how to send trigger data to future method and change it based on response from callout

Question

My triger code is

trigger sendMessage on Message__c (before insert) {
    //retrieve contact info of selected contact--------------------
    sObject contact = [Select Name, Phone, Title, MobilePhone from Contact WHERE Id =:Trigger.new[0].Contact_Mobile__c];

    String data = '{"contactInfo":'+JSON.serialize(contact)+',"message":"'+Trigger.new[0].Text_Message__c+'"}';    

    //sendMessageOnTrigger sendMessage = new sendMessageOnTrigger();
    sendMessageOnTrigger.sendMessage(data);

}

My class code which contains future method

public with sharing class sendMessageOnTrigger {

    @future(callout=true)
    public static void sendMessage(String data){              

        Http http = new Http();
        HttpRequest request = new HttpRequest();
        request.setEndpoint('http://twil-smsapp.herokuapp.com/api/sendSms');
        request.setMethod('POST');
        request.setHeader('Content-Type', 'application/json;charset=UTF-8');
        // Set the body as a JSON object
        request.setBody(data);
        HttpResponse response = http.send(request);
        System.debug('-------------------------------------->');                
        // Parse the JSON response
        if (response.getStatusCode() != 200) {
            System.debug('The status code returned was not expected: ' +
                response.getStatusCode() + ' ' + response.getStatus());
            //Trigger.new[0].Text_Message__c.addError('Unable to send message!!, please try again later.');
            //ApexPages.AddMessage(new ApexPages.Message(ApexPages.Severity.ERROR,'Oops, something went wrong!!'));
        } else {
            //ApexPages.AddMessage(new ApexPages.Message(ApexPages.Severity.CONFIRM,'Message sent successfully!'));
            System.debug(response.getBody());
            Map<String, Object> json =
                (Map<String, Object>)
                    JSON.deserializeUntyped(response.getBody());
            if(json.get('responseCode') != 200) {
                //change trigger data here if response is not expected so that insert operation will stop and generate an errror
    //Trigger.new[0].Text_Message__c.addError('Unable to send message!!, please try again later.');
            } 
        }
        System.debug('<--------------------------------------');
    }
}

I want to modify the trigger data in future method which has a http request to stop the insert operation if the api http request is not correct. For that, I will be using Trigger.new[0].Text_Message__c.addError('Unable to send message!!, please try again later.');. How can we achieve this?

Answer 1

You cannot, in your trigger, surface errors that take place in a future method, because the future method executes in a different transaction. There's no way to communicate back to the trigger from that context.

However, your future method can modify the Message__c objects - its changes just won't propagate back to the trigger. If you are initiating these message sends from a Visualforce or Lightning page, your page can poll the inserted objects for a status message you write there.

That said, I am skeptical of the design here. If, again, you are initiating the sending of these messages from a user interface, why not make the callouts from the UI controller side? You can then handle any errors appropriately before writing an object into the database, if you need to do so.