|purchase_id||This can either be the Apple Store/Google Play id string, an URL id, or an index into the available purchases ds_list.|
WARNING! This function has been deprecated.
This function can be used for checking to see if a purchase has been downloaded correctly (returns true) or not (returns false). The purchase_id can be either an integer index into the main purchases list, the explicit Apple Store/Google Play id string, or you can pass through the actual identifier name(eg: ".extralevels"), similar to the way that iap_acquire works. Please note that for consumables (ie: purchases that require no downloadable content) this function will always return true.
We can use this function to check and see if the paid-for purchase has finished downloading or not. To start with we need to check the data returned from the function iap_event_queue which you would get from the asynchronous IAP Event. In the Create Event of the instance you would prepare a variable to store the returned value of this function and then in the IAP event itself have something like this:
q = iap_event_queue();
downloaded = ds_queue_dequeue(q);
downloaded = 0;
We can then use this value in other IAP functions, or simply check it to draw a status message for our user to see so they know that the download has been completed:
draw_text(x, y, "Files downloaded:");
The above code will now use the iap_is_downloaded function to display a message to the user when the product they have bought has been downloaded correctly.