sharg::validator Concept Reference

The concept for option validators passed to add_option/positional_option. More...

#include <sharg/validators.hpp>

Concept definition

template<typename validator_type>
concept sharg::validator =  std::copyable<std::remove_cvref_t<validator_type>> &&
                    requires { typename std::remove_reference_t<validator_type>::option_value_type; } &&
                    requires(validator_type validator,
                             typename std::remove_reference_t<validator_type>::option_value_type value)
                    {
                        {validator(value)} -> std::same_as<void>;
                        {validator.get_help_page_message()} -> std::same_as<std::string>;
                    }

Detailed Description

The concept for option validators passed to add_option/positional_option.

When adding (positional) options to the sharg::parser you may pass a function object that models sharg::validator which checks the option value provided by the user for some constraint.

Sharg provides several common-use-case validators, e.g. the sharg::arithmetic_range_validator.

#include <sharg/all.hpp>
 
int main(int argc, char const ** argv)
{
    sharg::parser myparser{"Test", argc, argv}; // initialize
 
    int myint;
    sharg::value_list_validator my_validator{2, 4, 6, 8, 10};
 
    myparser.add_option(myint,
                        sharg::config{.short_id = 'i',
                                      .long_id = "integer",
                                      .description = "Give me a number.",
                                      .validator = my_validator});
 
    // an exception will be thrown if the user specifies an integer
    // that is not one of [2,4,6,8,10] (e.g. "./test_app -i 3")
    try
    {
        myparser.parse();
    }
    catch (sharg::parser_error const & ext) // the user did something wrong
    {
        std::cerr << "[PARSER ERROR] " << ext.what() << "\n"; // customize your error message
        return -1;
    }
 
    std::cerr << "integer given by user passed validation: " << myint << "\n";
    return 0;
}

You can learn more about Sharg validators in our tutorial Validation of (positional) option values.

To implement your own validator please refer to the detailed concept description below.

This entity is stable. Since version 1.0.