= cowboy_stream:init(3)

== Name

cowboy_stream:init - Initialize a stream

== Description

[source,erlang]
----
init(StreamID, Req, Opts) -> {Commands, State}

StreamID :: cowboy_stream:stream_id()
Req      :: cowboy_req:req()
Opts     :: cowboy:opts()
Commands :: cowboy_stream:commands()
State    - opaque
----

Initialize a stream.

This function must be called by all stream handlers. It will
initialize the next configured stream handler.

== Arguments

StreamID::

The stream ID.

Req::

The Req object.

Opts::

The protocol options.

Commands::

The commands to be executed.

State::

The state for the next stream handler.

== Return value

A list of commands and an opaque state is returned.

The list of commands returned should be included in the
commands returned from the current stream handler. It
can be modified if necessary.

The state should be stored in the current stream
handler's state and passed to `cowboy_stream` when
necessary. The state should be treated as opaque.

== Changelog

* *2.0*: Function introduced.

== Examples

.Initialize the next stream handler
[source,erlang]
----
init(StreamID, Req, Opts) ->
    MyCommands = my_commands(),
    {Commands, Next} = cowboy_stream:init(StreamID, Req, Opts),
    {MyCommands ++ Commands, #state{next=Next}}.
----

== See also

link:man:cowboy_stream(3)[cowboy_stream(3)],
link:man:cowboy_stream:data(3)[cowboy_stream:data(3)],
link:man:cowboy_stream:info(3)[cowboy_stream:info(3)],
link:man:cowboy_stream:terminate(3)[cowboy_stream:terminate(3)],
link:man:cowboy_stream:early_error(3)[cowboy_stream:early_error(3)]