A few intermediate Rails3 Questions

I'm building an app called "CourseWork to dig into rails/develop my skills and I have a question about how to structure it. Users have a resource called "CourseGrading" that is able to create categories and belongs to "Course". Each "category" should have a name, a percentage out of 100 and a course_id. I need to add these percentages to开发者_开发技巧gether and alert users if the total isn't 100 while still saving.

Then the user's generated "categories" should populate an enum_string specific to that user in a resource called "CourseAssignment" which has a name, description, category and finalgrade.

Can anyone give hints or resources for how best to accomplish this? Thanks

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You probably want to take a look at Active Record Callbacks. These will allow you to insert some code to be run when creating/validating/updating/deleting models.

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You should probably make use of the ActiveRecord validations.

Check out this guide that explains how to write your own custom validator. Your custom validator would run when the form gets submitted, and in it, you would grab the percentage params and do your check. If it's not what you expect, you can just add an error to the form and the validation process will just kick the user back to the form page and display the error.