Struct

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

Passwd

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

Group

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.

Tms

An obsolete name of Process::Tms for backward compatibility

Class Methods

json_create(object)

ext/json/lib/json/add/struct.rb View on GitHub

          
            # File tmp/rubies/ruby-2.6.10/ext/json/lib/json/add/struct.rb, line 10
def self.json_create(object)
  new(*object['v'])
end

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

Struct.new([class_name] [, member_name]+) → StructClass

Struct.new([class_name] [, member_name]+, keyword_init: true) → StructClass

Struct.new([class_name] [, member_name]+) {|StructClass| block } → StructClass

StructClass.new(value, ...) → object

StructClass[value, ...] → object

struct.c View on GitHub

          
            static VALUE
rb_struct_s_def(int argc, VALUE *argv, VALUE klass)
{
    VALUE name, rest, keyword_init = Qfalse;
    long i;
    VALUE st;
    st_table *tbl;

    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    name = argv[0];
    if (SYMBOL_P(name)) {
        name = Qnil;
    }
    else {
        --argc;
        ++argv;
    }

    if (RB_TYPE_P(argv[argc-1], T_HASH)) {
        static ID keyword_ids[1];

        if (!keyword_ids[0]) {
            keyword_ids[0] = rb_intern("keyword_init");
        }
        rb_get_kwargs(argv[argc-1], keyword_ids, 0, 1, &keyword_init);
        if (keyword_init == Qundef) {
            keyword_init = Qfalse;
        }
        --argc;
    }

    rest = rb_ident_hash_new();
    RBASIC_CLEAR_CLASS(rest);
    tbl = RHASH_TBL(rest);
    for (i=0; i<argc; i++) {
        VALUE mem = rb_to_symbol(argv[i]);
        if (st_insert(tbl, mem, Qtrue)) {
            rb_raise(rb_eArgError, "duplicate member: %"PRIsVALUE, mem);
        }
    }
    rest = rb_hash_keys(rest);
    st_clear(tbl);
    RBASIC_CLEAR_CLASS(rest);
    OBJ_FREEZE_RAW(rest);
    if (NIL_P(name)) {
        st = anonymous_struct(klass);
    }
    else {
        st = new_struct(name, klass);
    }
    setup_struct(st, rest);
    rb_ivar_set(st, id_keyword_init, keyword_init);
    if (rb_block_given_p()) {
        rb_mod_module_eval(0, 0, st);
    }

    return st;
}

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

struct == other → true or false

struct.c View on GitHub

          
            static VALUE
rb_struct_equal(VALUE s, VALUE s2)
{
    if (s == s2) return Qtrue;
    if (!RB_TYPE_P(s2, T_STRUCT)) return Qfalse;
    if (rb_obj_class(s) != rb_obj_class(s2)) return Qfalse;
    if (RSTRUCT_LEN(s) != RSTRUCT_LEN(s2)) {
        rb_bug("inconsistent struct"); /* should never happen */
    }

    return rb_exec_recursive_paired(recursive_equal, s, s2, s2);
}

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

struct[member] → object

struct[index] → object

struct.c View on GitHub

          
            VALUE
rb_struct_aref(VALUE s, VALUE idx)
{
    int i = rb_struct_pos(s, &idx);
    if (i < 0) invalid_struct_pos(s, idx);
    return RSTRUCT_GET(s, i);
}

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"

struct[member] = obj → obj

struct[index] = obj → obj

struct.c View on GitHub

          
            VALUE
rb_struct_aset(VALUE s, VALUE idx, VALUE val)
{
    int i = rb_struct_pos(s, &idx);
    if (i < 0) invalid_struct_pos(s, idx);
    rb_struct_modify(s);
    RSTRUCT_SET(s, i, val);
    return val;
}

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"

as_json(*)

ext/json/lib/json/add/struct.rb View on GitHub

          
            # File tmp/rubies/ruby-2.6.10/ext/json/lib/json/add/struct.rb, line 16
def as_json(*)
  klass = self.class.name
  klass.to_s.empty? and raise JSON::JSONError, "Only named structs are supported!"
  {
    JSON.create_id => klass,
    'v'            => values,
  }
end

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

struct.dig(key, ...) → object

struct.c View on GitHub

          
            static VALUE
rb_struct_dig(int argc, VALUE *argv, VALUE self)
{
    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    self = rb_struct_lookup(self, *argv);
    if (!--argc) return self;
    ++argv;
    return rb_obj_dig(argc, argv, self, Qnil);
}

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

struct.each {|obj| block } → struct

struct.each → enumerator

struct.c View on GitHub

          
            static VALUE
rb_struct_each(VALUE s)
{
    long i;

    RETURN_SIZED_ENUMERATOR(s, 0, 0, struct_enum_size);
    for (i=0; i<RSTRUCT_LEN(s); i++) {
        rb_yield(RSTRUCT_GET(s, i));
    }
    return s;
}

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

struct.each_pair {|sym, obj| block } → struct

struct.each_pair → enumerator

struct.c View on GitHub

          
            static VALUE
rb_struct_each_pair(VALUE s)
{
    VALUE members;
    long i;

    RETURN_SIZED_ENUMERATOR(s, 0, 0, struct_enum_size);
    members = rb_struct_members(s);
    if (rb_block_arity() > 1) {
        for (i=0; i<RSTRUCT_LEN(s); i++) {
            VALUE key = rb_ary_entry(members, i);
            VALUE value = RSTRUCT_GET(s, i);
            rb_yield_values(2, key, value);
        }
    }
    else {
        for (i=0; i<RSTRUCT_LEN(s); i++) {
            VALUE key = rb_ary_entry(members, i);
            VALUE value = RSTRUCT_GET(s, i);
            rb_yield(rb_assoc_new(key, value));
        }
    }
    return s;
}

