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

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

Definition

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

Exposes the enumerator, which supports a simple iteration over a collection of a specified type.

Definition

template<class type_t>
class ienumarable interface_

Header

#include <xtd/collections/generic/ienumarable>

Namespace

xtd::collections::generic

Library

xtd.core

Examples

The following example demonstrates how to implement the xtd::collections::generic::ienumerable <type_t> interface. When you implement xtd::collections::generic::ienumerable <type_t>, you must also implement xtd::collections::generic::ienumerator <type_t>.

#include <xtd/xtd>
 
using namespace xtd;
using namespace xtd::io;
using namespace xtd::collections::generic;
 
class program {
public:
  static auto main() -> void {
    test_stream_reader_enumerable();
    console::write_line("---");
    test_reading_file();
  }
  
  static void test_stream_reader_enumerable() {
    // Check the memory before the iterator is used.
    auto memory_before = memory_information::get_used_process_memory();
    auto strings_found = list<string> {};
    // Open a file with the stream_reader_enumerable and check for a string.
    try {
      for (auto line : stream_reader_enumerable {path::combine(path::get_temp_path(), "temp_file.txt")})
        if (line.contains("string to search for")) strings_found.push_back(line);
      console::write_line("Found: {}", strings_found.size());
    } catch (const file_not_found_exception&) {
      console::write_line("This example requires a file named {}.", path::combine(path::get_temp_path(), "temp_file.txt"));
      return;
    }
    
    // Check the memory after the iterator and output it to the console.
    auto memory_after = memory_information::get_used_process_memory();
    console::write_line("Memory Used With Iterator = \t{} kb", (memory_after - memory_before) / 1024);
  }
 
  static void test_reading_file() {
    size memory_before = memory_information::get_used_process_memory();
 
    auto file_contents = list<string> {};
    try {
      auto sr = stream_reader {path::combine(path::get_temp_path(), "temp_file.txt")};
      // Add the file contents to a generic list of strings.
      while (!sr.end_of_stream())
        file_contents.add(sr.read_line());
      sr.close();
    } catch (const file_not_found_exception&) {
      console::write_line("This example requires a file named {}.", path::combine(path::get_temp_path(), "temp_file.txt"));
      return;
    }
    
    // Check for the string.
    auto strings_found = list<string> {};
    for (auto line : file_contents)
      if (line.contains("string to search for")) strings_found.push_back(line);
    console::write_line("Found: {}", strings_found.size());
 
    // Check the memory after when the iterator is not used, and output it to the console.
    auto memory_after = memory_information::get_used_process_memory();
    console::write_line("Memory Used Without Iterator = \t{} kb", (memory_after - memory_before) / 1024);
  }
 
  // you must also implement xtd::collections::generic::ienumerable <type_t> and xtd::collections::generic::ienumerator <type_t>
  class stream_reader_enumerable : public ienumerable<string> {
  private:
    string file_path_;
    
  public:
    stream_reader_enumerable(const string& file_path) : file_path_ {file_path} {}
    
    // Must implement get_enumerator, which returns a new stream_reader_enumerator.
    enumerator<string> get_enumerator() const override {return {new_ptr<stream_reader_enumerator>(file_path_)};}
  };
  
  // When you implement xtd::collections::generic::ienumerable <type_t>, you must also implement xtd::collections::generic::ienumerator <type_t>, which will walk through the contents of the file one line at a time.
  class stream_reader_enumerator : public object, public ienumerator<string> {
  private:
    stream_reader sr_;
    std::optional<string> current_;
 
  public:
    stream_reader_enumerator(const string& file_path) : sr_ {file_path} {}
    ~stream_reader_enumerator() {sr_.close();}
 
    // Implement current, move_next and reset, which are required by ienumerator.
    const string& current() const override {
      if (!current_.has_value()) throw invalid_operation_exception {};
      return current_.value();
    }
        
    bool move_next() override {
      if (sr_.end_of_stream()) current_.reset();
      else current_ = sr_.read_line();
      return current_.has_value();
    }
    
    void reset() override {
      sr_.base_stream()->get().seekg(0, std::ios_base::seekdir::beg);
      current_.reset();
    }
  };
};
 
startup_(program::main);
 
// This code produces the following output :
//
// Found: 2
// Memory Used With Iterator =   0 kb
// ---
// Found: 2
// Memory Used Without Iterator =   64 kb

Remarks

xtd::collections::generic::ienumerable <type_t> is the base interface for collections in the xtd::collections::generic namespace such as xtd::collections::generic::list <type_t>, xtd::collections::generic::dictionary <key_t, value_t>, and xtd::collections::generic::stack <type_t> and other generic collections such as xtd::collections::object_model::observable_collection <type_t> and xtd::collections::concurent::concurrent_stack <type_t>. Collections that implement xtd::collections::generic::ienumerable <type_t> can be enumerated by using the for each statement.

