How To...

Use an older version of Tap (or any gem)

Rubygems makes it very easy to use an older version of tap:

% tap _version_ ...

As you can see, all you have to do is specify the version in the first argument. This trick can also be useful for fixing the version of tap used if it gets called from another process.

% tap _0.10.3_
usage: tap  {options} [args]

examples:
  tap generate root .                  # generates a root dir
  tap run taskname --option input      # runs the 'taskname' task

help:
  tap help                             # prints this help
  tap command --help                   # prints help for 'command'

available commands:
  console
  destroy
  generate
  help
  run

version 0.10.3 -- http://tap.rubyforge.org

Install SQLite3

Many of the tap libraries I’ve developed utilize SQLite3 because it is easy to get running. Here are the basic installation instructions.

Install the binaries

On Mac OSX/Unix, sqlite3 is usually pre-installed. Try calling sqlite3 from a command prompt to check (see below). If it isn’t installed, check the {sqlite website}[http://www.sqlite.org/] for installation instructions.

On Windows:

1. Download the sqlite3 command line program and .dll from the {downloads page}[http://www.sqlite.org/download.html]. They will be named like ‘sqlite-3_version.zip’ and ‘sqlitedll-3_version.zip’ respectively.
2. Extract/copy these files (sqlite3.exe and sqlite3.dll) into C:\ruby\bin, or the bin directory of wherever you installed ruby.

Now you should be able to access sqlite3 from a command prompt:

% sqlite3
SQLite version 3.[version]
Enter ".help" for instructions
sqlite>

Install the ruby bindings

% gem install sqlite3-ruby

And that’s it!

Enter newlines, escape characters into configurations

Sometimes you need escaped characters in a configuration, for instance when formatting csv output. To do so, use the string validation then write them in as you would in a script:

# StringConfig::manifest
class StringConfig < Tap::Task
  config :a, "", &c.string
  config :b, "", &c.string
  config :c, "", &c.string
  config :d, "", &c.string
  config :e, "", &c.string

  def process
    [:a,:b,:c,:d,:e].each do |key|
      type = case config[key]
      when "\n" then 'newline'
      when '\n' then 'backslash, n'
      else 'other'
      end

      puts "#{key}: #{type}" 
    end
  end
end

Now check out what happens:

% tap run -- string_config --a '\n' --b '\\n' --c "\n" --d "\\n" --e "\\\n" 
a: newline
b: backslash, n
c: newline
d: newline
e: backslash, n