CODEWITHSUNDEEP
grailsgrails-ormgrails-3.0
Dims
Dims

Reputation: 51259

Is there any difference between "belongsTo" constraint and just being a field in Grails?

I have created Child domain and made 2 parents to it. One parent I declared as a field. And another parent I declared with the help of belongsTo constraint.

package multipleparentsgrails

class Child {

    Parent2 parent2

    static belongsTo = [parent1: Parent1]

    static constraints = {
    }
}

Is there any difference between these ways?

How to eliminate differences? Can I have both belongTo and a member? Can I add cascading having a member?

Upvotes: 0

Views: 96

Answers (2)

wwwclaes
wwwclaes

Reputation: 1152

Yes, belongsTo defines cascading. If parent1 is deleted, so is child since it belongsTo parent1. If parent2 is deleted, Grails won't delete child automatically for you.

So, in this case, stating that a child belongsTo a parent wouldn't be very children-friendly :-)

You can define belongsTo in a few different ways, which allows you to define it on separate fields or to declare new fields. See the Grails documentation for further details, they have good examples of its use.

Upvotes: 1

Vinay Prajapati
Vinay Prajapati

Reputation: 7556

belongsTo plays significant role in parent child relationship. Here the class specified in belongsTo is the Parent / Owner of the relationship.

Following could be some comparison in normal has a and belongs To:

  1. belongsTo marks the referenced class as Owner of the relationship while same is not true in case of has a

  2. You don't need to worry about hibernate related cascading as relationship automatically will handle that i.e. you may specify cascade type but need not to give implementations otherwise in case of has a you have to use GORM DSL like stuff.

  3. Last but not least belongsTo also makes it mandatory to specify relationship owner while in case of has a constraints are the barriers.

Last but not least it might also make difference in gsp scaffolding as well but not sure about it.

Hope it Helps!

Upvotes: 2

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