## Class template mutable_constant<T, void, void, void>

boost::log::attributes::mutable_constant<T, void, void, void> — Specialization for unlocked case.

## Synopsis

    // In header: <boost/log/attributes/mutable_constant.hpp>

    template<typename T>
    class mutable_constant<T, void, void, void> : public attribute {
    public:
      // types
      typedef T value_type;  // The attribute value type.

      // member classes/structs/unions

      // Factory implementation.

      class impl : public attribute::impl {
      public:
        // construct/copy/destruct
        explicit impl(value_type const &);
        explicit impl(value_type &&);

        // public member functions
        virtual attribute_value get_value();
        void set(value_type const &);
        void set(value_type &&);
        value_type get() const;
      };

      // construct/copy/destruct
      explicit mutable_constant(value_type const &);
      explicit mutable_constant(value_type &&);
      explicit mutable_constant(cast_source const &);

      // public member functions
      void set(value_type const &);
      void set(value_type &&);
      value_type get() const;

      // protected member functions
      impl * get_impl() const;
    };

## Description

This version of attribute does not perform thread synchronization to access the stored value.

### `mutable_constant` public construct/copy/destruct

1.     explicit mutable_constant(value_type const & value);

   Constructor with the stored value initialization

2.     explicit mutable_constant(value_type && value);

   Constructor with the stored value initialization

3.     explicit mutable_constant(cast_source const & source);

   Constructor for casting support

### `mutable_constant` public member functions

1.     void set(value_type const & value);

   The method sets a new attribute value.

2.     void set(value_type && value);

   The method sets a new attribute value.

3.     value_type get() const;

   The method acquires the current attribute value.

### `mutable_constant` protected member functions

1.     impl * get_impl() const;

   Returns: | Pointer to the factory implementation