使用Active Model Serializer或JSON渲染sum属性

Question

我的默认代码是Lab.all，当我只是像Lab.all.to_json那样呈现完美的json

{"id":1,"lab_id":1,"test_id":2,"price_cents":20000,"duration":null,"created_at":"2016-02-26T14:40:40.825Z","updated_at":"2016-02-26T14:40:40.825Z"}

我有以下范围：

@lab_tests = LabTest.group(:lab).sum(:price_cents)并以json：

返回以下内容

{"#\u003cLab:0x007f8e0a44afa8\u003e":20000}

如何让它像这样渲染json：

  {"id":1,"lab_id":1,"test_id":2,"price_cents":20000,"duration":null,"created_at":"2016-02-26T14:40:40.825Z","updated_at":"2016-02-26T14:40:40.825Z", "price_cents":200000 }

我尝试在我的范围中添加.select参数，但即使这样也不会改变任何内容。