For the non-generic version of this interface, see xtd::collections::ienumerable.

xtd::collections::generic::ienumerable <type_t> contains a single method that you must implement when implementing this interface; xtd::collections::generic::ienumerable::get_enumerator, which returns an xtd::collections::generic::enumerator <type_t> object. The returned xtd::collections::generic::enumerator <type_t> provides the ability to iterate through the collection by exposing a xtd::collections::generic::enumerator::current property.

Examples

generic_ienumerable.cpp, and generic_ienumerable2.cpp.

Public Aliases
using	value_type
	Represents the xtd::collections::generic::ienumerable value type.
using	iterator
	Represents the iterator of xtd::collections::generic::ienumerable value type.
using	const_iterator
	Represents the const iterator of xtd::collections::generic::ienumerable value type.

Public Methods
virtual xtd::collections::generic::enumerator< type_t >	get_enumerator () const =0
	Returns an enumerator that iterates through a collection.

Additional Inherited Members
using	iterator
	Represents the iterator of enumarable value type.
using	const_iterator
	Represents the const iterator of enumarable value type.
using	enumerable_type
	Represents the ienumerable enumerable type.
using	source_type
	Represents the ienumerable source type.
using	ienumerable
	Represents the ienumerable value type.
using	list
	Represents the list value type.
virtual const_iterator	begin () const
	Returns an iterator to the first element of the enumarable.
virtual iterator	begin ()
	Returns an iterator to the first element of the enumarable.
virtual const_iterator	cbegin () const
	Returns an iterator to the first element of the enumarable.
virtual const_iterator	cend () const
	Returns an iterator to the element following the last element of the enumarable.
virtual const_iterator	end () const
	Returns an iterator to the element following the last element of the enumarable.
virtual iterator	end ()
	Returns an iterator to the element following the last element of the enumarable.
type_t	aggregate (const std::function< type_t(const type_t &, const type_t &)> &func) const
	Applies an accumulator function over a sequence.
type_t	aggregate (const type_t &seed, const std::function< type_t(const type_t &, const type_t &)> &func) const
	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.
accumulate_t	aggregate (const accumulate_t &seed, const std::function< accumulate_t(const type_t &, const accumulate_t &)> &func) const
	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.
type_t	aggregate (const type_t &seed, const std::function< type_t(const type_t &, const type_t &)> &func, const std::function< type_t(const type_t &)> &result_selector) const
	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.
result_t	aggregate (const accumulate_t &seed, const std::function< accumulate_t(const type_t &, const accumulate_t &)> &func, const std::function< result_t(const accumulate_t &)> &result_selector) const
	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.
bool	all (const std::function< bool(const type_t &)> &predicate) const
	Determines whether all elements of a sequence satisfy a condition.
bool	any () const noexcept
	Determines whether a sequence contains any elements.
bool	any (const std::function< bool(const type_t &)> &predicate) const
	Determines whether any element of a sequence satisfies a condition.
const ienumerable< type_t > &	append (const type_t &element) const noexcept
	Appends a value to the end of the sequence.
const ienumerable< type_t > &	as_enumerable () const noexcept
	Returns the input typed as xtd::collections::generic::ienumerable <type_t>.
auto	average () const noexcept
	Computes the average of a sequence of source_t values.
const ienumerable< result_t > &	cast () const noexcept
	Casts the elements of an xtd::collections::generic::ienumerable to the specified type.
const ienumerable< xtd::array< type_t > > &	chunk (size_t size) const
	Splits the elements of a sequence into chunks of size at most size.
const ienumerable< type_t > &	concat (const ienumerable< type_t > &second) const noexcept
	Concatenates two sequences.
bool	contains (const type_t &value) const noexcept
	Determines whether a sequence contains a specified element by using the default equality comparer.
bool	contains (const type_t &value, const xtd::collections::generic::iequality_comparer< type_t > &comparer) const noexcept
	Determines whether a sequence contains a specified element by using a specified equality comparer.
size_t	count () const noexcept
	Returns the number of elements in current sequence.
size_t	count (const std::function< bool(const type_t &)> &predicate) const noexcept
	Returns a number that represents how many elements in the specified sequence satisfy a condition.
xtd::size	count (const type_t &value) const noexcept
	Returns the number of elements with the specified value.
const ienumerable< key_value_pair< key_t, xtd::size > > &	count_by (const std::function< key_t(const type_t &)> &key_selector) const noexcept
	Returns the count of elements in the current sequence grouped by key.
const ienumerable< key_value_pair< key_t, xtd::size > > &	count_by (const std::function< key_t(const type_t &)> &key_selector, const iequality_comparer< key_t > &key_comparer) const noexcept
	Returns the count of elements in the current sequence grouped by key.
const ienumerable< type_t > &	default_if_empty () const noexcept
	Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the current sequence is empty.
const ienumerable< type_t > &	default_if_empty (const type_t &default_value) const noexcept
	Returns the elements of the specified sequence or the specified value in a singleton collection if the current sequence is empty.
type_t	first_or_default (const std::function< bool(const type_t &)> &predicate, const type_t &default_value) const noexcept
	Returns the first element of the sequence that satisfies a condition, or a specified default value if no such element is found.
type_t	first_or_default (const std::function< bool(const type_t &)> &predicate) const noexcept
	Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
type_t	first_or_default (const type_t default_value) const noexcept
	Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
type_t	first_or_default () const noexcept
	Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
const ienumerable< result_t > &	select (const std::function< result_t(const type_t &)> &selector) const
	Projects each element of a sequence into a new form.
const ienumerable< type_t > &	select (const std::function< type_t(const type_t &)> &selector) const
	Projects each element of a sequence into a new form.
const ienumerable< result_t > &	select (const std::function< result_t(const type_t &, size_t index)> &selector) const
	Projects each element of a sequence into a new form by incorporating the element's index.
const ienumerable< type_t > &	select (const std::function< type_t(const type_t &, size_t index)> &selector) const
	Projects each element of a sequence into a new form by incorporating the element's index.
const list< type_t > &	to_list () const noexcept
	Creates a xtd::collections::generic::list <type_t> from an xtd::collections::generic::ienumerable <type_t>.
const ienumerable< type_t > &	where (const std::function< bool(const type_t &)> &predicate) const
	Filters a sequence of values based on a predicate.
const ienumerable< type_t > &	where (const std::function< bool(const type_t &, size_t)> &predicate) const
	Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.
static target_collection_t::const_iterator	to_iterator (typename source_collection_t::const_iterator &value, const source_collection_t &source_collection, const target_collection_t &target_collection) noexcept
	Converts source iterator to target iterator.
static target_collection_t::iterator	to_iterator (typename source_collection_t::iterator &value, const source_collection_t &source_collection, const target_collection_t &target_collection) noexcept
	Converts source iterator to target iterator.
static target_collection_t::const_iterator	to_iterator (typename source_collection_t::const_iterator &value, source_collection_t &source_collection, target_collection_t &target_collection) noexcept
	Converts source iterator to target iterator.
static target_collection_t::iterator	to_iterator (typename source_collection_t::iterator &value, source_collection_t &source_collection, target_collection_t &target_collection) noexcept
	Converts source iterator to target iterator.

