Datasets:
gadams
/
ruby

Dataset card Data Studio Files
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begin
# a blind rescue rescues from StandardError, not Exception as many
# programmers assume.
rescue => e
# exception handling
end
# also good
begin
# an exception occurs here
rescue StandardError => e
# exception handling
end
----
=== Exception Rescuing Ordering [[exception-ordering]]
Put more specific exceptions higher up the rescue chain, otherwise they'll never be rescued from.
[source,ruby]
----
# bad
begin
# some code
rescue StandardError => e
# some handling
rescue IOError => e
# some handling that will never be executed
end
# good
begin
# some code
rescue IOError => e
# some handling
rescue StandardError => e
# some handling
end
----
=== Reading from a file [[file-read]]
Use the convenience methods `File.read` or `File.binread` when only reading a file start to finish in a single operation.
[source,ruby]
----
## text mode
# bad (only when reading from beginning to end - modes: 'r', 'rt', 'r+', 'r+t')
File.open(filename).read
File.open(filename, &:read)
File.open(filename) { |f| f.read }
File.open(filename) do |f|
f.read
end
File.open(filename, 'r').read
File.open(filename, 'r', &:read)
File.open(filename, 'r') { |f| f.read }
File.open(filename, 'r') do |f|
f.read
end
# good
File.read(filename)
## binary mode
# bad (only when reading from beginning to end - modes: 'rb', 'r+b')
File.open(filename, 'rb').read
File.open(filename, 'rb', &:read)
File.open(filename, 'rb') { |f| f.read }
File.open(filename, 'rb') do |f|
f.read
end
# good
File.binread(filename)
----
=== Writing to a file [[file-write]]
Use the convenience methods `File.write` or `File.binwrite` when only opening a file to create / replace its content in a single operation.
[source,ruby]
----
## text mode
# bad (only truncating modes: 'w', 'wt', 'w+', 'w+t')
File.open(filename, 'w').write(content)
File.open(filename, 'w') { |f| f.write(content) }
File.open(filename, 'w') do |f|
f.write(content)
end
# good
File.write(filename, content)
## binary mode
# bad (only truncating modes: 'wb', 'w+b')
File.open(filename, 'wb').write(content)
File.open(filename, 'wb') { |f| f.write(content) }
File.open(filename, 'wb') do |f|
f.write(content)