ma We have used saved games in a few of our games for this exact purpose, to track a level of "coins" that the user can spend in app, and we have a few iap that allows a user to purchase more. It works really well.
Thanks for the comments. I'm going to be adding in your game services extension for google play leader boards/achievements so it seems logical to use saved games for this as well.
ma user's who don't sign into game services
I don't see a clear solution for this. I'll probably take a hit, but as of right now I'm planning on requiring the end user to sign in to game services before they can play the game.
This is the general initialization flow that I'm considering......
1) Have an initial sign in screen at start up, "Initializing Game Services", etc, etc..
2) During this period initialize google play services, sign in, etc.
3) Assuming services initialization, sign in, was ok, then proceed with loading virtual coins, otherwise after a period of time display a message to the end user services could not connect, please try again, etc, etc.
4) Now we're logged in, so I need a way to check and set up the default number of free coins for each new user. I've never used the gp services saved games, but I'm guessing if I try to retrieve data for saved coins and it's not there I should at that point create a saved games data for the default number of coins and save them immediately.
5) From this point on I just add/subtract saved games coins as needed from consumable purchases and usage.
How does the extension handle things when google play services are not installed on the device? I think I recall a discussion about the extension displaying an app store link to install the game services?
Thanks for any comments. I'm a few weeks away from putting all of this into the app, but I'm hoping my thought process sounds doable. lol..