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

struct.eql?(other) → true or false

struct.c View on GitHub

          
            static VALUE
rb_struct_eql(VALUE s, VALUE s2)
{
    if (s == s2) return Qtrue;
    if (!RB_TYPE_P(s2, T_STRUCT)) return Qfalse;
    if (rb_obj_class(s) != rb_obj_class(s2)) return Qfalse;
    if (RSTRUCT_LEN(s) != RSTRUCT_LEN(s2)) {
        rb_bug("inconsistent struct"); /* should never happen */
    }

    return rb_exec_recursive_paired(recursive_eql, s, s2, s2);
}

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?).

struct.filter {|obj| block } → array

struct.filter → enumerator

struct.c View on GitHub

An alias for select

struct.hash → integer

struct.c View on GitHub

          
            static VALUE
rb_struct_hash(VALUE s)
{
    long i, len;
    st_index_t h;
    VALUE n;

    h = rb_hash_start(rb_hash(rb_obj_class(s)));
    len = RSTRUCT_LEN(s);
    for (i = 0; i < len; i++) {
        n = rb_hash(RSTRUCT_GET(s, i));
        h = rb_hash_uint(h, NUM2LONG(n));
    }
    h = rb_hash_end(h);
    return INT2FIX(h);
}

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

struct.inspect → string

struct.c View on GitHub

          
            static VALUE
rb_struct_inspect(VALUE s)
{
    return rb_exec_recursive(inspect_struct, s, 0);
}

Returns a description of this struct as a string.

struct.length → integer

struct.c View on GitHub

An alias for size

struct.members → array

struct.c View on GitHub

          
            static VALUE
rb_struct_members_m(VALUE obj)
{
    return rb_struct_s_members_m(rb_obj_class(obj));
}

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]

struct.select {|obj| block } → array

struct.select → enumerator

struct.c View on GitHub

          
            static VALUE
rb_struct_select(int argc, VALUE *argv, VALUE s)
{
    VALUE result;
    long i;

    rb_check_arity(argc, 0, 0);
    RETURN_SIZED_ENUMERATOR(s, 0, 0, struct_enum_size);
    result = rb_ary_new();
    for (i = 0; i < RSTRUCT_LEN(s); i++) {
        if (RTEST(rb_yield(RSTRUCT_GET(s, i)))) {
            rb_ary_push(result, RSTRUCT_GET(s, i));
        }
    }

    return result;
}

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]

Struct#filter is an alias for Struct#select.

struct.size → integer

struct.c View on GitHub

          
            VALUE
rb_struct_size(VALUE s)
{
    return LONG2FIX(RSTRUCT_LEN(s));
}

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

struct.to_a → array

struct.c View on GitHub

          
            static VALUE
rb_struct_to_a(VALUE s)
{
    return rb_ary_new4(RSTRUCT_LEN(s), RSTRUCT_CONST_PTR(s));
}

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"

struct.to_h → hash

struct.to_h {|name, value| block } → hash

struct.c View on GitHub

          
            static VALUE
rb_struct_to_h(VALUE s)
{
    VALUE h = rb_hash_new_with_size(RSTRUCT_LEN(s));
    VALUE members = rb_struct_members(s);
    long i;
    int block_given = rb_block_given_p();

    for (i=0; i<RSTRUCT_LEN(s); i++) {
        VALUE k = rb_ary_entry(members, i), v = RSTRUCT_GET(s, i);
        if (block_given)
            rb_hash_set_pair(h, rb_yield_values(2, k, v));
        else
            rb_hash_aset(h, k, v);
    }
    return h;
}

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

If a block is given, the results of the block on each pair of the receiver will be used as pairs.

Customer = Struct.new(:name, :address, :zip)
joe = Customer.new("Joe Smith", "123 Maple, Anytown NC", 12345)
joe.to_h[:address]   #=> "123 Maple, Anytown NC"
joe.to_h{|name, value| [name.upcase, value.to_s.upcase]}[:ADDRESS]
                     #=> "123 MAPLE, ANYTOWN NC"

to_json(*args)

ext/json/lib/json/add/struct.rb View on GitHub

          
            # File tmp/rubies/ruby-2.6.10/ext/json/lib/json/add/struct.rb, line 27
def to_json(*args)
  as_json.to_json(*args)
end

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

          
            static VALUE
rb_struct_values_at(int argc, VALUE *argv, VALUE s)
{
    return rb_get_values_at(s, RSTRUCT_LEN(s), argc, argv, struct_entry);
}

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]

Struct

Passwd

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

Group

Tms

json_create(object)

Struct.new([class_name] [, member_name]+) → StructClass

Struct.new([class_name] [, member_name]+, keyword_init: true) → StructClass

Struct.new([class_name] [, member_name]+) {|StructClass| block } → StructClass

StructClass.new(value, ...) → object

StructClass[value, ...] → object

struct == other → true or false

struct[member] → object

struct[index] → object

struct[member] = obj → obj

struct[index] = obj → obj

as_json(*)

struct.dig(key, ...) → object

struct.each {|obj| block } → struct

struct.each → enumerator

struct.each_pair {|sym, obj| block } → struct

struct.each_pair → enumerator

struct.eql?(other) → true or false

struct.filter {|obj| block } → array

struct.filter → enumerator

struct.hash → integer

struct.inspect → string

struct.length → integer

struct.members → array

struct.select {|obj| block } → array

struct.select → enumerator

struct.size → integer

struct.to_a → array

struct.to_h → hash

struct.to_h {|name, value| block } → hash

to_json(*args)

struct.to_s → string

struct.values → array

struct.values_at(selector, ...) → array