#### io_context::dispatch

(Deprecated: Use `dispatch`.) Request the `io_context` to invoke the given handler.

    template<
        typename LegacyCompletionHandler>
    auto dispatch(
        LegacyCompletionHandler && handler);

This function is used to ask the `io_context` to execute the given handler.

The `io_context` guarantees that the handler will only be called in a thread in which the `run()`, `run_one()`, `poll()` or `poll_one()` member functions is currently being invoked. The handler may be executed inside this function if the guarantee can be met.

###### Parameters

handler

  The handler to be called. The `io_context` will make a copy of the handler object as required. The function signature of the handler must be:

      void handler();

###### Remarks

This function throws an exception only if:

- the handler's associated allocator; or
- the handler's copy constructor

throws an exception.