etl/docs/Messaging/messages.md

title
Messages

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Message types used for many of the framework classes.

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etl::message_id_t

The type used for message ids.
By default can hold a value between 0 and 255.
If ETL_MESSAGE_ID_TYPE is defined then this type will be used instead.

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etl::message_router_id_t

The type used for message router ids.
Can hold a value between 0 and 255.

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The message classes are the common communication method across all of the message capable frameworks. They are identified by a unique id number that specialises the base class.

imessage

The base class for messages. It is this class that is passed around, usually by const reference.
The class is abstract.

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etl::message_id_t get_message_id() const ETL_NOEXCEPT = 0;

Returns the id of the message.

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message

message<size_t ID, typename TParent = etl::imessage>

Requires an integral id as the template parameter.
Inherits from TParent, which defaults to etl::imessage.
TParent allows additional base interfaces or functionality to be included.
static asserts if TParent is not a base of etl::imessage.

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ID

The id of the message as an enum. Can be accessed by etl::message instances.

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TParent

The class that it inherits from. It must ultimately derive from etl::imessage.
The default is etl::imessage.

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Example

enum
{
  START,
  STOP,
  SET_SPEED
};

struct MyInterface : public etl::imessage
{
  virtual void DoStuff() = 0;
};

// Start implements MyIterface
struct Start : public etl::message<START, MyInterface>
{
  void DoStuff() override
  {
    // Do stuff here.  
  }
};

struct Stop : public etl::message<STOP>
{
  bool isEmergencyStop;
};

struct SetSpeed : public etl::message<SET_SPEED>
{
  uint32_t speed;
};

void Receive(const etl::imessage& msg);