CODEWITHSUNDEEP
ruby
Chris
Chris

Reputation: 71

TypeError: no implicit conversion of nil into String

Trying to decode a bin file in ruby script but after running the script I get the following error test.rb:57:in read': no implicit conversion of nil into String (TypeError) from script:57:in'

Any idea what could be the problem?

Thanks in advance

require 'bindata'

class Decode < BinData::Record # size 4+
  uint32le :record_count
  array    :records, :type => :cube_main_bin_record, :initial_length  => :record_count
end


begin
  f = ARGV[0] unless ARGV[0].nil?
  bin = File.read(f)

  Decode.read(bin).records.each_with_index do |rec, num|
    puts "Record #{num} #{rec.to_binary_s.length}"
    p rec
  end
end

Upvotes: 0

Views: 10077

Answers (1)

Jim U
Jim U

Reputation: 3366

Because File.read requires a string parameter and f defaults to nil when you invoke the script without a command line argument

f = ARGV[0] unless ARGV[0].nil?     # f defaults to nil when ARGV[0] is nil
bin = File.read(f)                  # bin = File.read(nil)   BOOM

Here is a refactoring of your code:

...
f = ARGV[0]
abort "filename required" unless f
bin = File.read(f)
...

These changes accomplish two things:

  1. When the script is invoked without the required filename, it will gracefully abort with an explanation of the problem.
  2. Simplifies the code by removing unless ARGV[0].nil? which doesn't do anything useful will be misleading to anyone maintaining your code in the future, including yourself

Upvotes: 2

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