éncöding hèll (part 3)

12.01.2015 - Pascal Betz

The (currently) last part of my encoding hell series. To finish up I’ll show some samples.

force_encoding and encode

Ruby is smart enough to not encode a string if it is already in the target encoding. This might not be what you want if you have data which has been encoded wrongly in the first place. You can use force_encoding in such cases:

data = "\xF6\xE4\xFC"
p data.encoding
# => "UTF-8"

p data.encode('utf-8')
# => "\xF6\xE4\xFC"

p data.force_encoding('iso-8859-1').encode('utf-8')
# => "öüä"


Data read from a file is expected to be in UTF-8 by default. You can change that using the encoding option. This will lead to Strings that are encoded in something non-UTF-8 though. Ruby offers an easy way to transcode, so you only will have to deal with UTF-8 Strings

data = File.read('file.txt')
puts data.encoding
# => "UTF-8"

data = File.read('file.txt', encoding: 'iso-8859-1')
puts data.encoding
# => "ISO-8859-1"

data = File.read('file.txt', encoding: 'iso-8859-1:utf-8')
puts data.encoding
# => "UTF-8"

String concatenation

This works as long as both Strings are in the same or in a compatible encoding. This can happen in places where you don’t expect it. For example when writing a CSV file or just print out some log information.

utf = "öäü"
iso_1 = utf.encode('iso-8859-1')
iso_2 = "oau".encode('iso-8859-1')
ascii = "oau".encode('ascii')
puts utf + utf
# => öäüöäü
puts utf + iso_1
# => CompatibilityError: incompatible character encodings: UTF-8 and ISO-8859-1
puts utf + iso_2
# => öäüoau
puts utf + ascii
# => öäüoau

puts and p

Ruby calls #inspect when passing an object to p. This leads to some interesting behaviour when printing out Strings of different encodings.

p "öäü".encode('iso-8859-1')
# => "\xF6\xE4\xFC"

puts "öäü".encode('iso-8859-1')
# => ���
# Note: if you run this from Sublime, then you might see the following message:
# [Decode error - output not utf-8]

puts "öäü".encode('iso-8859-1').inspect
# => "\xF6\xE4\xFC"