I'm a newbie in rails and its a great platform.
I created an application but removed all the migration scripts.
I want to create the database with the tables from my existed models.
I can't find it on the net and I'm sure that might be an option to do that like any other platform (java hibernate, etc)
the command rails generate... only create the table without columns but I have columns in the existed models. so how can I do that?
Thanks!
If you've accidentally scrubbed your models and don't have any migrations, you can still generate a db/schema.rb file by running rake db:migrate and using that instead. It should reflect the current state of your database no matter what you've done to it.
If you create a migration with the important parts of this in it, as you'll notice the format is very similar, you will be able to replicate that configuration on other systems.
This is a bit of a heavy-handed way to do it, though. Each model should have its associated migration. Generally these are never deleted and only modified if strictly necessary, preserving a history of how the schema evolved into its final state.
If I understand your question correctly, there really isn't a way to construct your database tables from your ActiveRecord model classes - it's best to think of ActiveRecord models as more of a mapping between different flavors of relational databases and Ruby objects. In other words, ActiveRecord models abstract away the details of a database in order to become database-independent. They make your database data more easily accessible in Ruby. In doing so, they don't have the power to construct your tables. Think of them as very pretty getters and setters rather than a binding to a database.
This is exactly why migrations exist - they contain the database-specific stuff. They essentially contain the "other half" of your model definition - most of the application level stuff (like relations, which don't exist in, say, MySQL, right? They are an ActiveRecord convention) is defined on your model, but, for example, if you want to have a string on your Foo model, you define that in your migration, and the appropriate getters and setters will be available on your model for you to play with this string.
tl;dr: you need your migrations. The fact that they exist in Rails is an intentional design decision to separate the Ruby half of the models from the database half.
