boost::urls::grammar::variant_rule

Match one of a set of rules

Synopsis

Declared in <include/boost/url/grammar/variant_rule.hpp>

template<
    Rule R0,
    Rule…​ Rn>
constexpr
/* implementation-defined */
variant_rule(
    R0 const& r0,
    Rn const&…​ rn) noexcept;
cpp

Description

Each specified rule is tried in sequence. When the first match occurs, the result is stored and returned in the variant. If no match occurs, an error is returned.

using value_type = variant< typename Rules::value_type... >;
cpp

Example

Rules are used with the function parse.

// request-target = origin-form
//                / absolute-form
//                / authority-form
//                / asterisk-form

system::result< variant< url_view, url_view, authority_view, core::string_view > > rv = grammar::parse(
    "/index.html?width=full",
    variant_rule(
        origin_form_rule,
        absolute_uri_rule,
        authority_rule,
        delim_rule('*') ) );
cpp
variant     = rule1 / rule2 / rule3...
cpp

See Also

absolute_uri_rule, authority_rule, delim_rule, parse, origin_form_rule, url_view.

Created with MrDocs