Class: Struct

Inherits:
Object show all
Includes:
Enumerable
Defined in:
struct.c

Overview

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).

Constant Summary

Tms =

for the backward compatibility

rb_cProcessTms

Class Method Summary (collapse)

Instance Method Summary (collapse)

Methods included from Enumerable

#all?, #any?, #chunk, #collect, #collect_concat, #count, #cycle, #detect, #drop, #drop_while, #each_cons, #each_entry, #each_slice, #each_with_index, #each_with_object, #entries, #find, #find_all, #find_index, #first, #flat_map, #grep, #group_by, #include?, #inject, #lazy, #map, #max, #max_by, #member?, #min, #min_by, #minmax, #minmax_by, #none?, #one?, #partition, #reduce, #reject, #reverse_each, #slice_before, #sort, #sort_by, #take, #take_while, #zip

Constructor Details

- (Object) initialize



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# File 'struct.c', line 437

static VALUE
rb_struct_initialize_m(int argc, const VALUE *argv, VALUE self)
{
    VALUE klass = rb_obj_class(self);
    long i, n;

    rb_struct_modify(self);
    n = num_members(klass);
    if (n < argc) {
	rb_raise(rb_eArgError, "struct size differs");
    }
    for (i=0; i<argc; i++) {
	RSTRUCT_SET(self, i, argv[i]);
    }
    if (n > argc) {
	rb_mem_clear((VALUE *)RSTRUCT_CONST_PTR(self)+argc, n-argc);
    }
    return Qnil;
}

Class Method Details

+ (StructClass) new([class_name][, member_name]) + (StructClass) new([class_name][, member_name]) {|StructClass| ... } + (Object) new(value, ...) + (Object) [](value, ...)

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">

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.

# 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">

Overloads:

  • + (StructClass) new([class_name][, member_name])

    Returns:

    • (StructClass)
  • + (StructClass) new([class_name][, member_name]) {|StructClass| ... }

    Yields:

    • (StructClass)

    Returns:

    • (StructClass)
  • + (Object) new(value, ...)

    Returns:

  • + (Object) [](value, ...)

    Returns:



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# File 'struct.c', line 386

static VALUE
rb_struct_s_def(int argc, VALUE *argv, VALUE klass)
{
    VALUE name, rest;
    long i;
    VALUE st;
    ID id;

    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
    name = argv[0];
    if (SYMBOL_P(name)) {
	name = Qnil;
    }
    else {
	--argc;
	++argv;
    }
    rest = rb_ary_tmp_new(argc);
    for (i=0; i<argc; i++) {
	id = rb_to_id(argv[i]);
	RARRAY_ASET(rest, i, ID2SYM(id));
	rb_ary_set_len(rest, i+1);
    }
    if (NIL_P(name)) {
	st = anonymous_struct(klass);
    }
    else {
	st = new_struct(name, klass);
    }
    setup_struct(st, rest);
    if (rb_block_given_p()) {
	rb_mod_module_eval(0, 0, st);
    }

    return st;
}

Instance Method Details

- (Boolean) ==(other)

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

Returns:

  • (Boolean)


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# File 'struct.c', line 939

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);
}

- (Object) [](member) - (Object) [](index)

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"

Overloads:



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# File 'struct.c', line 748

VALUE
rb_struct_aref(VALUE s, VALUE idx)
{
    long i;

    if (RB_TYPE_P(idx, T_SYMBOL)) {
	return rb_struct_aref_id(s, SYM2ID(idx));
    }
    else if (RB_TYPE_P(idx, T_STRING)) {
	ID id = rb_check_id(&idx);
	if (!id) {
	    rb_name_error_str(idx, "no member '%"PRIsVALUE"' in struct",
			      QUOTE(idx));
	}
	return rb_struct_aref_id(s, id);
    }

    i = NUM2LONG(idx);
    if (i < 0) i = RSTRUCT_LEN(s) + i;
    if (i < 0)
        rb_raise(rb_eIndexError, "offset %ld too small for struct(size:%ld)",
		 i, RSTRUCT_LEN(s));
    if (RSTRUCT_LEN(s) <= i)
        rb_raise(rb_eIndexError, "offset %ld too large for struct(size:%ld)",
		 i, RSTRUCT_LEN(s));
    return RSTRUCT_GET(s, i);
}

