value_or.hpp

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/*
    restinio
*/
 
/*!
    Helper functions for parameter extraction with default values.
 
    @since v.0.4.4
*/
 
#pragma once
 
#include <type_traits>
 
#include <restinio/cast_to.hpp>
#include <restinio/uri_helpers.hpp>
#include <restinio/router/express.hpp>
 
namespace restinio
{
 
//! Get parameter value or a given default.
/*!
    Get the value of a parameter specified by \a key if parameter exists.
    If parameter exists in \a params it is obtained as \c string_view_t object and
    casted to a necessary type and then returns.
    If \a params has no such parameters then the \a default_value is returned.
 
    @since v.0.4.4
*/
template < typename Value_Type, typename Parameter_Container >
typename std::enable_if<
        std::is_same< Parameter_Container, query_string_params_t >::value ||
            std::is_same< Parameter_Container, router::route_params_t >::value,
        Value_Type >::type
value_or( const Parameter_Container & params, string_view_t key, Value_Type default_value )
{
    const auto value = params.get_param( key );
    if( value )
    {
        return cast_to< Value_Type >( *value );
    }
 
    return default_value;
}
 
/*!
    \brief Gets the value of a parameter specified by \a key wrapped in `std::optional<Value_Type>`
    if parameter exists and empty `std::optional<Value_Type>`
    if parameter with a given key value doesn't exist.
 
    If parameter exists in \a params it is obtained as \c string_view_t object and
    casted to a necessary type and then is wrapped in `std::optional<Value_Type>`.
    If \a params has no such parameters then the empty `std::optional<Value_Type>`
    is returned.
 
    @since v.0.4.5.1
*/
template < typename Value_Type, typename Parameter_Container >
typename std::enable_if<
        std::is_same< Parameter_Container, query_string_params_t >::value ||
            std::is_same< Parameter_Container, router::route_params_t >::value,
        std::optional< Value_Type > >::type
opt_value( const Parameter_Container & params, string_view_t key )
{
    std::optional< Value_Type > result{};
 
    const auto value = params.get_param( key );
    if( value )
    {
        result = cast_to< Value_Type >( *value );
    }
 
    return result;
}
 
} /* namespace restinio */