Arp::Base::Core::IEnumerator< T > Class Template Reference

Declares the interface of the enumerator pattern, which is leaned on .NET enumerator idiom. More...

#include <IEnumerator.hxx>

Inheritance diagram for Arp::Base::Core::IEnumerator< T >:

Public Types
using	Ptr = std::shared_ptr< IEnumerator >
	The smart pointer type of this interface.
using	ValueType = T
	Type of the enumerated values

Public Member Functions
	IEnumerator (void)=default
	Constructs an IEnumerator instance.
	IEnumerator (const IEnumerator &arg)=default
	Deleted copy constructor.
	IEnumerator (IEnumerator &&arg) noexcept=default
	Move constructor.
IEnumerator &	operator= (const IEnumerator &arg)=default
	Deleted copy-assignment IEnumerator.
IEnumerator &	operator= (IEnumerator &&arg) noexcept=default
	Move-assignment operator.
virtual	~IEnumerator (void)=default
	Destructs this instance and frees all resources.
virtual bool	MoveNext (void)=0
	Moves this enumerator to the next position. More...
virtual T	GetCurrent (void)=0
	Gets the element at the current position. More...

Detailed Description

template<class T>
class Arp::Base::Core::IEnumerator< T >

Declares the interface of the enumerator pattern, which is leaned on .NET enumerator idiom.

Template Parameters

T	The element type of the container or collection, respectively.

The enumerator pattern is more easy to implement and to use, because the C++ iterator idiom always requires two arguments (begin, end) when defining algorithms or other operations working on containers or collections.

There is one big difference between iterators and enumerators: When a begin iterator is created it points to the first position of the container/collection immediately. In contrast the enumerator has to be moved once after creation before accessing the first element of a container/collection. Thus, iterators are mostly used with for loops (or range based for loops), but enumerators should always be used with while loops as shown in the following example:

IEnumerator<Any> e = GetAnyEnumerator();
while(e.MoveNext())
{
    // do anything with e.GetCurrent()
}

This interface might also be used with a reference type or even const reference type as template parameter, e.g.

IEnumerator<Any&> e = GetAnyRefEnumerator();
while(e.MoveNext())
{
    Any& item = e.GetCurrent(); // no copy of e.Current
}
 
IEnumerator<const Any&> e = GetAnyConstRefEnumerator();
while(e.MoveNext())
{
    const Any& item = e.GetCurrent(); // no copy of e.Current, item is not mutable
}

Member Function Documentation

GetCurrent()

template<class T >

virtual T Arp::Base::Core::IEnumerator< T >::GetCurrent ( void  )

pure virtual

Gets the element at the current position.

Returns

The element at the current position.

Depending on the template parameter type of this interface, a reference or even const reference might be returned.

Exceptions

InvalidOperationException

When GetCurrent() is called before MoveNext() or after MoveNext() has returned false once.

Implemented in Arp::Base::Core::Enumerator< T >::Composite< T >, Arp::Base::Core::Enumerator< T >::Empty< T >, Arp::Base::Core::Enumerator< T >::Filter< T >, Arp::Base::Core::Enumerator< T >, Arp::Base::Core::Enumerator< const DataInfo & >, Arp::Base::Core::Enumerator< ChildTypeInfo >, Arp::Base::Core::Enumerator< TypeInfo >, Arp::Base::Core::Enumerator< const String & >, Arp::Base::Core::Enumerator< T >::StackComposite< T >, Arp::Base::Core::Enumerator< T >::StlAdapter< T >, Arp::Base::Core::Enumerator< T >::Transform< T >, Arp::System::Commons::Io::Directory::Enumerator< Iterator >, Arp::System::Commons::Io::Directory::SearchEnumerator< Iterator >, and Arp::System::Commons::Io::Directory::EmptyEnumerator.

MoveNext()

template<class T >

virtual bool Arp::Base::Core::IEnumerator< T >::MoveNext ( void  )

pure virtual

Moves this enumerator to the next position.

Returns

false if the end of the container/collections/enumeration has reached, otherwise true.

See also

IEnumerator

Implemented in Arp::Base::Core::Enumerator< T >::Composite< T >, Arp::Base::Core::Enumerator< T >::Empty< T >, Arp::Base::Core::Enumerator< T >::Filter< T >, Arp::Base::Core::Enumerator< T >::StackComposite< T >, Arp::Base::Core::Enumerator< T >::StlAdapter< T >, Arp::Base::Core::Enumerator< T >::Transform< T >, Arp::Plc::Commons::Meta::TypeSystem::TypeDefinition::ChildTypeInfoEnumerator, Arp::Plc::Commons::Meta::TypeSystem::TypeDomain::TypeInfoEnumerator, Arp::System::Commons::Configuration::PlaceholderExpression::Enumerator, Arp::System::Commons::Io::Directory::Enumerator< Iterator >, Arp::System::Commons::Io::Directory::SearchEnumerator< Iterator >, and Arp::System::Commons::Io::Directory::EmptyEnumerator.

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

• Arp/Base/Core/IEnumerator.hxx