Ruby-on-rails 在finder方法上出现“错误数量的参数”错误
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Getting "wrong number of arguments" error on finder method
提问by Dave
I'm using Rails 4.2.3 (and using MySQL 5.5.37). I'm having difficulty writing a finder method for one of my models. I have columns “user,” “object,” and “day”, but the following
我正在使用 Rails 4.2.3（并使用 MySQL 5.5.37）。我在为我的一个模型编写 finder 方法时遇到了困难。我有“用户”、“对象”和“日”列，但以下内容
def find_by_user_object_and_day
respond_to do |format|
@current_user = User.find(session["user_id"])
format.js {
render :text => Userobject.find_by_user_and_object_and_day(:user => @current_user, :object => params[:object], :day => params[:day])
}
end
end
produces the error
产生错误
F, [2016-02-05T16:49:42.934112 #12058] FATAL -- :
ArgumentError (wrong number of arguments (given 1, expected 3)):
app/controllers/user_objects_controller.rb:77:in `block (2 levels) in find_by_user_object_and_day'
app/controllers/user_objects_controller.rb:74:in `find_by_user_object_and_day'
How do I properly specify the arguments to the finder method? I haven't explicitly defined that finder method because I thought the “and” syntax would work.
如何正确指定 finder 方法的参数？我没有明确定义那个 finder 方法，因为我认为“and”语法会起作用。
采纳答案by miler350
The error says:
错误说：
ArgumentError (wrong number of arguments (given 1, expected 3))
This means you're supposed to pass in 3 distinct arguments, but you passed in 1. It looks like you passed in a hash of values instead of standalone values.
这意味着您应该传入 3 个不同的参数，但您传入了 1 个。看起来您传入的是散列值而不是独立值。
Replace:
代替：
Userobject.find_by_user_and_object_and_day(:user => @current_user, :object => params[:object], :day => params[:day])
With this:
有了这个：
Userobject.find_by_user_and_object_and_day(@current_user, params[:object], params[:day])
回答by Richard Peck
find_by_some_column_and_another(dynamic finders) have been deprecated in favour of find_byin Rails 4+:
find_by_some_column_and_another(动态查找器)find_by在 Rails 4+ 中已被弃用：
@user = UserObject.find_by user: @current_user, object: params[:object], day: params[:day]
Using the above code structure shouldsolve your issue (find_bytakes a hash and requiresonly 1argument).
使用上面的代码结构应该可以解决你的问题（find_by需要一个散列并且只需要1参数）。
If you still want to use your dynamic find method, you need to ensure you have both the params[:object]and params[:day]values populated, as well as dropping the user:/object:/day:declarations (as mentioned by @miler350)
如果你仍然想使用动态查找方法，你需要确保你有两个params[:object]和params[:day]值填充，以及丢弃user:/ object:/day:声明（如提及@miler350）
Secondarily, you also need to make sure that you're constructing your actions properly:
其次，您还需要确保正确构建您的操作：
def find_by_user_object_and_day
@current_user = User.find session["user_id"]
@user_object = UserObject.find_by user: @current_user, object: params[:object], day: params[:day]
respond_to do |format|
format.js { render text: @user_object }
end
end
