Question

我是一支有4名球员的球队。每个玩家的位置都很重要，所以我认为我使用地图为我的玩家提供了一个很好的方式，其中包括：pos1，pos2，pos3 ，pos4

class Team {

Map players = [pos1:null, pos2:null, pos3:null, pos4:null]
static hasMany = [players:Player]

League league

static belongsTo = [club:Club]

static constraints = {
    league nullable:true
    players nullable:true

}
}

和我的玩家：

class Player{

static belongsTo = [club:Club, team:Team]

String firstname
String lastname

Team team



static constraints = {
    team nullable:true
    firstname nullable:true
    lastname nullable:true

}

public String fullname() {
    return firstname + " " + lastname + " - " + team?.id ?: "R"
}
}

我使用addToPlayers()方法让播放器自动更新，但是当我尝试以下操作时出现错误：

def player = new Player(firstname:"Peter", lastname:"Pan")
def team = new Team()
team.addToPlayers([pos1:player])

Stacktrace说：

Groovy.lang.MissingMethodException: No signature of method:
org.hibernate.collection.PersistentMap.add() is applicable for argument types:
(at.panda.Player) values: [at.panda.Player : null]
Possible solutions: any(), any(groovy.lang.Closure), any(groovy.lang.Closure), wait(),
wait(long), get(java.lang.Object)

at at.panda.PlayerController$_closure4.doCall(PlayerController.groovy:39)

at at.panda.PlayerController$_closure4.doCall(PlayerController.groovy)

at java.lang.Thread.run(Thread.java:662)

这花了我很多时间，我希望有人可以帮助我。我不需要坚持＆＃34; Map＆＃34;如果你有更好的解决方案。

Answer 1

如果域对象中有Map属性，则键和值必须都是字符串：Grails Manual: Object Relational Mapping。

但是你为什么要为你的球员使用地图？如果您只有四名球员，只需将您的球队定义为：

class Team {
    Player pos1
    Player pos2
    Player pos3
    Player pos4
    ...
}

Answer 2

就个人而言，我会像这样建立您的域名：

class Team {

  //Map players = [pos1:null, pos2:null, pos3:null, pos4:null]
  static hasMany = [players:Player]

  // The reference to league is now specified below in belongsTo       
  //League league

  static belongsTo = [club:Club,league:League]

  static constraints = {
    league nullable:true

    // must have 4 players
    players(size: 4..4)
  }
}

class Player{

  // Remove the reference to club as this can be retrieved through the Team
  static belongsTo = [/*club:Club,*/ team:Team]

  String firstname
  String lastname
  Integer position

  // Remove this duplicate reference to team
  //Team team        

  static constraints = {
    team nullable:true
    firstname nullable:true
    lastname nullable:true 

    // This should ensure that you can't create 2 players with the same position
    // in the same team
    position(unique:'team')   
  }
}

此模型可让您更轻松地按位置排列所有玩家，如果您决定要更改玩家数量，您需要做的就是更改约束players(size: 4..4)

我会考虑向Team添加addPlayer(Player player)方法，负责正确设置位置属性。

如果尚未测试上述任何代码，请小心处理。

域使用addTo Map导致错误

2 个答案: