Ruby字符串“ nil”转换为nil：NilClass nil（与nil.inspect相反）

Question

I wonder howto get from a string "nil" the nil:NilClass?

nil.inspect -> "nil"

I wish something like:

"nil".to_nil -> nil

Update:

As I write in the comment bellow it's easier to :

params[:form].each_pair{|k,v| fields[k] = k.to_s.include?('_id') ? v.to_nil : v

then

params[:form].each_pair{|k,v| fields[k] = k.to_s.include?('_id') ? (v == "nil" ? nil : v) : v }

Answer 1

I don't see the point of a to_nil , because well, it's always nil , so write nil . But if your question is which is the inverse operation of inspect , you can use eval :

eval("nil") #=> nil

Answer 2

Re-open the string class if you want this functionality globally.

class String
  def to_nil
    if self == 'nil'
      nil
    else
      self
    end
  end
end

'nil'.to_nil # => nil
'another string'.to_nil # => "another string"

Answer 3

You could eval the string "nil" for example:

=> eval("nil").nil?
irb> true