Question

I’m working on a unit converter app and I want to be able to convert several categories of objects (length, height, mass, temperature, etc). I also want to use core data to store the conversion factors so I’m not writing hundreds of if statements. How should I structure my data model? Should I have an entity for each category of conversions?

Thanks

Answer 1

Make a class Category, which will have a string name (length, mass, charge, etc.) and a many-to-one relationship with Unit, which will have a name, abbreviation, and factor. The factors within each category will obviously need to be scaled to a common unit. You can then ship with a database, and offer users the chance to add their own units if they need one you haven’t provided.