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copied!<h1>1) Domain model</h1> <p>Keep your code simple. Don't create generic data model. It's way to hell. When you personToPerson and personToStore keep separate, it's much easier to follow your code. </p> <p>Actually suggested solution makes it possible to access relations as consolidated and independent list simultaneously.</p> <p>For this problem I would use <a href="http://grails.org/doc/latest/guide/5.%20Object%20Relational%20Mapping%20(GORM).html#5.2.3%20Inheritance%20in%20GORM" rel="nofollow noreferrer">inheritance feature in GORM</a>.</p> <p>Your classes would look like this:</p> <pre><code>class Person { String name static hasMany = [personToPerson:PersonToPerson, personToProduct:PersonToProduct, personToStore:PersonToStore] static mappedBy = [personToPerson:"from"] } class Product{ String productName } class Relationship{ String note } class Store{ String storeName } class PersonToPerson extends Relationship{ Person from Person to String relation static constraints = { relation(inList:["Friend to", "Enemy of", "Likes", "Hates"]) } static belongsTo = [ from:Person ] } class PersonToProduct extends Relationship{ Person person Product product String relation static constraints = { relation(inList:["likes", "dislikes"]) } static belongsTo = [ person:Person ] } class PersonToStore extends Relationship{ Person person Store store String relation static constraints = { relation(inList:["Stock person", "Owner", "Manager", "Patron"]) } static belongsTo = [ person:Person ] } </code></pre> <p>DB schema for Person, Product and Store is usual. But for Relational domains look like this:</p> <p><strong>Relationship</strong></p> <pre><code>Field Type Null Default id bigint(20) No version bigint(20) No note varchar(255) No class varchar(255) No person_id bigint(20) Yes NULL product_id bigint(20) Yes NULL relation varchar(8) Yes NULL from_id bigint(20) Yes NULL to_id bigint(20) Yes NULL store_id bigint(20) Yes NULL </code></pre> <p>Relationship domain makes possible to access all relational domain throw one domain.</p> <h1>2) Constraint</h1> <p>Just switch <em>inList</em> to <em>validator</em>. Than you can store constrain in file or DB. See <a href="http://www.grails.org/Validation" rel="nofollow noreferrer">documentation</a> or <a href="http://grails.1312388.n4.nabble.com/Dynamic-inList-constraints-td2279264.html" rel="nofollow noreferrer">file example</a>.</p> <p>Example how to store constraint values in DB. First create a domain object.</p> <pre><code>class Constrain{ String name String type } </code></pre> <p>Than the domain class looks:</p> <pre><code>class PersonToPerson extends Relationship{ Person from Person to String relation static constraints = { relation(nullable:false, validator:{val, obj -> def list = Constrain.findAllByType('person').collect{it.name} return list.contains(val) }) } static belongsTo = [ from:Person ] } </code></pre>

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