xtd::collections::generic::equality_comparer< type_t > Class Template Reference

Inheritance diagram for xtd::collections::generic::equality_comparer< type_t >:

Definition

template<class type_t>
class xtd::collections::generic::equality_comparer< type_t >

Provides a base class for implementations of the xtd::collections::generic::iequality_comparer <type_t> generic interface.

Definition

template<class type_t>
class equality_comparer : public xtd::collections::generic::iequality_comparer<type_t>

Header

#include <xtd/collections/generic/equality_comparer>

Namespace

xtd::collections::generic

Library

xtd.core

Remarks

This interface allows the implementation of customized equality comparison for collections. That is, you can create your own definition of equality for type type_t, and specify that this definition be used with a collection type that accepts the xtd::collections::generic::iequality_comparer <type_t> generic interface. In the xtd framework, constructors of the xtd::collections::generic::dictionary <key_t, value_t> generic collection type accept this interface.

A default implementation of this interface is provided by the xtd::collections::generic::equality_comparer::default_equality_comparer property of the xtd::collections::generic::equality_comparer <type_t> generic class. The xtd::string_comparer class implements xtd::collections::generic::iequality_comparer <type_t> of type xtd::string.

This interface supports only equality comparisons. Customization of comparisons for sorting and ordering is provided by the xtd::collections::generic::icomparer <type_t> generic interface.

We recommend that you derive from the xtd::collections::generic::equality_comparer <type_t> class instead of implementing the xtd::collections::generic::iequality_comparer <type_t> interface, because the xtd::collections::generic::equality_comparer <type_t> class tests for equality using the xtd::iequatable::equals method instead of the xtd::object::equals method. This is consistent with the contains, index_of, last_index_of, and remove methods of the xtd::collections::generic::dictionary <key_t, value_t> class and other generic collections.

Public Static Properties
static auto	default_equality_comparer () -> const equality_comparer &
	Gets the default equality comparer for the type specified by the generic argument.

Public Methods
auto	equals (const type_t &x, const type_t &y) const noexcept -> bool override
	Determines whether the specified objects are equal.
auto	get_hash_code (const type_t &obj) const noexcept -> xtd::size override
	Returns a hash code for the specified object.

Additional Inherited Members

Member Function Documentation

default_equality_comparer()

template<class type_t>

auto xtd::collections::generic::equality_comparer< type_t >::default_equality_comparer ( ) -> const equality_comparer &

inlinestatic

Gets the default equality comparer for the type specified by the generic argument.

Returns

The default instance of the xtd::collections::generic::equality_comparer <type_t> class.

equals()

template<class type_t>

auto xtd::collections::generic::equality_comparer< type_t >::equals ( const type_t & x, const type_t & y ) const -> bool

inlinenodiscardoverridevirtualnoexcept

Determines whether the specified objects are equal.

Parameters

x	The first object of type type_t to compare.
y	The seco,d object of type type_t to compare.

Returns

true if the specified objects are equal; otherwise, false.

Remarks

Implement this method to provide a customized equality comparison for type type_t.

Notes to Implementers

Implementations are required to ensure that if the xtd::collections::generic::iequality_comparer::equals method returns true for two objects x and y, then the value returned by the xtd::collections::generic::iequality_comparer::get_hash_code method for x must equal the value returned for y. The xtd::collections::generic::iequality_comparer::equals method is reflexive, symmetric, and transitive. That is, it returns true if used to compare an object with itself; true for two objects x and y if it is true for y and x; and true for two objects x and z if it is true for x and y and also true for y and z.

Implements xtd::collections::generic::iequality_comparer< type_t >.

get_hash_code()

template<class type_t>

auto xtd::collections::generic::equality_comparer< type_t >::get_hash_code ( const type_t & obj ) const -> xtd::size

inlinenodiscardoverridevirtualnoexcept

Returns a hash code for the specified object.

Parameters

obj	The xtd::object for which a hash code is to be returned.

Returns

A hash code for the specified object.

Remarks

Implement this method to provide a customized hash code for type type_t, corresponding to the customized equality comparison provided by the xtd::collections::generic::iequality_comparer::equals method.

Notes to Implementers

Implementations are required to ensure that if the xtd::collections::generic::iequality_comparer::equals method returns true for two objects x and y, then the value returned by the xtd::collections::generic::iequality_comparer::get_hash_code method for x must equal the value returned for y.

Implements xtd::collections::generic::iequality_comparer< type_t >.

---

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

• xtd.core/include/xtd/collections/generic/equality_comparer.hpp