Best way to design Domain with constant in grails

Question

I have lots of domain classes in my project. Many of them has type column. For example: User table has userType column, Book table has bookType column. I often pass these types into GSP g:select source by calling BookType.list() method. But problem is if GSP contains lots of g:select then I have to execute lots of redundant query.

And another problem is when I create a new Domain instance, I have to get these constant types from DB by following way

Book book = new Book();
book.bookType = BookType.findByName(BookTypes.COMICS);

Here I also have the same problem, I have to execute redundant query. Is there any good design to do all these stuff without executing these redundant queries?

Answer 1

If the types are not very volitile, I assume that is the case because I can see you defined an enum for type. Try using enum, totally -- I mean, don't bother with the database table at all to back that up. For example,

enum SomeType {

    TYPE1(1, "Type 1"),
    TYPE2(2, "Type 2"),
    TYPE3(3, "Type 3")

    final int id
    final String value

    private SomeType(int id, String value) {
        this.id = id
        this.value = value
    }

    // Might be needed for <g:select> tags, I'm not very sure
    int getKey() { id }

    static SomeType byId(int id) {
        values().find { it.id == id }
    }
}

Then, in your domain, do something like,

class SomeDomain {

    static constraints = {
        ...
        type nullable: false
        ...
    }

    ...
    SomeType type
}

Then, you can simply do something like this,

SomeDomain book = new SomeDomain(..., type: SomeType.TYPE1, ...);