Hi Kasper, thank you for your quick response. I was having a look at some stackoverflow threads [1][2] and was start thinking of moving to an interface solution. With your response I've got a much clear idea.
[1]http://stackoverflow.com/questions/6511453/extending-a-enum-in-java [2] http://stackoverflow.com/questions/2642281/is-it-possible-to-extend-java-enums Kind regards, Alberto 2015-07-23 12:36 GMT+02:00 Kasper Sørensen <i.am.kasper.soren...@gmail.com>: > Hi Alberto, > > I am thinking that this reminds me a bit of the time (some releases back) > when we converted ColumnType from an enum into an interface. That change > opened up a lot of doors IMO. And a similar change to the FunctionType > could do the trick. > > What I have in mind is: > > * Add an interface called AggregateFunction. This interface will have the > "aggregation specific" methods related to AggregateBuilder etc. > * Add an interface called ScalarFunction. This interface will have some > method that could be used to do the scalar transformation in memory (for > those DataContext implementations that don't support the function > natively). > * Rename the current FunctionType enum into DefaultAggregateFunction and > let it implement AggregateFunction > * Add a new FunctionType _interface_ which has static final references to > the aggregate functions. Thereby we facilitate that existing code will > work, although it will need to be recompiled. > > Once these changes have been done then we can start looking at parsers, how > to execute the different types of functions in different kinds of > DataContext implementations etc. But having the split in the interfaces > will allow us to much better generalize that I think. > > Best regards, > Kasper > > 2015-07-23 12:28 GMT+02:00 Alberto Rodriguez <ardl...@gmail.com>: > > > Hi all, > > > > I've just started having a look at how to add scalar functions like > > SUBSTRING, CONCAT, UPPER... to MetaModel. > > > > I started by adding these functions to the MetaModel parser. There is > > already a FunctionType enum that takes care of all the aggregate > functions > > (SUM, COUNT, AVG...) This FunctionType is used in the SelectItemParser to > > find out the function type and parse it accordingly. > > > > Not sure if I should add a new "ScalarFunctionType" enum or modify > somehow > > the existing one to take into account the new scalar functions. I do not > > like the idea of having quite different "semantic" elements within the > same > > enum type but neither like the idea of having to ask everywhere whether > the > > function is scalar or not. > > > > I'm thinking of creating kinda enum hierarchical data structure, but > still > > not sure how to do it because the FunctionType has several methods that > are > > very coupled to the aggregate functions (abstract AggregateBuilder, > > evaluate...) > > > > Any ideas? > > > > Kind regards, > > > > Alberto > > >
