Ruby on Rails：脚手架、Model 和属性

Question

I have an odd question. Let's assume I create something using scaffolding. This should build me lots of different files including files in the model, view, and controller. I passed it not only the name of the scaffold, but also attributes/fields/variables. When I looked at the model of the scaffold I generated, I don't see those attributes listed. I am puzzled. How does Rails know that a field exists or not? Can I change them in the future to not have a certain attribute or add a new attribute?

I apologize about this question. I am feeling rather overwhelmed by trying to learn this framework. I'm originally a java developer working on small school projects and I want to branch out. I purchased and have been trying to read the Agile Web Development with Rails book that I keep hearing about. It's good, but I'm still feeling rather lost in how everything works. Am I just trying too hard to understand how rails works?

Thank you all!

Answer 1

Scaffolding is a way to generate code, which you will write otherwise. Generated code is only a starting point and not the final version of things.

Model: When you scaffold, you pass in fields which you need right now. Rails will generate the model and the migration for you. When you run the migration, it will create the table in db with the columns/fields you passed. Model can dynamically determine what are the fields in the table.

If you need to add/remove fields in future, you would need to write another migration to add remove them, which you can do using a rails generate migration

Controller: Scaffolding generates a standard controller with 7 actions which respond to the restful resource(your model): new, create, edit, update, destroy, show, index. You can add or remove actions as you please. You would need to alter the routes accordingly if you add/remove the actions.

Views: Rails scaffolding will generate the barebone standard views, with forms for your fields and views to show those fields. You can customize the looks and change the views as per your requirements.

I hope it clarifies things.

Scaffolding is not the only way to generate code. There are generators specific to model, migrations and controllers.

I hope you have read RailsGuides . They are very helpful for beginners as well as people familiar with rails.