I added support for binding a property object to
Preferences a while back and just didn’t have the time to blog about it. I didn’t consider it too crucial as the functionality is very simple to figure out, the only difficult part is knowledge of the features existence.
Some objects make sense as global objects, we can just use the
Preferences API to store that data directly but then we don’t have the type safety that property objects bring to the table. That’s where the binding of property objects to preferences makes sense. E.g. say we have a global
Settings property object we can just bind it to preferences using:
So if settings has a property called
companyName it would bind into
Preferences under the
We can do some more elaborate bindings such as:
PreferencesObject.create(settingsInstance). setPrefix("MySettings-"). setName(settingsInstance.companyName, "company"). bind();
This would customize all entry keys to start with
MySettings- instead of
Settings.. This would also set the company name entry to
company so in this case instead of
Settings.companyName we’d have
A part of getting this to work seamlessly is the
getAndSet API added to the
Preferences API. This is a bit of a weird API but it’s pretty useful so lets explain it by example.
Say we have a user setting for refresh as an integer in minutes:
int refresh = Preferences.get("refresh", 60);
That will return the refresh value as 60 if it doesn’t exist. The problem is: “how do we know we got back the default?”.
Normally that isn’t a big deal but if we have one path that invokes
Preferences.get("refresh", 60) and another one that does a
Preferences.get("refresh", 100); how can we tell which one is correct?
I could use
Preferences.get("refresh", 60); and if 60 is returned I can invoke
set to explicitly set the 60 value just to make sure that 60 will be used from now on. But that would mean changing preferences with every invocation even if the data didn’t change.
getAndSet() essentially solves that problem. You get the data one and if the default is used that default is then stored into the
Preferences so you can’t get inconsistent results for a specific entry.