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

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

Definition

template<typename 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<typename type_t>
class ienumarable interface_

Header

#include <xtd/collections/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 = array<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 = array<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 {csf_};
      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.

Public Aliases
using	iterator = typename enumerable_iterators< type_t, ienumerable< type_t > >::iterator
	Represents the iterator of xtd::collections::generic::ienumerable value type.
using	const_iterator = typename enumerable_iterators< type_t, ienumerable< type_t > >::const_iterator
	Represents the const iterator of xtd::collections::generic::ienumerable value type.

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

Additional Inherited Members
Public Types inherited from xtd::collections::generic::enumerable_iterators< type_t, ienumerable< type_t > >
using	const_iterator = const iterator
	Represents the const iterator of enumarable value type.
Public Member Functions inherited from xtd::collections::generic::enumerable_iterators< type_t, ienumerable< type_t > >
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.

Member Typedef Documentation

iterator

template<typename type_t >

using xtd::collections::generic::ienumerable< type_t >::iterator = typename enumerable_iterators<type_t, ienumerable<type_t> >::iterator

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

const_iterator

template<typename type_t >

using xtd::collections::generic::ienumerable< type_t >::const_iterator = typename enumerable_iterators<type_t, ienumerable<type_t> >::const_iterator

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

Member Function Documentation

get_enumerator()

template<typename type_t >

virtual 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_array< type_t, allocator_t >, xtd::basic_array< type_t, allocator_t >, xtd::basic_string< char_t, traits_t, allocator_t >, xtd::collections::generic::list< type_t, allocator_t >, and xtd::collections::object_model::read_only_collection< type_t >.

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

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