Ruby YAML problem when deserializing a nested object structure

I have 3 classes that have the following relationship:

Battlefield have an array of teams.

BattleTeam have an array of members, and a reference to the Battlefield.

Jaguar is a member of a BattleTeam and has a reference to it.

If I serialize/deserialize Jaguar and up to BattleTeam, there is no problem. The problem happens when serializing/deserializing a Battlefield.

Serializing it yields the appropiate result, but deserializing it turns the members in BattleTeam to nil.

Let me show you:

>> j = Jaguar.new
=> #<Jaguar:0xa2221f8 @vitality=nil, @spirituality=nil, @log=nil, @name=nil>

#A battleteam might have many members:
>> t = BattleTeam.new
=> #<BattleTeam:0xa21fafc @members=[], @dead_members=[]>

#A battlefield might have many teams:
>> b = Battlefield.new
=> #<Battlefield:0xa2075d8 @teams=[]>

#Add a member to the team
>> t.add_member(j)
=> #<BattleTeam:0xa21fafc @members=[#<Jaguar:0xa2221f8 @vitality=nil, @spirituality=nil, @log=nil, @name=nil, @battle_team=#<BattleTeam:0xa21fafc ...>], dead_members[]

#Add a team to the battlefield
>> b.add_team(t)
=> #<Battlefield:0xa2075d8 @teams=[#<BattleTeam:0xa21fafc @members=[#<Jaguar:0xa2221f8 @vitality=nil, @spirituality=nil, @log=nil, @name=nil, @battle_team=#<BattleTeam:0xa21fafc ...>>], @dead_members=[], @battlefield=#<Battlefield:0xa2075d8 ...>>]>

#Serialize and deserialize the jaguar object (it works as expected):
>> YAML::load j.to_yaml
=> #<Jaguar:0xa1e3cdc @vitality=nil, @spirituality=nil, @log=nil, @name=nil, @battle_team=#<BattleTeam:0xa1e4204 @members=[#<Jaguar:0xa1e3cdc ...>], dead_members[], battlefield#<Battlefield:0xa1e4038 @teams=[#<BattleTeam:0xa1e4204 ...>]

#Serialize and deserialize the battle team object (it words as expected):
>> YAML::load t.to_yaml
=> #<BattleTeam:0xa1d0664 @members=[#<Jaguar:0xa1cfee4 @vitality=nil, @spirituality=nil, @log=nil, @name=nil, @battle_team=#<BattleTeam:0xa1d0664 ...>], dead_members[], battlefield#<Battlefield:0xa1d0470 @teams=[#<BattleTeam:0xa1d0664 ...>]

#Serialize and deserialize the battle team object
#(here the @members array is deserialized as nil, this is not expected!):
>> YAML::load b.to_yaml
=> #<Battlefield:0xa1c370c @teams=[#<BattleTeam:0xa1c33b0 @members=nil, @dead_members=[], @battlefield=#<Battlefield:0xa1c370c ...>]

>> YAML::load(b.to_yaml).teams[0].members
=> nil


#Here is the generated yaml, it looks right, the member is there:
>> puts b.to_y开发者_JAVA技巧aml
--- &id002 !ruby/object:Battlefield 
teams: 
- &id001 !ruby/object:BattleTeam 
  battlefield: *id002
  dead_members: []

  members: 
  - !ruby/object:Jaguar 
    battle_team: *id001
    log: 
    name: 
    spirituality: 
    vitality: 
=> nil

Anyone knows what's wrong with this?

I really don't know much about YAML or serializing / deserializing.. But look :

puts b.to_yaml --- &id002 !ruby/object:Battlefield teams: - &id001 !ruby/object:BattleTeam battlefield: *id002 dead_members: []

members: - !ruby/object:Jaguar battle_team: *id001 log: name: spirituality: vitality: => nil

How come battlefield and battleteam look like this:

--- &id002 !ruby/object:Battlefield 
- &id001 !ruby/object:BattleTeam 

And Jaguar looks like this:

  - !ruby/object:Jaguar 

The id seems to be missing... ?