xtd::hash_code Class Reference

Inheritance diagram for xtd::hash_code:

Definition

Combines the hash code for multiple values into a single hash code.

class hash_code : public xtd::object

Namespace

xtd

Library

xtd.core

Examples

The static methods in this class combine the default hash codes of several values.

#include <xtd/xtd>
 
using namespace xtd;
using namespace xtd::collections::generic;
 
struct order_order_line : public object, public iequatable<order_order_line> {
public:
  order_order_line(int order_id, int order_line_id) : order_id_ {order_id}, order_line_id_ {order_line_id} {}
  
  int order_id() const noexcept {return order_id_;}
  int order_line_id() const noexcept {return order_line_id_;}
  
  bool equals(const object& obj) const noexcept override {return is<order_order_line>(obj) && equals(as<order_order_line>(obj));}
  bool equals(const order_order_line& other) const noexcept override {return order_id_ == other.order_id_ && order_line_id_ == other.order_line_id_;}
  
  size get_hash_code() const noexcept override {return hash_code::combine(order_id_, order_line_id_);}
  
private:
  int order_id_ = 0;
  int order_line_id_ = 0;
};
 
auto main() -> int {
  auto set = hash_set<order_order_line> {
    order_order_line {1, 1},
    order_order_line {1, 1},
    order_order_line {1, 2}
  };
  
  console::write_line("Item count: {}.", set.size());
}
 
// This code produces the following output :
//
// Item count: 2.

Remarks

You can use xtd::hash_code to combine multiple values (for example, fields on a structure or class) into a single hash code. This structure has static and instance methods that operate differently:

* The static methods accept a set of several values to combine.

* Two instance methods operate in a streaming fashion, accepting values one at a time.

Warning

It's best-practice to consider hash codes as an implementation detail, as the implementation may change across xtd versions. Do not store hash codes produced by xtd::hash_code in serialized structures, for example, on-disk. xtd::hash_code uses a statically initialized random seed to enforce this best practice, meaning that the hash codes are only deterministic within the scope of an operating system process.

Public Constructors
	hash_code ()=default
	Create a new instance of the class hash_code.

Public Methods
template<typename type_t >
hash_code &	add (const type_t value) noexcept
	Adds a single value to the hash code.
bool	equals (const xtd::object &other) const noexcept override
	Determines whether the specified object is equal to the current object.
xtd::size	get_hash_code () const noexcept override
	Serves as a hash function for a particular type.
xtd::size	to_hash_code () const noexcept
	Calculates the final hash code after consecutive xtd::hash_code::add invocations.

Public Static Methods
template<typename ... args_t>
static xtd::size	combine (args_t... values) noexcept
	Combines values into a hash code.

Additional Inherited Members
Public Member Functions inherited from xtd::object
	object ()=default
	Create a new instance of the ultimate base class object.
virtual type_object	get_type () const noexcept
	Gets the type of the current instance.
template<typename object_t >
xtd::uptr< object_t >	memberwise_clone () const
	Creates a shallow copy of the current object.
virtual xtd::string	to_string () const noexcept
	Returns a xtd::string that represents the current object.
Static Public Member Functions inherited from xtd::object
template<typename object_a_t , typename object_b_t >
static bool	equals (const object_a_t &object_a, const object_b_t &object_b) noexcept
	Determines whether the specified object instances are considered equal.
template<typename object_a_t , typename object_b_t >
static bool	reference_equals (const object_a_t &object_a, const object_b_t &object_b) noexcept
	Determines whether the specified object instances are the same instance.

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The documentation for this class was generated from the following file:

• xtd.core/include/xtd/hash_code.h