std::basic_string_view<CharT,Traits>::at

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

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Filesystem library (C++17)

Technical Specifications

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

std::basic_string_view

Member functions basic_string_view::basic_string_view basic_string_view::operator= Iterators basic_string_view::beginbasic_string_view::cbegin basic_string_view::endbasic_string_view::cend basic_string_view::rbeginbasic_string_view::crbegin basic_string_view::rendbasic_string_view::crend Element access basic_string_view::at basic_string_view::operator[] basic_string_view::front basic_string_view::back basic_string_view::data Capacity basic_string_view::sizebasic_string_view::length basic_string_view::max_size basic_string_view::empty Modifiers basic_string_view::remove_prefix basic_string_view::remove_suffix basic_string_view::swap

Operations basic_string_view::copy basic_string_view::substr basic_string_view::compare basic_string_view::starts_with (C++20) basic_string_view::ends_with (C++20) basic_string_view::find basic_string_view::rfind basic_string_view::find_first_of basic_string_view::find_last_of basic_string_view::find_first_not_of basic_string_view::find_last_not_of Constants basic_string_view::npos Non-member functions operator==operator!=operator<operator>operator<=operator>= operator<< operator""sv Helper classes hash<std::string_view>hash<std::wstring_view>hash<std::u16string_view>hash<std::u32string_view>

 

constexpr const_reference at(size_type pos) const;		(since C++17)

Returns a reference to the character at specified location pos. Bounds checking is performed, exception of type std::out_of_range will be thrown on invalid access.

Parameters

pos

-

position of the character to return

Return value

Reference to the requested character.

Exceptions

Throws std::out_of_range if pos >= size().

Complexity

Constant.

Example

Run this code

#include <iostream>
#include <stdexcept>
#include <string_view>
 
int main()
{
    std::string_view str_view("abcdef");
 
    try {
        for (std::size_t i = 0; true; ++i)
            std::cout << i << ": " << str_view.at(i) << '\n';
    }
    catch (const std::out_of_range& e) {
        std::cout << "Whooops. Index is out of range.\n";
        std::cout << e.what() << '\n';
    }
}

Possible output:

0: a
1: b
2: c
3: d
4: e
5: f
6: Whooops. Index is out of range.
basic_string_view::at: __pos (which is 6) >= this->size() (which is 6)

See also

operator[]

accesses the specified character (public member function)