Member Typedef Documentation

value_type

template<class type_t>

using xtd::collections::generic::ienumerable< type_t >::value_type

Represents the xtd::collections::generic::ienumerable value type.

iterator

template<class type_t>

using xtd::collections::generic::ienumerable< type_t >::iterator

Represents the iterator of xtd::collections::generic::ienumerable value type.

const_iterator

template<class type_t>

using xtd::collections::generic::ienumerable< type_t >::const_iterator

Represents the const iterator of xtd::collections::generic::ienumerable value type.

Member Function Documentation

get_enumerator()

template<class type_t>

virtual xtd::collections::generic::enumerator< type_t > xtd::collections::generic::ienumerable< type_t >::get_enumerator ( ) const

pure virtual

Returns an enumerator that iterates through a collection.

Returns

An xtd::collections::generic::enumerator object that can be used to iterate through the collection.

Implemented in xtd::basic_string< char_t, traits_t, allocator_t >, xtd::basic_string< char >, xtd::basic_string< char >, xtd::basic_string< xtd::char16 >, xtd::basic_string< xtd::char16 >, xtd::basic_string< xtd::char32 >, xtd::basic_string< xtd::char32 >, xtd::basic_string< xtd::char8 >, xtd::basic_string< xtd::char8 >, xtd::basic_string< xtd::wchar >, and xtd::basic_string< xtd::wchar >.

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

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