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

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

Definition

template<typename type_t>
class xtd::collections::generic::iequality_comparer< type_t >

Defines methods to support the comparison of objects for equality.

Definition

template<typename type_t>
class iequality_comparer interface_

Header

#include <xtd/collections/iequality_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.

Examples

generic_icollection.cpp, and generic_ilist.cpp.

Public Methods
virtual bool	equals (const type_t &x, const type_t &y) const noexcept=0
	Determines whether the specified objects are equal.
virtual xtd::size	get_hash_code (const type_t &obj) const noexcept=0
	Returns a hash code for the specified object.

Member Function Documentation

equals()

template<typename type_t >

virtual bool xtd::collections::generic::iequality_comparer< type_t >::equals ( const type_t &  x, const type_t &  y  ) const

pure virtualnoexcept

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.

get_hash_code()

template<typename type_t >

virtual xtd::size xtd::collections::generic::iequality_comparer< type_t >::get_hash_code ( const type_t &  obj ) const

pure virtualnoexcept

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.

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

• xtd.core/include/xtd/collections/generic/iequality_comparer.h