获取带有关联的Model.all并返回为json

Question

我正在尝试从模型中获取所有记录以及相关记录，然后使用.to_json生成json。我正在使用Rails 2.3 。

以下是该模型的一部分：

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

这就是我认为可行的代码：

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

但结果与我简单地Currency.all.to_json显然是相同的。如果使用ActiveRecord无法实现我的目标，请指导我应该使用哪种SQL。

Answer 1

这样做：

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

Documentation here.