Module: Wrong::Capturing

Included in:
Chunk, Helpers
Defined in:
lib/wrong/capturing.rb

Instance Method Summary collapse

Instance Method Details

#capturing(*streams) ⇒ Object

Usage: capturing { puts “hi” } => “hin” capturing(:stderr) { $stderr.puts “hi” } => “hin” out, err = capturing(:stdout, :stderr) { … }

see www.justskins.com/forums/closing-stderr-105096.html for more explanation



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# File 'lib/wrong/capturing.rb', line 10

def capturing(*streams)
  streams = [:stdout] if streams.empty?
  original = {}
  captured = {}

  # reassign the $ variable (which is used by well-behaved code e.g. puts)
  streams.each do |stream|
    original[stream] = (stream == :stdout ? $stdout : $stderr)
    captured[stream] = StringIO.new
    reassign_stream(stream, captured)
  end

  yield

  # return either one string, or an array of two strings
  if streams.size == 1
    captured[streams.first].string
  else
    [captured[streams[0]].string, captured[streams[1]].string]
  end

ensure

  streams.each do |stream|
    # bail if stream was reassigned inside the block
    if (stream == :stdout ? $stdout : $stderr) != captured[stream]
      raise "#{stream} was reassigned while being captured"
    end
    # support nested calls to capturing
    original[stream] << captured[stream].string if original[stream].is_a? StringIO
    reassign_stream(stream, original)
  end
end