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Class: Struct

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, ::Enumerable
Inherits: Object
Defined in: struct.c,
process.c,
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 .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

Class Method Summary

Instance Method Summary

::Enumerable - Included

#all?

Passes each element of the collection to the given block.
#any?

Passes each element of the collection to the given block.
#chunk

Enumerates over the items, chunking them together based on the return value of the block.
#chunk_while

Creates an enumerator for each chunked elements.
#collect

Alias for Enumerable#map.
#collect_concat

Alias for Enumerable#flat_map.
#count

Returns the number of items in enum through enumeration.
#cycle

Calls block for each element of enum repeatedly n times or forever if none or nil is given.
#detect

Alias for Enumerable#find.
#drop

Drops first n elements from enum, and returns rest elements in an array.
#drop_while

Drops elements up to, but not including, the first element for which the block returns nil or false and returns an array containing the remaining elements.
#each_cons

Iterates the given block for each array of consecutive <n> elements.
#each_entry

Calls block once for each element in self, passing that element as a parameter, converting multiple values from yield to an array.
#each_slice

Iterates the given block for each slice of <n> elements.
#each_with_index

Calls block with two arguments, the item and its index, for each item in enum.
#each_with_object

Iterates the given block for each element with an arbitrary object given, and returns the initially given object.
#entries

Alias for Enumerable#to_a.
#find

Passes each entry in enum to block.
#find_all

Alias for Enumerable#select.
#find_index

Compares each entry in enum with value or passes to block.
#first

Returns the first element, or the first n elements, of the enumerable.
#flat_map

Returns a new array with the concatenated results of running block once for every element in enum.
#grep

Returns an array of every element in enum for which Pattern === element.
#grep_v

Inverted version of Enumerable#grep.
#group_by

Groups the collection by result of the block.
#include?

Alias for Enumerable#member?.
#inject

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator.
#lazy

Returns a lazy enumerator, whose methods map/collect, flat_map/collect_concat, select/find_all, reject, grep, grep_v, zip, take, take_while, drop, and drop_while enumerate values only on an as-needed basis.
#map

Returns a new array with the results of running block once for every element in enum.
#max

Returns the object in enum with the maximum value.
#max_by

Returns the object in enum that gives the maximum value from the given block.
#member?

Returns true if any member of enum equals obj.
#min

Returns the object in enum with the minimum value.
#min_by

Returns the object in enum that gives the minimum value from the given block.
#minmax

Returns a two element array which contains the minimum and the maximum value in the enumerable.
#minmax_by

Returns a two element array containing the objects in enum that correspond to the minimum and maximum values respectively from the given block.
#none?

Passes each element of the collection to the given block.
#one?

Passes each element of the collection to the given block.
#partition

Returns two arrays, the first containing the elements of enum for which the block evaluates to true, the second containing the rest.
#reduce

Alias for Enumerable#inject.
#reject

Returns an array for all elements of enum for which the given block returns false.
#reverse_each

Builds a temporary array and traverses that array in reverse order.
#select

Returns an array containing all elements of enum for which the given block returns a true value.
#slice_after

Creates an enumerator for each chunked elements.
#slice_before

Creates an enumerator for each chunked elements.
#slice_when

Creates an enumerator for each chunked elements.
#sort

Returns an array containing the items in enum sorted.
#sort_by

Sorts enum using a set of keys generated by mapping the values in enum through the given block.
#sum

Returns the sum of elements in an ::Enumerable.
#take

Returns first n elements from enum.
#take_while

Passes elements to the block until the block returns nil or false, then stops iterating and returns an array of all prior elements.
#to_a

Returns an array containing the items in enum.
#to_h

Returns the result of interpreting enum as a list of [key, value] pairs.
#uniq

Returns a new array by removing duplicate values in self.
#zip

Takes one element from enum and merges corresponding elements from each args.

