Class

A Struct is a convenient way to bundle a number of attributes together, using accessor methods, without having to write an explicit class.

The Struct class generates new subclasses that hold a set of members and their values. For each member a reader and writer method is created similar to Module#attr_accessor.

Customer = Struct.new(:name, :address) do
  def greeting
    "Hello #{name}!"
  end
end

dave = Customer.new("Dave", "123 Main")
dave.name     #=> "Dave"
dave.greeting #=> "Hello Dave!"

See Struct::new for further examples of creating struct subclasses and instances.

In the method descriptions that follow, a “member” parameter refers to a struct member which is either a quoted string ("name") or a Symbol (:name).


Constants


Group

Group is a Struct that is only available when compiled with HAVE_GETGRENT.

The struct contains the following members:

name

contains the name of the group as a String.

passwd

contains the encrypted password as a String. An 'x' is returned if password access to the group is not available; an empty string is returned if no password is needed to obtain membership of the group.

Must be compiled with HAVE_STRUCT_GROUP_GR_PASSWD.

gid

contains the group's numeric ID as an integer.

mem

is an Array of Strings containing the short login names of the members of the group.

Passwd

Passwd is a Struct that contains the following members:

name

contains the short login name of the user as a String.

passwd

contains the encrypted password of the user as a String. an 'x' is returned if shadow passwords are in use. An '*' is returned if the user cannot log in using a password.

uid

contains the integer user ID (uid) of the user.

gid

contains the integer group ID (gid) of the user's primary group.

dir

contains the path to the home directory of the user as a String.

shell

contains the path to the login shell of the user as a String.

The following members below are optional, and must be compiled with special flags:

gecos

contains a longer String description of the user, such as a full name. Some Unix systems provide structured information in the gecos field, but this is system-dependent. must be compiled with HAVE_STRUCT_PASSWD_PW_GECOS

change

password change time(integer) must be compiled with HAVE_STRUCT_PASSWD_PW_CHANGE

quota

quota value(integer) must be compiled with HAVE_STRUCT_PASSWD_PW_QUOTA

age

password age(integer) must be compiled with HAVE_STRUCT_PASSWD_PW_AGE

class

user access class(string) must be compiled with HAVE_STRUCT_PASSWD_PW_CLASS

comment

comment(string) must be compiled with HAVE_STRUCT_PASSWD_PW_COMMENT

expire

account expiration time(integer) must be compiled with HAVE_STRUCT_PASSWD_PW_EXPIRE

No documentation available

Class Methods


Deserializes JSON string by constructing new Struct object with values v serialized by to_json.

The first two forms are used to create a new Struct subclass class_name that can contain a value for each member_name. This subclass can be used to create instances of the structure like any other Class.

If the class_name is omitted an anonymous structure class will be created. Otherwise, the name of this struct will appear as a constant in class Struct, so it must be unique for all Structs in the system and must start with a capital letter. Assigning a structure class to a constant also gives the class the name of the constant.

# Create a structure with a name under Struct
Struct.new("Customer", :name, :address)
#=> Struct::Customer
Struct::Customer.new("Dave", "123 Main")
#=> #<struct Struct::Customer name="Dave", address="123 Main">

# Create a structure named by its constant
Customer = Struct.new(:name, :address)
#=> Customer
Customer.new("Dave", "123 Main")
#=> #<struct Customer name="Dave", address="123 Main">

If the optional keyword_init keyword argument is set to true, .new takes keyword arguments instead of normal arguments.

Customer = Struct.new(:name, :address, keyword_init: true)
Customer.new(name: "Dave", address: "123 Main")
#=> #<struct Customer name="Dave", address="123 Main">

If a block is given it will be evaluated in the context of StructClass, passing the created class as a parameter:

Customer = Struct.new(:name, :address) do
  def greeting
    "Hello #{name}!"
  end
end
Customer.new("Dave", "123 Main").greeting  #=> "Hello Dave!"

This is the recommended way to customize a struct. Subclassing an anonymous struct creates an extra anonymous class that will never be used.

The last two forms create a new instance of a struct subclass. The number of value parameters must be less than or equal to the number of attributes defined for the structure. Unset parameters default to nil. Passing more parameters than number of attributes will raise an ArgumentError.

Customer = Struct.new(:name, :address)
Customer.new("Dave", "123 Main")
#=> #<struct Customer name="Dave", address="123 Main">
Customer["Dave"]
#=> #<struct Customer name="Dave", address=nil>

Instance Methods


Equality—Returns true if other has the same struct subclass and has equal member values (according to Object#==).

Customer = Struct.new(:name, :address, :zip)
joe   = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joejr = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
jane  = Customer.new("Jane Doe", "456 Elm, Anytown NC", 12345)
joe == joejr   #=> true
joe == jane    #=> false

Attribute Reference—Returns the value of the given struct member or the member at the given index. Raises NameError if the member does not exist and IndexError if the index is out of range.

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

joe["name"]   #=> "Joe Smith"
joe[:name]    #=> "Joe Smith"
joe[0]        #=> "Joe Smith"

Attribute Assignment—Sets the value of the given struct member or the member at the given index. Raises NameError if the member does not exist and IndexError if the index is out of range.

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

joe["name"] = "Luke"
joe[:zip]   = "90210"

joe.name   #=> "Luke"
joe.zip    #=> "90210"

Returns a hash, that will be turned into a JSON object and represent this object.

Extracts the nested value specified by the sequence of key objects by calling dig at each step, returning nil if any intermediate step is nil.

Foo = Struct.new(:a)
f = Foo.new(Foo.new({b: [1, 2, 3]}))

f.dig(:a, :a, :b, 0)    # => 1
f.dig(:b, 0)            # => nil
f.dig(:a, :a, :b, :c)   # TypeError: no implicit conversion of Symbol into Integer

Yields the value of each struct member in order. If no block is given an enumerator is returned.

Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe.each {|x| puts(x) }

Produces:

Joe Smith
123 Maple, Anytown NC
12345

Yields the name and value of each struct member in order. If no block is given an enumerator is returned.

Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe.each_pair {|name, value| puts("#{name} => #{value}") }

Produces:

name => Joe Smith
address => 123 Maple, Anytown NC
zip => 12345

Hash equality—other and struct refer to the same hash key if they have the same struct subclass and have equal member values (according to Object#eql?).

Returns a hash value based on this struct's contents.

See also Object#hash.

Returns a description of this struct as a string.

Returns the struct members as an array of symbols:

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

Yields each member value from the struct to the block and returns an Array containing the member values from the struct for which the given block returns a true value (equivalent to Enumerable#select).

Lots = Struct.new(:a, :b, :c, :d, :e, :f)
l = Lots.new(11, 22, 33, 44, 55, 66)
l.select {|v| v.even? }   #=> [22, 44, 66]

Returns the number of struct members.

Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe.length   #=> 3

Returns the values for this struct as an Array.

Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe.to_a[1]   #=> "123 Maple, Anytown NC"

Returns a Hash containing the names and values for the struct's members.

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

Stores class name (Struct) with Struct values v as a JSON string. Only named structs are supported.

Returns the struct member values for each selector as an Array. A selector may be either an Integer offset or a Range of offsets (as in Array#values_at).

Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe.values_at(0, 2)   #=> ["Joe Smith", 12345]