如果我没有链接域类中的字段，如何将表格与grails中的条件联系起来

Question

I have two classes in domain model:

class Project {
   String name
   Integer fund
}

class Task {
   String name
   Integer weight
   Project project
}

How can I get Project with Task.name = "something"?

If i need Task with Project.name = "something", I can do it with criteria by createAlias, but how can I join Task in

c = Project.createCriteria()
   criteriaRes = c.list {
}

Answer 1

I'm not sure if this will be helpful, but I've worked a lot with SQL so when I'm stuck figuring out how to create a criteria or where query I do it first in HQL since it's similar to SQL. If you don't plan on using a NoSQL database HQL is a good choice, but criteria and where queries are portable across GORM implementations.

So an HQL query that does what you want is

def projects = Task.executeQuery(
   'select t.project from Task t where t.name=:taskName',
   [taskName: 'something'])

An analagous criteria query would then be

def projects = Task.createCriteria().list {
   eq 'name', 'something'
   projections {
      property 'project'
   }
}

Answer 2

In addition to Burt's answer, I think you need (or should have as a best practice) the relationship between the 2 domain classes properly defined:

class Project {
   String name
   Integer fund
   static hasMany = [tasks: Task]
}

class Task {
   String name
   Integer weight
   static belongsTo = [project: Project]
}