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Send messages

In this tutorial we will show how to react to messages send by the system.

At runtime a channel component is defined to send messages.

Define the message

After creating a system:

• click on the import button on the left toolbar,
• a dialog is shown,
• click on from the library radio button,
• select Send messages through a channel from the proposed systems,
• click on the Compose button,

This system has now been composed in your system.

• on Schemas tab, click on _Channel schema (on the right panel under Schemas),

• click on _Channel schema to edit it,
• add somethingHappened event:

{
  "_id": "104ad1f48518376",
  "_name": "_Channel",
  "_inherit": [
    "_Component"
  ],
  "send": "event",
  "somethingHappened": "event"
}

• on Models tab, click on _Channel model (on the right panel under Models),

• click on _Channel model,
• edit with this code:

{
  "_id": "135c71078810af2",
  "_name": "_Channel",
  "send": {
    "params": [
      {
        "name": "message",
        "type": "message"
      }
    ]
  },
  "somethingHappened": {
    "description": "",
    "params": [
      {
        "description": "",
        "name": "param",
        "type": "string",
        "mandatory": false,
        "default": ""
      }
    ]
  }
}

Define the listener

Now we will create the listener to that message:

• on Behaviors tab, click on _Channel model (on the right panel under Models),
• then click on channel component (on the right panel under Components),
• click on the '+' button on the left toolbar to add a behavior,
• select somethingHappened from the list,
• click on the Create button

• click on the somethingHappened behavior,
• add this code:

function somethingHappened(param) { 
  // get logger component
  let logger = this.require('logger');

  logger.info('the message "' + param + '" has been send.');
}

Send the message

• on Behavior tab, select your system (on the right panel under System),
• click on start behavior,
• add this code:

function start() { 
  this.require('channel').somethingHappened('my message');  
}

• run your system

• you will see a message on the bottom right of System Designer and a new log on the Logs tab.