Putting the results of pp (or anything outputted to console) into a string

Question

We know

require \'pp\'
a=[\"value1\", \"value2\", \"value3\"]
pp a

pretty prints the array as an output to the console. How do I get that p

Answer 1

This is a nice 'n simple way to capture the output of pp:

require 'pp'

asdf = {'a' => 1, :b => 2, 'c' => %w[ho daddy]}
foo = PP.pp(asdf, '')
puts foo
=> {"a"=>1, :b=>2, "c"=>["ho", "daddy"]}

Capturing STDOUT, which is the default channel used by puts and print and that things like pp piggyback on, is a bit more complex:

require 'pp'
require 'stringio'

asdf = {'a' => 1, :b => 2, 'c' => %w[ho daddy]}
puts 'Writing to STDOUT...'
pp asdf

# remember the old STDOUT stream...
old_stdout = $stdout

# ...and create a new stream that writes to a string.
captured_stdio = StringIO.new('', 'w')
$stdout = captured_stdio

# This is all captured...
puts 'Capturing to buffer...'
pp asdf

# reset STDOUT
$stdout = old_stdout
puts 'Capturing off...'

# show what we got...
puts captured_stdio.string

And what was printed:

Writing to STDOUT...
{"a"=>1, :b=>2, "c"=>["ho", "daddy"]}
Capturing off...
Capturing to buffer...
{"a"=>1, :b=>2, "c"=>["ho", "daddy"]}

The last two lines above were stored in captured_stdio by substituting that for the normal $stdout channel. Anything written to (what would be STDOUT) got stored. Swapping back in the original channel restored normal printing, and stopped anything else from being written to captured_stdio.