Occasionally I forget that joining to arrays is not the same as appending and array to an array which leads to some real funky results.

Of course ColdFusion does not have a real cute method to join to arrays, but never fear, Java does!

I will use the following as an example. I am trying to create an abstract method called hasRegistration() to return an array of registrations. The method accepts any argument, but will only process an object or struct. The method uses one of two other methods (which all we need to know right now is that they return an array), either hasRegistrationObj() or hasRegistrationStruct(). Returning an empty array is totally acceptable in any case. Here is how I would use the Java method to join to arrays.

/**
 * @returnType array
 * @hint "return array of registrations"
*/
public function hasRegistration( required any rc ) {
    registration = [];
    if( isObject(arguments.rc) ) {
        registration.addAll(hasRegistrationObj(arguments.rc));
    }
    else {
        registration.addAll(hasRegistrationStruct(arguments.rc));
    }
    return registration;
}

That should do it. If the argument passed is neither an object or struct we return an empty array. Otherwise we join the array returned from one of the other two methods.