I am building a custom app yet am not sure about step 7. What solution files should I add to Xcode? My database is hosted online and is just over 1 GB in size. Should I add the whole thing or just the iOS layouts?
You need to add the entire file.
That is, unless you write a specific interface for your iOS xcode compiled solution that will use the data from your hosted file. In which case you have a new file to build. If you want to go that route look into the "data separation model" for filemaker.
If you just want to have a usable compiled app for iOS, just add the whole file.
I assume you are using the iosAPPSDK. You would just need the database you created to login to the hosted database.
iosAPPSDK is FMGo, where FMGo lets you select the hosted databases the iosAPPSDK does not, you have to create a database that logins to the hosted database.
Here is webinar about iosAPPSDK Webinar Making FM Apps for Apple's App Store - FileMaker User Group Meeting Fri Jan 15th - YouTube
RC also has a paid training video FileMaker iOS App SDK.
Our database is hosted too. How do I make sure the data changes gets added to our hosted solution?
By either using the data separation model as I noted, or developing an "opener" file that opens your hosted solution from the one that's embedded in iOS.
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