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/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma once
#include <string>
namespace dev
{
/// Simple generic result that holds a value and an optional error message.
/// Results can be implicitly converted to and created from the type of
/// the value they hold.
///
/// Result<bool> check()
/// {
/// if (false)
/// return Result<bool>(false, "Error message.")
/// return true;
/// }
///
/// A result can also be instantiated using one of the factory methods it provides:
///
/// using BoolResult = Result<bool>;
/// BoolResult check()
/// {
/// if (false)
/// return BoolResult::failure("Error message");
/// return BoolResult::success(true);
/// }
///
///
struct ResultError { std::string reason; };
template <class ResultType>
class Result
{
public:
/// @{
/// @name Factory functions
/// Factory functions that provide a verbose way to create a result
static Result<ResultType> Ok(ResultType _value) { return Result(std::move(_value)); }
static Result<ResultType> Err() { return Result(ResultError{std::string()}); }
static Result<ResultType> Err(std::string _error) { return Result(ResultError{std::move(_error)}); }
/// @}
Result(ResultType _value): m_value(std::move(_value)) {}
Result(ResultError _error): m_error(std::move(_error.reason)) {}
Result(ResultType _value, ResultError _error): m_value(std::move(_value)), m_error(std::move(_error.reason)) {}
/// @{
/// @name Wrapper functions
/// Wrapper functions that provide implicit conversions to and explicit retrieval of
/// the value this result holds.
/// If the result is an error, accessing the value results in undefined behaviour.
operator ResultType const&() const { return m_value; }
ResultType& operator*() const { return m_value; }
ResultType const& get() const { return m_value; }
ResultType& get() { return m_value; }
/// @}
/// @returns the error message (can be empty).
std::string const& err() const { return m_error; }
private:
ResultType m_value;
std::string m_error;
};
}
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