Rails ERD – Entity-Relationship Diagrams for Rails

Rails ERD loads your Active Record models and processes all their attributes and associations (has_one, has_many, etc.). This information is combined into a single diagram. Because Rails ERD uses reflection instead of static analysis, it even recognises meta-programmed associations.The standard output may provide everything you are looking for. And if the customisation options are not sufficient, you can still use Rails ERD. It has a flexible API that allows you to inspect your models.