class Struct

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

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

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

Public Class Methods

json_create(object) click to toggle source

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

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

new([class_name] [, member_name]+) → StructClass click to toggle source

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

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

new(value, ...) → object

StructClass[value, ...] → object

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>

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);
    OBJ_WB_UNPROTECT(rest);
    tbl = RHASH_TBL_RAW(rest);
    for (i=0; i<argc; i++) {
        VALUE mem = rb_to_symbol(argv[i]);
        if (rb_is_attrset_sym(mem)) {
            rb_raise(rb_eArgError, "invalid struct member: %"PRIsVALUE, mem);
        }
        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;
}

Public Instance Methods

struct == other → true or false click to toggle source

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

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);
}

struct[member] → object click to toggle source

struct[index] → object

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"

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);
}

struct[member] = obj → obj click to toggle source

struct[index] = obj → obj

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"

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;
}

as_json(*) click to toggle source

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

# File 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 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"

Alias for: to_a

deconstruct_keys(p1) click to toggle source

static VALUE
rb_struct_deconstruct_keys(VALUE s, VALUE keys)
{
    VALUE h;
    long i;

    if (NIL_P(keys)) {
        return rb_struct_to_h(s);
    }
    if (UNLIKELY(!RB_TYPE_P(keys, T_ARRAY))) {
        rb_raise(rb_eTypeError,
                 "wrong argument type %"PRIsVALUE" (expected Array or nil)",
                 rb_obj_class(keys));

    }
    if (RSTRUCT_LEN(s) < RARRAY_LEN(keys)) {
        return rb_hash_new_with_size(0);
    }
    h = rb_hash_new_with_size(RARRAY_LEN(keys));
    for (i=0; i<RARRAY_LEN(keys); i++) {
        VALUE key = RARRAY_AREF(keys, i);
        int i = rb_struct_pos(s, &key);
        if (i < 0) {
            return h;
        }
        rb_hash_aset(h, key, RSTRUCT_GET(s, i));
    }
    return h;
}

dig(key, *identifiers) → object click to toggle source

Finds and returns the object in nested objects that is specified by key and identifiers. The nested objects may be instances of various classes. See Dig Methods.

Examples:

Foo = Struct.new(:a)
f = Foo.new(Foo.new({b: [1, 2, 3]}))
f.dig(:a) # => #<struct Foo a={:b=>[1, 2, 3]}>
f.dig(:a, :a) # => {:b=>[1, 2, 3]}
f.dig(:a, :a, :b) # => [1, 2, 3]
f.dig(:a, :a, :b, 0) # => 1
f.dig(:b, 0) # => nil

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);
}

each {|obj| block } → struct click to toggle source

each → enumerator

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

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;
}

each_pair {|sym, obj| block } → struct click to toggle source

each_pair → enumerator

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

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_pair_yield_optimizable()) {
        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;
}

eql?(other) → true or false click to toggle source

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?).

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);
}

filter {|obj| block } → array

filter → enumerator

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.

Alias for: select

hash → integer click to toggle source

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

See also Object#hash.

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 ST2FIX(h);
}

inspect → string click to toggle source

Returns a description of this struct as a string.

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

Also aliased as: to_s

length → integer

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

Alias for: size

members → array click to toggle source

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]

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

select {|obj| block } → array click to toggle source

select → enumerator

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.

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;
}

Also aliased as: filter

size → integer click to toggle source

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

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

Also aliased as: length

to_a → array click to toggle source

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"

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

Also aliased as: values, deconstruct

to_h → hash click to toggle source

to_h {|name, value| block } → hash

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"

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;
}

to_json(*args) click to toggle source

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

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

to_s → string

Returns a description of this struct as a string.

Alias for: inspect

values → array

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"

Alias for: to_a

values_at(selector, ...) → array click to toggle source

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]

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);
}