Struct

Class Struct provides a convenient way to create a simple class that can store and fetch values.

This example creates a subclass of Struct, Struct::Customer; the first argument, a string, is the name of the subclass; the other arguments, symbols, determine the members of the new subclass.

Customer = Struct.new('Customer', :name, :address, :zip)
Customer.name       # => "Struct::Customer"
Customer.class      # => Class
Customer.superclass # => Struct

Corresponding to each member are two methods, a writer and a reader, that store and fetch values:

methods = Customer.instance_methods false
methods # => [:zip, :address=, :zip=, :address, :name, :name=]

An instance of the subclass may be created, and its members assigned values, via method ::new:

joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe # => #<struct Struct::Customer name="Joe Smith", address="123 Maple, Anytown NC", zip=12345>

The member values may be managed thus:

joe.name    # => "Joe Smith"
joe.name = 'Joseph Smith'
joe.name    # => "Joseph Smith"

And thus; note that member name may be expressed as either a string or a symbol:

joe[:name]  # => "Joseph Smith"
joe[:name] = 'Joseph Smith, Jr.'
joe['name'] # => "Joseph Smith, Jr."

See Struct::new.

What’s Here

First, what’s elsewhere. Class Struct:

• Inherits from class Object.

• Includes module Enumerable, which provides dozens of additional methods.

Here, class Struct provides methods that are useful for:

• Creating a Struct Subclass

• Querying

• Comparing

• Fetching

• Assigning

• Iterating

• Converting

Methods for Creating a Struct Subclass

::new

Returns a new subclass of Struct.

Methods for Querying

hash

Returns the integer hash code.

length, size

Returns the number of members.

Methods for Comparing

#==

Returns whether a given object is equal to self, using == to compare member values.

eql?

Returns whether a given object is equal to self, using eql? to compare member values.

Methods for Fetching

[]

Returns the value associated with a given member name.

to_a, values, deconstruct

Returns the member values in self as an array.

deconstruct_keys

Returns a hash of the name/value pairs for given member names.

dig

Returns the object in nested objects that is specified by a given member name and additional arguments.

members

Returns an array of the member names.

select, filter

Returns an array of member values from self, as selected by the given block.

values_at

Returns an array containing values for given member names.

Methods for Assigning

[]=

Assigns a given value to a given member name.

Methods for Iterating

each

Calls a given block with each member name.

each_pair

Calls a given block with each member name/value pair.

Methods for Converting

inspect, to_s

Returns a string representation of self.

to_h

Returns a hash of the member name/value pairs in self.