using inheritance in grails domain classes

Question

I am having monthly domain classes to partition transactions into by month basis [TxnSummaryJan, TxnSummaryFeb..etc]. Now I am trying to create a Month domain class which is abstract and has all the fields defined in it so that the Jan,Feb classes just extend this class and thats it. Now I have set the

tablePerHierarchy = 0

in the mapping for the month class so that grails does not create a table for this class.

Now the tables are getting created properly but when I execute

Month.createCriteria().get( eq('userid',1)).list()

it gives me error that get() function is not available to Month class. But it runs when I give for example

TxnSummaryJan.createCriteria().get(eq('userid',1)).list()

What am I missing here since according to the domain model I should get the results when I query the base class?

Also where to place the Month Domain class? Do I need to place the Month Domain outside of src/Domain so that its table is not created?

Regards Priyank

codewandler codewandler · Accepted Answer · 2014-01-31T22:17:30

When using tablePerHierarchy = false this also implies that the base table will not be created. Instead it will create one table per month. The only way of doing queries against Month would be doing queries on all specific sub-classes of Month and then somehow merging the results. I think this could be possible with GORM, but also would imply strange/complicated queries with maybe unexpectable performace issues.

If your design intention is to not create the base table in the database, then just move your base-class to src/groovy and mark it as abstract. Then set tablesPerHierarchy to true as it is default. This way all your data ends up in one table, but you can access all your data at once.

see http://grails.org/doc/latest/guide/GORM.html#inheritanceStrategies for reference.

using inheritance in grails domain classes

1 Answers