Rails：根据不同的字段类型计算多个结果的总和

Question

我的用户have_many与他们相关的投资（模型）。我需要做的是每月计算他们所有的：（投资模型中的一列）的总和（我将在下面讨论）。

在我控制器，我有：

#get Investment types that are Roth IRAs, Traditional IRAs, etc. 
    @getira = Investment.where(user_id: current_user, investmenttype: ["Roth IRA","Traditional IRA","Other"]) 

通常我只想补充的.sum（：捐款）到该查询。但是，并非所有的贡献都是平等的。

的投资也有：contributionfrequency场，这是在用户选择“月刊”的字符串，“季度”或“每年”

所以我在同一控制器添加下面这一点：

investment = @getira.find(params[:contributionfrequency]) 

    # evaluate IRA contribution frequency 
    if investment.contributionfrequency == "Quarterly" 
     @contribution_quarterly = (investment.contribution.to_i * 4)/12 
    elsif investment.contributionfrequency == "Monthly" 
     @contribution_monthly = investment.contribution.to_i 
    elsif investment.contributionfrequency == "Annually"   
     @contribution_annually = investment.contribution.to_i * 12 
    end 

当我这样做，我得到这个错误：

没有ID找不到投资

我不确定是否进行了正确的查询，或者如果我没有在这里传递正确的字段。

Answer 1

您必须在下一行

investment = @getira.find(params[:contributionfrequency]) 

收到错误Couldn't find Investment without an ID这只是意味着params[:contributionfrequency]是nil即，你有没有在params传递的键:contributionfrequency。

按照与OP聊天会话，params[:contributionfrequency]取出并使用直接查询：

@contribution_quarterly = Investment.where(user_id: current_user, investmenttype: ["Roth IRA","Traditional IRA","Other"], contributionfrequency: ["Quarterly"]).sum(:contribution) 
@contribution_monthly = Investment.where(user_id: current_user, investmenttype: ["Roth IRA","Traditional IRA","Other"], contributionfrequency: ["Monthly"]).sum(:contribution) 
@contribution_annually = Investment.where(user_id: current_user, investmenttype: ["Roth IRA","Traditional IRA","Other"], contributionfrequency: ["Annually"]).sum(:contribution)