I am currently developing a ruby application that has a large number of different objects. As part of this application, I would like to add a reporting engine that allows a user to create custom reports on virtually any variable within the application – for example, they could create a report that shows what percentage of customers have a telephone number, or the absolute number of suppliers whose street name starts with an E. The point is, they should be able to create any report on the data in the app, regardless of how obscure, without needing to rely on it having been created in the application already.
My question is: how do I start creating a structure that allows this to happen? Will it be necessary to specify all possible variables that could be used as part of a report (e.g. I would need to specify that customers.count, customers.email_address and suppliers.addresses.street_name are all variables available to the reporting engine for the example above), or could these somehow be made available automatically?
If it is necessary to specify the variables, what would be the best way to do this?
I have searched for some resources on this, but have not yet found any – if anyone can recommend a source, it would also be appreciated.
Thanks!
Consider yourself warned that this likely violates YAGNI. I would highly recommend building reports first for the most common types of reports your users will want, so that you can make them usable and pretty. Doing this at the abstract level is an order of magnitude more complex, is error prone, may lead to some security issues if you’re not careful, and will be difficult to make pretty reports rather than generic looking ones.
That said, take a look at something like Active Admin, which provides custom filters and data exports. You should be able to add custom scopes to have it do what you want, but if it still doesn’t, then looking at the implementation should give you a good idea of what’s involved.