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 is a generator of specific classes, each one of which is defined to hold a set of variables and their accessors. In these examples, we'll call the generated class “CustomerClass,'' and we'll show an example instance of that class as “CustomerInst.''

In the descriptions that follow, the parameter symbol refers to a symbol, which is either a quoted string or a Symbol (such as :name).

Public Class Methods

new( [aString] [, aSym]+> ) → StructClass click to toggle source

new( [aString] [, aSym]+> ) {|StructClass| block } → StructClass

new(arg, ...) → obj

StructClass[arg, ...] → obj

Creates a new class, named by aString, containing accessor methods for the given symbols. If the name aString 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 should start with a capital letter. Assigning a structure class to a constant effectively gives the class the name of the constant.

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

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

Struct::new returns a new Class object, which can then be used to create specific instances of the new structure. The number of actual parameters must be less than or equal to the number of attributes defined for this class; unset parameters default to nil. Passing too many parameters will raise an ArgumentError.

The remaining methods listed in this section (class and instance) are defined for this generated class.

# Create a structure with a name in 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">

 
               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_PTR(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;
}

Public Instance Methods

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

Equality—Returns true if other_struct is equal to this one: they must be of the same class as generated by Struct::new, and the values of all instance variables must be equal (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[symbol] → anObject click to toggle source

struct[fixnum] → anObject

Attribute Reference—Returns the value of the instance variable named by symbol, or indexed (0..length-1) by fixnum. Will raise NameError if the named variable does not exist, or 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)
{
    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_PTR(s)[i];
}

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

struct[fixnum] = obj → obj

Attribute Assignment—Assigns to the instance variable named by symbol or fixnum the value obj and returns it. Will raise a NameError if the named variable does not exist, or an 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)
{
    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);
    return RSTRUCT_PTR(s)[i] = val;
}

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

each → an_enumerator

Calls block once for each instance variable, passing the value as a parameter.

If no block is given, an enumerator is returned instead.

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, rb_struct_size);
    for (i=0; i<RSTRUCT_LEN(s); i++) {
        rb_yield(RSTRUCT_PTR(s)[i]);
    }
    return s;
}

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

each_pair → an_enumerator

Calls block once for each instance variable, passing the name (as a symbol) and the value as parameters.

If no block is given, an enumerator is returned instead.

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, rb_struct_size);
    members = rb_struct_members(s);
    for (i=0; i<RSTRUCT_LEN(s); i++) {
        VALUE key = rb_ary_entry(members, i);
        VALUE value = RSTRUCT_PTR(s)[i];
        rb_yield(rb_assoc_new(key, value));
    }
    return s;
}

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

Two structures are equal if they are the same object, or if all their fields are equal (using 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);
}

hash → fixnum click to toggle source

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

 
               static VALUE
rb_struct_hash(VALUE s)
{
    return rb_exec_recursive_outer(recursive_hash, s, 0);
}

to_s → string click to toggle source

inspect → string

Describe the contents of this struct in a string.

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

Also aliased as: to_s

length → fixnum click to toggle source

Returns the number of instance variables.

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

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

members → array click to toggle source

Returns an array of symbols representing the names of the instance variables.

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 {|i| block } → array click to toggle source

select → an_enumerator

Invokes the block passing in successive elements from struct, returning an array containing those elements for which the 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]

 
               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, rb_struct_size);
    result = rb_ary_new();
    for (i = 0; i < RSTRUCT_LEN(s); i++) {
        if (RTEST(rb_yield(RSTRUCT_PTR(s)[i]))) {
            rb_ary_push(result, RSTRUCT_PTR(s)[i]);
        }
    }

    return result;
}

size → fixnum click to toggle source

Returns the number of instance variables.

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

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

to_a → array click to toggle source

Returns the values for this instance 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_PTR(s));
}

to_h → hash click to toggle source

Returns the values for this instance as a hash with keys corresponding to the instance variable name.

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

 
               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_PTR(s)[i]);
    }
    return h;
}

to_s() click to toggle source

Alias for: inspect

values → array click to toggle source

Returns the values for this instance 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_PTR(s));
}

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

Returns an array containing the elements in self corresponding to the given selector(s). The selectors may be either integer indices or ranges. See also </code>.select<code>.

a = %w{ a b c d e f }
a.values_at(1, 3, 5)
a.values_at(1, 3, 5, 7)
a.values_at(-1, -3, -5, -7)
a.values_at(1..3, 2...5)

 
               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);
}

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