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

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"
```
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\""
```
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"
```
<=> :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
```
== : 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
```
[] : This method returns the value of sym.to_s[].
```
sym[idx] --> char 
sym[b, n] --> string
```
capitalize : This method is similar to Symbol#to_s.
```
sym.capitalize
```

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

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"
```
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
```
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"
```
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"
```
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"
```
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"]
```
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
```