Ruby | Symbol Class

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