- (Object) []=(name) - (Object) []=(index)

Attribute Assignment—Sets the value of the given struct member or the member at the given index. Raises NameError if the name 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"

Overloads:



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# File 'struct.c', line 818

VALUE
rb_struct_aset(VALUE s, VALUE idx, VALUE val)
{
    long i;

    if (RB_TYPE_P(idx, T_SYMBOL)) {
	return rb_struct_aset_id(s, SYM2ID(idx), val);
    }
    if (RB_TYPE_P(idx, T_STRING)) {
	ID id = rb_check_id(&idx);
	if (!id) {
	    rb_name_error_str(idx, "no member '%"PRIsVALUE"' in struct",
			      QUOTE(idx));
	}
	return rb_struct_aset_id(s, id, val);
    }

    i = NUM2LONG(idx);
    if (i < 0) i = RSTRUCT_LEN(s) + i;
    if (i < 0) {
        rb_raise(rb_eIndexError, "offset %ld too small for struct(size:%ld)",
		 i, RSTRUCT_LEN(s));
    }
    if (RSTRUCT_LEN(s) <= i) {
        rb_raise(rb_eIndexError, "offset %ld too large for struct(size:%ld)",
		 i, RSTRUCT_LEN(s));
    }
    rb_struct_modify(s);
    RSTRUCT_SET(s, i, val);
    return val;
}

- (Object) each {|obj| ... } - (Object) each

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

Overloads:

  • - (Object) each {|obj| ... }

    Yields:

    • (obj)


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# File 'struct.c', line 540

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;
}

- (Object) each_pair {|sym, obj| ... } - (Object) each_pair

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

Overloads:

  • - (Object) each_pair {|sym, obj| ... }

    Yields:

    • (sym, obj)


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# File 'struct.c', line 571

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;
}

- (Boolean) eql?(other)

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:

  • (Boolean)

Returns:

  • (Boolean)


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# File 'struct.c', line 1003

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);
}

- (Fixnum) hash

Returns a hash value based on this struct's contents (see Object#hash).

Returns:



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# File 'struct.c', line 959

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

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

- (Object) initialize_copy

:nodoc:



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# File 'struct.c', line 698

VALUE
rb_struct_init_copy(VALUE copy, VALUE s)
{
    long i, len;

    if (!OBJ_INIT_COPY(copy, s)) return copy;
    if (RSTRUCT_LEN(copy) != RSTRUCT_LEN(s)) {
	rb_raise(rb_eTypeError, "struct size mismatch");
    }

    for (i=0, len=RSTRUCT_LEN(copy); i<len; i++) {
	RSTRUCT_SET(copy, i, RSTRUCT_GET(s, i));
    }

    return copy;
}

- (String) to_s - (String) inspect Also known as: to_s

Describe the contents of this struct in a string.

Overloads:



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# File 'struct.c', line 649

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

- (Fixnum) length - (Fixnum) size

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

Overloads:



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# File 'struct.c', line 1028

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

- (Array) members

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]

Returns:



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# File 'struct.c', line 83

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

- (Array) select {|i| ... } - (Object) select

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 % 2).zero? }   #=> [22, 44, 66]

Overloads:

  • - (Array) select {|i| ... }

    Yields:

    • (i)

    Returns:



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# File 'struct.c', line 890

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;
}

- (Fixnum) length - (Fixnum) size

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

Overloads:



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# File 'struct.c', line 1028

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

- (Array) to_a - (Array) values

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"

Overloads:



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# File 'struct.c', line 667

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

- (Hash) to_h

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"

Returns:



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# File 'struct.c', line 684

static VALUE
rb_struct_to_h(VALUE s)
{
    VALUE h = rb_hash_new();
    VALUE members = rb_struct_members(s);
    long i;

    for (i=0; i<RSTRUCT_LEN(s); i++) {
	rb_hash_aset(h, rb_ary_entry(members, i), RSTRUCT_GET(s, i));
    }
    return h;
}

- (Array) to_a - (Array) values

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"

Overloads:



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# File 'struct.c', line 667

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

- (Array) values_at(selector, ...)

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]

Returns:



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# File 'struct.c', line 870

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);
}