title: How do hasMany and hasOne work in Grails?
body: <p>I am having problems defining one-to-one and one-to-many relationships with domain classes.
  I have the following domain classes </p>
  
  <pre><code>class Team {
      static hasMany = [players: Player]
      static hasOne = [coach: Coach]
  }
  
  class Person {
      String name
  }
  
  class Player extends Person {
  }
  
  class Coach extends Person {
  }
  </code></pre>
  
  <p>So my questions are:</p>
  
  <p>1- Do I need to declare a variable <code>team</code> in Player and in Coach ? </p>
  
  <p>2- Do I need to declare a <code>belongsTo</code> as well?</p>
  
  <p>3- Considering the above classes, is it preferable to use hasOne?</p>
  
  <p>Thank you.</p>