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Added eval function for both strings and expressions.

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eval wraps whatever you give to it into a select call, sends it to the
database and returns the value as a result field.
This commit is contained in:
rbock
2014-08-18 10:46:24 +02:00
parent f6ae27b0fe
commit d0d5e94bf1
4 changed files with 141 additions and 40 deletions
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62
include/sqlpp11/eval.h Normal file
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@@ -0,0 +1,62 @@
/*
* Copyright (c) 2013-2014, Roland Bock
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice, this
* list of conditions and the following disclaimer in the documentation and/or
* other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SQLPP_EVAL_H
#define SQLPP_EVAL_H
#include <sqlpp11/type_traits.h>
#include <sqlpp11/field_spec.h>
#include <sqlpp11/alias_provider.h>
#include <sqlpp11/verbatim.h>
namespace sqlpp
{
template<typename Db, typename Expr>
struct eval_t
{
static_assert(is_database<Db>::value, "Db parameter of eval has to be a database connection");
static_assert(is_expression_t<Expr>::value, "Expression parameter of eval has to be an sqlpp expression or a string");
static_assert(required_tables_of<Expr>::size::value == 0, "Expression cannot be used in eval because it requires tables");
using _name_type = alias::a_t::_name_t;
using _value_type = value_type_of<Expr>;
using _field_spec = field_spec_t<_name_type, _value_type, true, false>;
using type = result_field_t<_value_type, Db, _field_spec>;
};
template<typename Db, typename Expr, typename std::enable_if<not std::is_convertible<Expr, std::string>::value, int>::type = 0>
auto eval(Db& db, Expr expr) -> typename eval_t<Db, Expr>::type
{
return db(select(expr.as(alias::a))).front().a;
}
template<typename ValueType, typename Db>
auto eval(Db& db, std::string sql_code) -> decltype(eval(db, verbatim<ValueType>(sql_code)))
{
return eval(db, verbatim<ValueType>(sql_code));
}
}
#endif

42
include/sqlpp11/functions.h
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@@ -41,8 +41,10 @@
#include <sqlpp11/max.h>
#include <sqlpp11/avg.h>
#include <sqlpp11/sum.h>
#include <sqlpp11/verbatim_table.h> // Csaba Csoma suggests: unsafe_sql instead of verbatim
#include <sqlpp11/verbatim.h> // Csaba Csoma suggests: unsafe_sql instead of verbatim
#include <sqlpp11/verbatim_table.h>
#include <sqlpp11/value_or_null.h>
#include <sqlpp11/eval.h>
namespace sqlpp
{
@@ -53,44 +55,6 @@ namespace sqlpp
return { t };
}
template<typename ValueType> // Csaba Csoma suggests: unsafe_sql instead of verbatim
struct verbatim_t: public ValueType::template expression_operators<verbatim_t<ValueType>>,
public alias_operators<verbatim_t<ValueType>>
{
using _traits = make_traits<ValueType, ::sqlpp::tag::is_expression>;
struct _recursive_traits : public make_recursive_traits<>
{
using _can_be_null = std::true_type; // since we do not know what's going on inside the verbatim, we assume it can be null
};
verbatim_t(std::string verbatim): _verbatim(verbatim) {}
verbatim_t(const verbatim_t&) = default;
verbatim_t(verbatim_t&&) = default;
verbatim_t& operator=(const verbatim_t&) = default;
verbatim_t& operator=(verbatim_t&&) = default;
~verbatim_t() = default;
std::string _verbatim;
};
template<typename Context, typename ValueType>
struct serializer_t<Context, verbatim_t<ValueType>>
{
using T = verbatim_t<ValueType>;
static Context& _(const T& t, Context& context)
{
context << t._verbatim;
return context;
}
};
template<typename ValueType, typename StringType>
auto verbatim(StringType s) -> verbatim_t<ValueType>
{
return { s };
}
template<typename Expression, typename Db>
auto flatten(const Expression& exp, Db& db) -> verbatim_t<value_type_of<Expression>>
{

2
include/sqlpp11/result_field.h
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@@ -32,7 +32,7 @@
namespace sqlpp
{
template<typename ValueType, typename Db, typename Field>
template<typename ValueType, typename Db, typename FieldSpec>
struct result_field_t
{
static_assert(wrong_t<result_field_t>::value, "Missing specialization for result_field_t");

75
include/sqlpp11/verbatim.h Normal file
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@@ -0,0 +1,75 @@
/*
* Copyright (c) 2013-2014, Roland Bock
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice, this
* list of conditions and the following disclaimer in the documentation and/or
* other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SQLPP_VERBATIM_H
#define SQLPP_VERBATIM_H
#include <sqlpp11/type_traits.h>
#include <sqlpp11/serialize.h>
namespace sqlpp
{
template<typename ValueType> // Csaba Csoma suggests: unsafe_sql instead of verbatim
struct verbatim_t: public ValueType::template expression_operators<verbatim_t<ValueType>>,
public alias_operators<verbatim_t<ValueType>>
{
using _traits = make_traits<ValueType, ::sqlpp::tag::is_expression>;
struct _recursive_traits : public make_recursive_traits<>
{
using _can_be_null = std::true_type; // since we do not know what's going on inside the verbatim, we assume it can be null
};
verbatim_t(std::string verbatim): _verbatim(verbatim) {}
verbatim_t(const verbatim_t&) = default;
verbatim_t(verbatim_t&&) = default;
verbatim_t& operator=(const verbatim_t&) = default;
verbatim_t& operator=(verbatim_t&&) = default;
~verbatim_t() = default;
std::string _verbatim;
};
template<typename Context, typename ValueType>
struct serializer_t<Context, verbatim_t<ValueType>>
{
using T = verbatim_t<ValueType>;
static Context& _(const T& t, Context& context)
{
context << t._verbatim;
return context;
}
};
template<typename ValueType, typename StringType>
auto verbatim(StringType s) -> verbatim_t<ValueType>
{
return { s };
}
}
#endif