std::string contains() method

od C++23

// (1) Const version only
constexpr bool contains( std::basic_string_view<CharT,Traits> sv ) const noexcept;

// (2) Const version only
constexpr bool contains( CharT c ) const noexcept;

// (3) Const version only
constexpr bool contains( const CharT* s ) const;

Checks if the string contains the given substring

The prefix may be one of the following:

• (1) A string view sv (which may be a result of implicit conversion from another std::basic_string).

• (2) A single character c.

• (3) A null-terminated character string s.

All three overloads effectively do

find(x) != npos;

where x is the parameter.

Parameters

• s - a string view which may be a result of implicit conversion from another std::basic_string
• c - a single character
• s - a null-terminated character string

Return value

true if the string contains the provided substring, false otherwise.

Complexity

important

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Notes

Feature testing macro: __cpp_lib_string_contains.

Example

#include <iomanip>
#include <iostream>
#include <string>
#include <string_view>
#include <type_traits>
 
template <typename SubstrType>
void test_substring(const std::string& str, SubstrType subs)
{
    constexpr char delim = std::is_scalar_v<SubstrType> ? '\'' : '\"';
    std::cout << std::quoted(str)
              << (str.contains(subs) ? " contains "
                                     : " does not contain ")
              << std::quoted(std::string{subs}, delim) << '\n';
}
 
int main()
{
    using namespace std::literals;
 
    auto helloWorld = "hello world"s;
 
    test_substring(helloWorld, "hello"sv);
    test_substring(helloWorld, "goodbye"sv);
    test_substring(helloWorld, 'w');
    test_substring(helloWorld, 'x');
}

Output

"hello world" contains "hello"
"hello world" does not contain "goodbye"
"hello world" contains 'w'
"hello world" does not contain 'x'