Possible to generate a migration for a model?

I already have a user model created, with all the properties I want.

Now I want to run

rails g scaffold users

but ofcourse it won't work b/c there is already a user model.

Is it 开发者_如何学Gopossible for me to generate a migration for the current user model (generate meaning create a migration script with the current model so I can re-run it later).

This way I can then destory the model, run the scaffold, then run the migration with the old columns that I setup earlier.

possible?

You can create a migration manually by hand using rails generate migration. Here's the output of that function's help:

Usage:
  rails generate migration NAME [field:type field:type] [options]

Options:
  -o, --orm=NAME  # Orm to be invoked
                  # Default: active_record

Runtime options:
  -f, [--force]    # Overwrite files that already exist
  -p, [--pretend]  # Run but do not make any changes
  -q, [--quiet]    # Supress status output
  -s, [--skip]     # Skip files that already exist

Description:
    Create rails files for migration generator.

This might happen when you are working with a model that is not database-backed, then you decide you want it to be, and extend ActiveRecord::Base and realized there is no table. I'd pop in to Rails console, and look at the methods on the class. You can print the setter methods out like this:

>> y Model.instance_methods(false).grep /\=/ # "Model" is the name of your class

Then I'd create a new migration like normal and define the columns with their types. e.g. if your Model has a name column of type string, rails g migration Model name:string. You might want to delete some of the generated files. If it doesn't work because it does a name match, I'd check if there is a force option, or I'd temporarily rename my existing model class, then name it back after the migration is generated.