在Grails域对象中维护双方的自引用多对多关系

Question

我在使用grails时遇到了一些多对多关系的问题。有什么明显的错误有以下：

class Person { 
    static hasMany = [friends: Person] 
    static mappedBy = [friends: 'friends'] 

    String name 
    List friends = [] 

    String toString() { 
     return this.name 
    } 
} 

class BootStrap { 
    def init = { servletContext -> 
     Person bob = new Person(name: 'bob').save() 
     Person jaq = new Person(name: 'jaq').save() 
     jaq.friends << bob 

     println "Bob's friends: ${bob.friends}" 
     println "Jaq's friends: ${jaq.friends}" 
    } 
} 

我预计鲍勃做朋友JAQ，反之亦然，但我得到以下输出在启动时：

Running Grails application.. 
Bob's friends: [] 
Jaq's friends: [Bob] 

（I”中号使用Grails 1.2.0）

Answer 1

这似乎工作：

class Person { 
    static hasMany = [ friends: Person ] 
    static mappedBy = [ friends: 'friends' ] 
    String name 

    String toString() { 
     name 
    } 
} 

，然后在引导：

class BootStrap { 
    def init = { servletContext -> 
     Person bob = new Person(name: 'bob').save() 
     Person jaq = new Person(name: 'jaq').save() 

     jaq.addToFriends(bob) 

     println "Bob's friends: ${bob.friends}" 
     println "Jaq's friends: ${jaq.friends}" 
    } 
} 

我得到如下：

Running Grails application.. 
Bob's friends: [jaq] 
Jaq's friends: [bob]