Why do I get the error "Callout from scheduled Apex not supported"?

Question

I have scheduled the execution of my class and am getting an error. What did I do wrong and how do I fix it?

global class SchedulableExchangeRate implements Schedulable {
    global void execute(SchedulableContext ctx){
        CurrencyExchangeController newCurExcContr = new CurrencyExchangeController();
        newCurExcContr.calloutCurrency();
    }
}


public class CurrencyExchangeController {
    public void calloutCurrency(){
    //here is the code of my method
    }
}

Answer 1

You're not allowed to make a callout from a Scheduled job. To fix this, call a future or queueable from the scheduled job.

global class SchedulableExchangeRate implements Schedulable {
    global void execute(SchedulableContext ctx){
        CurrencyExchangeController.calloutCurrency();
    }
}


public class CurrencyExchangeController {
    @future(callout=true) public static void calloutCurrency(){
    //here is the code of my method
    }
}

Note the change to a static method, and (callout=true). Note also you're limited to just one @future method in a schedulable execution.