How to check if future method has executed

Question

in my apex code I need to do some calculation only when future method has executed I tried below code to check if future method has executed:

public static void anotherMethod() {
while('Completed' != checkFutureMethod()) {
            checkFutureMethod();
         }

// need to do something here only when future method has executed
}

 private static string checkFutureMethod() {
        string asyncApexStatus;
        for(AsyncApexJob asyncApex : [select Status From AsyncApexJob where ApexClass.Name = 'classname']) {
                                 asyncApexStatus = asyncApex.Status; 
                              }
        return asyncApexStatus;

    }

but still the above doesn't wait future method to finish, please suggest.

Answer 1

First, asynchronous methods will never even start until the previous transaction commits, so any wait loop would need to be asynchronous itself. Secondly, if you need the status of an asynchronous call, use Queueable instead. Unlike future methods, Queueable methods provide a JobId, which you can query against to see if the unit has executed, and if it did so successfully.

MyQueueable someQueueable = new MyQueueable();
Id jobId = System.enqueueJob(someQueueable);

// ... some time later ... //
AsyncApexJob job = [SELECT Status FROM AsyncApexJob WHERE Id = :jobId];

Remember, you must allow the current transaction to complete before the asynchronous code can run, so you'll need a mechanism to wait, such as using a Visualforce page with apex:actionPoller.

Presumably, your code will find the first future method ever to be called by that class, thus will immediately return as completed. There's no way to determine which future method is which with 100% accuracy, which is one reason why Queueable was invented.