2. inspect : This method return the representation of sym in the form of symbol literal.
    sym.inspect

    Example:




    # Ruby program to illustrate 
    # the use of inspect method
      
    # Using inspect method
    p :geeks.inspect
    p :"welcome to geeksforgeeks portal".inspect

    Output:

    ":geeks"
    ":\"welcome to geeksforgeeks portal\""
    
  3. to_s : This method is similar to Symbol#id2name. This method returns the name or a string that corresponding to sym.
    sym.to_s

    Example:




    # Ruby program to illustrate 
    # the use of to_s method
      
    # Using to_s method
    p :geeks.to_s
    p :"welcome to geeksforgeeks portal".to_s

    Output:



    "geeks"
    "welcome to geeksforgeeks portal"
    
  4. <=> :It compares sym to other_sym after calling to_s. It returns -1 if sym is less than other_sym, it returns 0 if sym is equal to other_sym, or it returns +1 if sym is greater than other_sym.
    sym <=> other_sym 

    Example:




    # Ruby program to illustrate 
    # use of <=>
      
    # Using <=>
    a= :geeks
    b = :"welcome to geeksforgeeks portal"
    puts a<=>b
    c= :geeks
    puts a<=>c
    puts b<=>a

    Output:

    -1
    0
    1
    
  5. == : It returns true if the sym is equal to obj, otherwise it return false.
    sym== obj

    Example:




    # Ruby program to illustrate 
    # use of ==
      
    # Using ==
    a= :geeks
    b = :"welcome to geeksforgeeks portal"
    puts a==b
    c= :geeks
    puts a==c

    Output:

    false
    true
    
  6. [] : This method returns the value of sym.to_s[].
    sym[idx] --> char 
    sym[b, n] --> string
    
  7. capitalize : This method is similar to Symbol#to_s.
    sym.capitalize
  8. casecmp : This method is case-insensitive version of symbol <=$gt;. It will return -1, 0, 1, or nil. It is worked on A-Z/a-z, not on all Unicode. In this method nil is returned when the two symbols have incompatible encodings or if other_sym is not a symbol.
    sym.casecmp(other)

    Example:




    # Ruby program to illustrate 
    # use of casecmp method
      
    # Using casecmp method
    puts :GeeKs.casecmp(:geeks)
    puts :GeeKsGfg.casecmp(:geeksG)
    puts :GeeKsGfg.casecmp(:geeksGfgz)
    puts :GeeKsGfg.casecmp(3)

    Output:

    0
    1
    -1
    nil
  9. downcase : This method converts upper-case letters in lower-case.
    sym.downcase

    Example:




    # Ruby program to illustrate 
    # use of the downcase method
      
    # Using the downcase method
    puts :"WELCOME TO GEEKSFORGEEKS".downcase

    Output:

    :"welcome to geeksforgeeks"
  10. length : This method returns the length of the given sym.
    sym.length

    Example:




    # Ruby program to illustrate 
    # use of length method
      
    # Using length method
    puts :GeeKsGfg.length

    Output:



    8
  11. slice : This method is similar to Symbol#to_s. This method provides you character on the given index from the sym .
    sym.slice(index)
    sym.slice(b, n)
    

    Example:




    # Ruby program to illustrate 
    # use of slice method
      
    # Using slice method
    p :GeeKsGfg.slice(3)
    p :GeeKsGfg.slice(6)

    Output:

    "K"
    "f"
    
  12. swapcase : This method interchange the case of the characters that present in sym. In other words, it converts lower-case into upper-case and upper-case into lower-case.
    sym.swapcase

    Example:




    # Ruby program to illustrate 
    # use of the swapcase method
      
    # Using swapcase method
    p "WELcome TO geeksFORGEEKS".swapcase

    Output:

    "welCOME to GEEKSforgeeks"
  13. upcase : This method converts lower-case characters into upper-case.
    sym.upcase

    Example:




    # Ruby program to illustrate 
    # use of the upcase method
      
    # Using upcase method
    p "welcome to geeksforgeeks".upcase

    Output:

    "WELCOME TO GEEKSFORGEEKS"
  14. to_proc : This method return a Proc object which answer to the given method by sym.
    sym.to_proc

    Example:




    # Ruby program to illustrate 
    # use of to_proc method
      
    # Using to_proc method
    p (1..5).collect(&:to_s)

    Output:

     ["1", "2", "3", "4", "5"]
  15. to_sym This method returns a symbol that corresponding to an object. Here sym has been already a symbol, so in this case it returns it.
    sym.to_sym

Reference: https://ruby-doc.org/core-2.5.0/Symbol.html#method-i-5B-5D




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