csv::CSVReader::iterator Class Reference

An input iterator capable of handling large files. More...

#include <csv_reader.hpp>

Public Member Functions
	iterator (CSVReader *reader)
	iterator (CSVReader *, CSVRow &&)
CONSTEXPR_14 reference	operator* ()
	Access the CSVRow held by the iterator.
CONSTEXPR_14 reference	operator* () const
CONSTEXPR_14 pointer	operator-> ()
	Return a pointer to the CSVRow the iterator has stopped at.
CONSTEXPR_14 pointer	operator-> () const
iterator &	operator++ ()
	Pre-increment iterator.
iterator	operator++ (int)
	Post-increment iterator.
CONSTEXPR bool	operator== (const iterator &other) const noexcept
	Returns true if iterators were constructed from the same CSVReader and point to the same row.
CONSTEXPR bool	operator!= (const iterator &other) const noexcept

Detailed Description

An input iterator capable of handling large files.

Note

Created by CSVReader::begin() and CSVReader::end().

Iterating over a file

#ifndef __EMSCRIPTEN__
TEST_CASE("Basic CSVReader Iterator Test", "[read_ints_iter]") {
    // A file with 100 rows and columns A, B, ... J
    // where every value in the ith row is the number i
    CSVReader reader("./tests/data/fake_data/ints.csv");
    std::vector<std::string> col_names = {
        "A", "B", "C", "D", "E", "F", "G", "H", "I", "J"
    };
    int i = 1;
 
    SECTION("Basic Iterator") {
        for (auto it = reader.begin(); it != reader.end(); ++it) {
            REQUIRE((*it)[0].get<int>() == i);
            i++;
        }
    }
 
    SECTION("Iterator Post-Increment") {
        auto it = reader.begin();
        REQUIRE((it++)->operator[]("A").get<int>() == 1);
        REQUIRE(it->operator[]("A").get<int>() == 2);
    }
 
    SECTION("Range-Based For Loop") {
        for (auto& row : reader) {
            for (auto& j : col_names) REQUIRE(row[j].get<int>() == i);
            i++;
        }
    }
}
#endif

Using with <algorithm> library

 
#ifndef __EMSCRIPTEN__
TEST_CASE("CSVReader Iterator + Algorithms Requiring ForwardIterator", "[iter_algorithms]") {
    SECTION("std::max_element - CORRECT approach using vector") {
        // The first is such that each value in the ith row is the number i
        // There are 100 rows
        CSVReader reader("./tests/data/fake_data/ints.csv");
 
        // Copy rows to vector to enable ForwardIterator algorithms
        auto rows = std::vector<CSVRow>(reader.begin(), reader.end());
        REQUIRE(rows.size() == 100);
 
        // Find largest number
        auto int_finder = [](const CSVRow& left, const CSVRow& right) {
            return (left["A"].get<int>() < right["A"].get<int>());
        };
 
        auto max_int = std::max_element(rows.begin(), rows.end(), int_finder);
        REQUIRE((*max_int)["A"] == 100);
    }
 
    SECTION("std::max_element - Large File using vector") {
        // The second file is a database of California state employee salaries
        CSVReader reader("./tests/data/real_data/2015_StateDepartment.csv");
        
        // Copy rows to vector to enable ForwardIterator algorithms
        auto rows = std::vector<CSVRow>(reader.begin(), reader.end());
        
        // Find highest salary
        auto wage_finder = [](const CSVRow& left, const CSVRow& right) {
            return (left["Total Wages"].get<double>() < right["Total Wages"].get<double>());
        };
 
        auto max_wage = std::max_element(rows.begin(), rows.end(), wage_finder);
 
        REQUIRE((*max_wage)["Total Wages"] == "812064.87");
    }
}
#endif

Note

This iterator is std::input_iterator_tag (single-pass) by design. Algorithms requiring ForwardIterator are not safe to use directly on it. Copy to std::vector<CSVRow> first when random-access algorithms are needed. See include/internal/ARCHITECTURE.md § "CSVReader::iterator is single-pass by design" for the full rationale.

Definition at line 79 of file csv_reader.hpp.

Constructor & Destructor Documentation

iterator() [1/2]

csv::CSVReader::iterator::iterator ( CSVReader *  reader )

inline

Definition at line 90 of file csv_reader.hpp.

iterator() [2/2]

csv::CSVReader::iterator::iterator	(	CSVReader *	_daddy,
		CSVRow &&	_row
	)

Definition at line 24 of file csv_reader_iterator.cpp.

Member Function Documentation

operator!=()

CONSTEXPR bool csv::CSVReader::iterator::operator!= ( const iterator &  other ) const

inlinenoexcept

Definition at line 111 of file csv_reader.hpp.

operator*() [1/2]

CONSTEXPR_14 reference csv::CSVReader::iterator::operator* ( )

inline

Access the CSVRow held by the iterator.

Definition at line 94 of file csv_reader.hpp.

operator*() [2/2]

CONSTEXPR_14 reference csv::CSVReader::iterator::operator* ( ) const

inline

Definition at line 95 of file csv_reader.hpp.

operator++() [1/2]

CSVReader::iterator & csv::CSVReader::iterator::operator++

(

)

Pre-increment iterator.

Advance the iterator by one row.

If this CSVReader has an associated file, then the iterator will lazily pull more data from that file until the end of file is reached.

Note

This iterator does not block the thread responsible for parsing CSV.

Definition at line 36 of file csv_reader_iterator.cpp.

operator++() [2/2]

CSVReader::iterator csv::CSVReader::iterator::operator++

(

int

)

Post-increment iterator.

Definition at line 45 of file csv_reader_iterator.cpp.

operator->() [1/2]

CONSTEXPR_14 pointer csv::CSVReader::iterator::operator-> ( )

inline

Return a pointer to the CSVRow the iterator has stopped at.

Definition at line 98 of file csv_reader.hpp.

operator->() [2/2]

CONSTEXPR_14 pointer csv::CSVReader::iterator::operator-> ( ) const

inline

Definition at line 99 of file csv_reader.hpp.

operator==()

CONSTEXPR bool csv::CSVReader::iterator::operator== ( const iterator &  other ) const

inlinenoexcept

Returns true if iterators were constructed from the same CSVReader and point to the same row.

Definition at line 107 of file csv_reader.hpp.

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

• include/internal/csv_reader.hpp
• include/internal/csv_reader_iterator.cpp