Ruby | Struct Class

Struct is a compact way to group together a number of attributes, using accessor methods, without creating an explicit class. The Struct class is a creator of specific classes, each one is defined to hold a set of variable and their accessors. The subclass of Struct class is Struct::Tms.

Example:

# Ruby program to illustrate
# use of Struct

# creating Struct
# Geek is generated class
Geek = Struct.new(:tut_name, :cate_name) do

def gfg

    "This is #{cate_name} class tutorial in #{tut_name}."

  end
end

# creating object of struct
a = Geek.new("Ruby", "Struct")
puts a.gfg

Output:

This is Struct class tutorial in Ruby.

Class Method

new : This method creates a new class named by string, consisting accessor methods for the given symbols. If the name string is omitted, then the anonymous structure class will be created. Otherwise, the name of this struct will appear as a constant in Struct class, so the name must be unique from all the Structs in the system and should start with capital letters. When a structured class is assigned to the constant, it effectively gives the class the name of the constant.

Struct.new([string][, symbol])
Struct.new([string][, symbol]){block}

Example:

# Ruby program to illustrate
# creating structure

# Creating a structure with a name in struct
Struct.new("Geek", :tutorial_name, :topic_name)
Struct::Geek.new("ruby", "Struct")

# Create a structure named by its constant
Geek = Struct.new(:tutorial_name, :topic_name)
p Geek.new("Ruby", "Struct")

Output:

#<struct Geek tutorial_name="Ruby", topic_name="Struct">

Struct.new class return a new class object, which is used to create a specific instance of the new structure. In this instance, the actual parameter is less than or equal to the number of attributes defined for this class. The default value of unset parameters is nil. Passing of too many parameters will raise an ArgumentError exception.

Geek.new([obj])

Example:

# Ruby program to illustrate
# creating objects of structure

# Create structure
Geek = Struct.new(:tutorial_name, :topic_name)

# Creating objects
str = Geek.new("Ruby", "Struct")
p str.tutorial_name
p str.topic_name

Output:

"Ruby"
"Struct"

Instance Method

1. == : It is known as Equality. It returns true if str is equal to other_struct in terms of the values of instance variables. And also they must be of same class as created by Struct.new. Otherwise, it return false.

   str == other_struct

   Example:

   # Ruby program to illustrate
   # check equality
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   other_struct = Geek.new("Java", "array")
   str1 = Geek.new("Ruby", "Struct")
   
   # Check equality
   p str == other_struct
   p str == str1

   Output:

   false
   true
   

2. [] : It is known as Attribute Reference. It returns the value of the instance variable named by symbol or index(0..length-1) by int. If the named variable does not exist, then it raises NameError and if the index is out of range then it raises IndexError.

   str[symbol] 
   str[int]
   

   Example:

   # Ruby program to illustrate
   # use of []
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   
   # Using []
   p str[:tutorial_name]
   p str["topic_name"]

   Output:

   "Ruby"
   "Struct"
   

3. []= : It is known as Attribute Assignment. It is used to assign the instance variable name with a symbol or the value of obj by int and return it. If the name of the instance variable does not exist or if the index is out of range, then it raise NameError.

   str[symbol] = obj
   str[int] = obj
   

   Example:

   # Ruby program to illustrate
   # use of []=
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   
   # Using []=
   str[:tutorial_name]= "Java"
   str[:topic_name]= "array"
   p str.tutorial_name
   p str.topic_name

   Output:

   "Java"
   "array"
   

4. each : This method call block for each instance variable and pass the value as a parameter.

   str.each_pair{|obj| block}

   Example:

   # Ruby program to illustrate
   # use of each method
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   
   # Using each method
   str.each{|a| puts (a)}

   Output:

   Ruby
   Struct
   

5. each_pair : This method calls block for each instance variable and pass the name and value as parameter.

   str.each_pair{|symbol, obj| block}

   Example:

   # Ruby program to illustrate
   # use of each_pair method
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   
   # Using each_pair  method
   str.each_pair{|tutorial_name, a| puts ("#{tutorial_name} => #{a}")}

   Output:

   tutorial_name => Ruby
   topic_name => Struct
   

6. length : This method returns the number of instance variables. The return type of this method is an integer.

   str.length

   Example:

   # Ruby program to illustrate
   # use of length method
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   
   # Using the length method
   p str.length

   Output:

   2
   

7. members : This method returns an array of string that represent the name of the instance variable.

   str.members

   Example:

   # Ruby program to illustrate
   # use of members
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   
   
   # Using members method
   p str.members

   Output:

   [:tutorial_name, :topic_name]
   

8. size : This method is similar to Struct#length method. The return type of this method is an integer.

   str.size

9. to_a : This method returns the values for this instance as an array.

   str.to_a

   Example:

   # Ruby program to illustrate
   # use of to_a method
   
   # Create structure
   Geek = Struct.new(:tutorial_name, :topic_name)
   
   # Creating objects
   str = Geek.new("Ruby", "Struct")
   
   # Using to_a method
   p str.to_a[0]
   p str.to_a[1]

   Output:

   "Ruby"
   "Struct"
   

10. values : This method is similar to Struct#to_a method.

    str.values

11. values_at : This method return an array that consist the element in str corresponding to the given indices. The selectors may be integer indices or range.

    str.values_at([selector])

    Example:

    # Ruby program to illustrate
    # use of value_at method
    
    # Create structure
    Geek = Struct.new(:p, :q, :r, :s)
    
    # Creating objects
    str = Geek.new(12, 13, 14, 15)
    
    # Using values_at method
    p str.values_at(2, 1)
    p str.values_at(2, 1, 0, 3)

    Output:

    Geek
    [14, 13]
    [14, 13, 12, 15]
    

Reference: https://ruby-doc.org/core-2.2.0/Struct.html