获取与关联的Model.all并返回为json

Question

我试图从我的模型中获取关联记录的所有记录，然后使用.to_json生成json。我正在使用Rails 2.3。

这里是一块模型的一部分：

class Currency 
    has_many :exchange_from, :class_name => "CurrencyExchange", :foreign_key => "currency_from_id", :dependent => :destroy 
    has_many :exchange_to, :class_name => "CurrencyExchange", :foreign_key => "currency_to_id", :dependent => :destroy 

这是代码，我认为将工作：

Currency.all(:include => [:exchange_from, :exchange_to]).to_json 

但结果是exacly 相同我会做简单的Currency.all.to_json。如果使用ActiveRecord无法实现我的目标，请指导我使用哪种SQL。

Answer 1

这样做：

Currency.all(:include => [:exchange_from, :exchange_to]).to_json(:include => [:exchange_from, :exchange_to]) 

Documentation here.