Question

BACKGROUND

I have a multidimensional hash which I want to perform a check to ensure that the lookup found a match, but it does not seem to work the same as single dimension hash. My code works for a case where it finds a match, but not for a non-match. I have read posts in which under certain circumstances the hash will automatically generate a key for a non match, which I think will result in a NIL since I did not specifically set a value. The error message I get for a non-match case is:

can't convert Hash into String (TypeError)

Link to my project for context: https://github.com/elvisimprsntr/siriproxy-redeye

Excerpt of code and hyperlinks to source:

redeyeconfig.rb

# Channel number and command syntax to actual RedEye device commandIds
# Note: Must all be lower case. Use multiple entries for variability in Siri response.
@cmdId = Hash.new(&(p=lambda{|h,k| h[k] = Hash.new(&p)}))
@cmdId["all"]["cable box"]["0"]         = "/commands/send?commandId=3"
@cmdId["all"]["cable box"]["zero"]      = "/commands/send?commandId=3"
@cmdId["all"]["cable box"]["1"]         = "/commands/send?commandId=4"

siriproxy-redeye.rb

  def send_command(command)
    commandid = @cmdId[@reRoom][@reDevice][command.downcase.strip]
    unless commandid.nil?
        say "OK. Sending command #{command}."
# FIXIT: Does not properly handle no match.  Results in "can't convert Hash into String (TypeError)"
#   This may be due to the fact that dynamically created multidimensional hash will create new keys if a match is not found which will pass the NIL check.
        Rest.get(@reIp[@reSel] + @roomId[@reRoom] + @deviceId[@reRoom][@reDevice] + commandid)
    else
        say "Sorry, I am not programmed for command #{command}."
    end
    request_completed   
  end

QUESTION

How do I define/initialize my hash differently and/or test for a non-match?

Answer 1

You don’t get nil or a String back in case of a failed lookup – instead you get an empty Hash.

Check if commandid.is_a?(Hash) and commandid.empty? to know if the lookup failed or not.