Class request_attributes

boost::taar::request_attributes — A small type-indexed bag of values attached to one request.

Synopsis

// In header: <boost/taar/core/request_attributes.hpp>


class request_attributes {
public:

  // public member functions
  template<typename T> void set(T);
  template<typename T> T * find() noexcept;
  template<typename T> T const * find() const noexcept;
  template<typename T> bool contains() const noexcept;
  bool empty() const noexcept;
};

Description

Carried by boost::taar::matcher::context::attributes, so whatever an interceptor or a handler::guard check stores is visible to the handler that later runs on the same request, and to argument providers such as handler::attribute_arg<T>(). At most one value is kept per type: storing a second value of the same type replaces the first. Define a dedicated type (struct principal { std::string user; };) rather than storing a bare std::string, so that unrelated code does not collide on the key.

Values must be copy-constructible (they are held in a std::any). An empty bag allocates nothing.

struct principal { std::string user; };

ctx.attributes.set(principal {"alice"});
if (auto const* p = ctx.attributes.find<principal>())
    use(p->user);

`request_attributes` public member functions

```
template<typename T> void set(T value);
```
Store value under its type T, replacing any value of that type.
```
template<typename T> T * find() noexcept;
```
The stored value of type T, or nullptr if there is none.

template<typename T> T const * find() const noexcept;

The stored value of type T, or nullptr if there is none.

template<typename T> bool contains() const noexcept;

True if a value of type T is stored.

```
bool empty() const noexcept;
```
True if no value is stored.