Grails - How do I create a model-restricted drop-down list for a view owned?

Question

I am learning grails and I have a problem.

I have 2 classes, say:

    class Book {

      String name
      String description
      static belongsTo = Category
      Category category

      static constraints = {
           name(nullable:false, blank:false)
               description(nullable:true, maxSize:5000)
      }

   class Category {

      String name
      static hasMany = [books:Book]
      Set books
      static constraints = {
              name(nullable:false, blank:false)
      }

      String toString(){
              this.name
      }
   }

When I create a book, I want to see a drop-down list with all category names. If I do not choose a category, I cannot create this book. If there are no categories in the database, than I could not create the book until I create and select a category.

Is it possible for these functions to be generated (using grails generate-all) from domain classes if I have the correct constraints and fields? If so, how?

Answer 1

, , . , , :

static belongsTo = [category:Category]

, null: false

static constraints = {
           name(nullable:false, blank:false)
           description(nullable:true, maxSize:5000)
           category(nullable:false)
      }

.