如何在grails中为hasMany属性编写约束

Question

我在grails应用程序中有三个类

class Category {
    String name
}
class Application {
    String name
    static hasMany =[specialCategoryies:SpecialCategory]
}
class SpecialCategory {
    Category category
    Integer points
    static belongsTo =[application:Application]
}

在此处保存应用程序实例时，我不希望保存重复specialCategories值，如。。specialCategories不具有相同的类别值。。

application.addToSpecialCategoryies(newSpecialCategory(category:Category.get(1),points:2))
application.addToSpecialCategoryies(newSpecialCategory(category:Category.get(1),points:3))

这里我的应用实例应该会出现类别值重复的错误。。那么如何定义域类中hasMany属性的约束。。。。。。？建议如何编写约束以避免类别的重复值

Answer 1

您可以尝试在应用程序约束部分使用自定义验证器。例如，检查重复属性值的一种方法是将值收集到一个数组中，并将其与相应的唯一数组（删除重复元素）进行比较：

class Application {
    String name
    static hasMany =[specialCategoryies:SpecialCategory]
    static constraints = {
        specialCategoryies validator: { specialCategories, obj ->
            def specialCategoriesIdArray =  specialCategories.collect {it?.category?.getId()}
            return (specialCategoriesIdArray.size() == specialCategoriesIdArray.unique().size())?true:'application.validator.specialcategoryduplicate.error'
        }
    }
}

当试图用现有类别保存特殊类别时，保存时会抛出验证错误。您可以使用以下工具进行测试：

    def cat1 = new Category(name:"Cat 1").save(flush:true)
    def cat2 = new Category(name:"Cat 2").save(flush:true)
    def app = new Application()
    app.name = "Test"
    app.addToSpecialCategoryies(new SpecialCategory(category: Category.get(1), points:2))
    app.addToSpecialCategoryies(new SpecialCategory(category: Category.get(2), points:2))
    app.addToSpecialCategoryies(new SpecialCategory(category: Category.get(1), points:3))
   if ( app.save(flush:true)   ){
          log.info "Saved!"
   }   else {
          log.error "NOT Saved. Error:"
       app.errors.each {
           log.error it
       }
   }