Ruby Code Snippets

Useful snippets of Ruby code.

Syntactic Sugar: “with”

###################################################
# Tim Burk's Syntactic Sugar: "with"
#
def with(x)
  yield x if block_given?
  x
end

# ex:
#   button = with(complex Button.new expression) do |b|
#     b.setSize  ...
#     b.setText  ...
#     b.setColor ...
#   end

Auto-require All .rb Files in a Folder

###################################################
# Tim Burk's Auto-require all .rb files in a directory
# 
# Tim wrote:
# >  Here's a code excerpt that does the job.  Just give it a
# >  directory and it will add it to the ruby load path # > ($:.push)
# >  and then require all the .rb files in the directory.  It
# >  also subtracts out the current file so that it can be in the
# >  same directory as the others and not get required twice.
#
def require_all_files(path)
  $:.push path          # resource path
  rbfiles = Dir.entries(path).select {|x| /\.rb\z/ =~ x}
  rbfiles -= [ File.basename(__FILE__) ]
  rbfiles.each do |path|
    require( File.basename(path) )
  end
end

Process Each Line in a File, Skipping Comments

###################################################
# Standard line processing from PickAxe
# 
while gets
  next if /^#/            # Skip comments
  parseLine unless /^$/   # Don't parse empty lines
end

def parseLine
  ...
end

Grep Method on an Enumerable (like a File)

###################################################
# Grep method in enumerable
# 
File.open("ordinal").grep /d$/ do |line|
  print line
end

Implementing “each”

###################################################
# Implementing "each"
# From the Ruby Quick Ref at
# http://www.zenspider.com/Languages/Ruby/QuickRef.html
# 
# By defining the method #each and including Enumerable, you 
# get to use all the methods in Enumerable:
# 
class Mailbox
  include Enumerable
  # ...
  def each
    @mail.each do
       # ...
       yield
    end
  end
end

I/O idioms

###################################################
# I/O Idioms
# 
ARGF.read()
  # --get a string containing concatenated contents
  #    of all files specified on command line, or
   #  obtained from standard input

ARGF.readlines()
  # --get an array

Note:
  # --a reference to ARGF "swallows" the command line
  #   arguments, so they are no longer available

Fixing “Insecure writable dir” Error

###################################################
# Warning: Insecure writable dir (workaround)
# -------------------------------------------
# Some things cause ruby to interact with the
# environment in ways that cause a message to be
# generated:
#
#   warning: Insecure world writable dir
# 
# In my case, I have directories containing
# development tools that, for reasons unknown,
# have a world-writable parent directory. It's
# not something I can change, so I have to find
# ways to suppress the warning.
# 
#   `ls *.rb`     # No warning for this
#   `ls`          # Generates the warning
#   `eval ""; ls` # Workaround to kill the warning
# 
#   path = ENV["PATH"] # Warning for this, too

Search Contents of Files

###################################################
# Search contents of files
#
Dir['**/*.html'].each do |path|
  File.open( path ) do |f|
    f.grep( /search_string/ ) do |line|
      puts path, ': ', line
    end
  end
end

Access Shell-style Utilities

###################################################
# Access shell-style utilities
#
require 'fileutils' # for cd, pwd, mkdir_p, rm_rf, etc.

# for help: ri FileUtils (h,q)

List Files in a Directory

###################################################
# LIST FILES IN A DIRECTORY
#
files = Dir.chdir('lib') { Dir['**/*.rb'] }

Find the site_lib folder

###################################################
# Find the site_lib dir for this version of Ruby
# Cannibalized from the Rake's install.rb which is
# much more robust.
#   => /RUBY_DIR/lib/ruby/site_ruby/1.8
#
require 'rbconfig'
include Config

version = CONFIG["MAJOR"]+"."+CONFIG["MINOR"]
SITE_LIB =
  File.join(CONFIG["libdir"], "ruby", "site_ruby", version)

#usage:
#  INSTALL_DIR = "#{SITE_LIB}/dev"

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