Constructor Details

.new([class_name] [, member_name]+) ⇒ Struct .new([class_name] [, member_name]+, keyword_init: true) ⇒ Struct .new([class_name] [, member_name]+) {|StructClass| ... } ⇒ Struct StructClass.new(value, ...) ⇒ Object StructClass ⇒ 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 ::Class, 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>
[ GitHub ] 

  


# File 'struct.c', line 517



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;
}


  






  

  

    #initialize(*args)  
  

  [ GitHub ]


  

  


# File 'struct.c', line 615



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 (argc > 0 && RTEST(rb_struct_s_keyword_init(klass))) {
	struct struct_hash_set_arg arg;
	if (argc > 2 || !RB_TYPE_P(argv[0], T_HASH)) {
	    rb_raise(rb_eArgError, "wrong number of arguments (given %d, expected 0)", argc);
	}
	rb_mem_clear((VALUE *)RSTRUCT_CONST_PTR(self), n);
	arg.self = self;
	arg.unknown_keywords = Qnil;
	rb_hash_foreach(argv[0], struct_hash_set_i, (VALUE)&arg);
	if (arg.unknown_keywords != Qnil) {
	    rb_raise(rb_eArgError, "unknown keywords: %s",
		     RSTRING_PTR(rb_ary_join(arg.unknown_keywords, rb_str_new2(", "))));
	}
    }
    else {
	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;
}


  







Instance Method Details



  

    #==(other)  ⇒ Boolean   



  

    

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


  



  [ GitHub ]


  

  


# File 'struct.c', line 1119



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);
}


  








  

    

      #[](member)  ⇒ Object 
      #[](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"


  





  


  [ GitHub ]


  

  


# File 'struct.c', line 976



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);
}


  








  

    

      #[]=(member, obj)  ⇒ Object 
      #[]=(index, obj)  ⇒ Object 
    

  



  

    

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"


  





  


  [ GitHub ]


  

  


# File 'struct.c', line 1003



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;
}


  








  

    #dig(key, ...)  ⇒ 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


  



  [ GitHub ]


  

  


# File 'struct.c', line 1232



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| ... } ⇒ Struct 
      #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


  





  


  [ GitHub ]


  

  


# File 'struct.c', line 731



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| ... } ⇒ Struct 
      #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


  





  


  [ GitHub ]


  

  


# File 'struct.c', line 762



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;
}


  








  

    #eql?(other)  ⇒ Boolean   



  

    

::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?).


  



  [ GitHub ]


  

  


# File 'struct.c', line 1185



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  ⇒ Integer   



  

    

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



See also Object#hash.


  



  [ GitHub ]


  

  


# File 'struct.c', line 1141



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);
}


  








  

    #initialize_copy(s)  
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'struct.c', line 889



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;
}


  








  

    

      #to_s  ⇒ String 
      #inspect  ⇒ String 
    

  



  

    

Alias for #to_s.


  





  








  

    

      #length  ⇒ Integer 
      #size  ⇒ Integer 
    

    Also known as: #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


  





  


  [ GitHub ]


  

  


# File 'struct.c', line 1210



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


  








  

    #members  ⇒ Array   



  

    

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]


  



  [ GitHub ]


  

  


# File 'struct.c', line 204



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


  








  

    

      #select {|obj| ... } ⇒ Array 
      #select  ⇒ 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]


  





  


  [ GitHub ]


  

  


# File 'struct.c', line 1070



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;
}


  








  

    

      #length  ⇒ Integer 
      #size  ⇒ Integer 
    

  



  

    

Alias for #length.


  





  








  

    

      #to_a  ⇒ Array 
      #values  ⇒ Array 
    

    Also known as: #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"


  





  


  [ GitHub ]


  

  


# File 'struct.c', line 858



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


  








  

    #to_h  ⇒ Hash   



  

    

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"


  



  [ GitHub ]


  

  


# File 'struct.c', line 875



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;

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


  








  

    

      #to_s  ⇒ String 
      #inspect  ⇒ String 
    

    Also known as: #inspect
  



  

    

Returns a description of this struct as a string.


  



  [ GitHub ]


  

  


# File 'struct.c', line 840



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


  








  

    

      #to_a  ⇒ Array 
      #values  ⇒ Array 
    

  



  

    

Alias for #to_a.


  





  








  

    #values_at(selector, ...)  ⇒ Array   



  

    

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]


  



  [ GitHub ]


  

  


# File 'struct.c', line 1050



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);
}