YaST Ruby Bindings

It is part of YaST where you can find more information about YaST and its component system. The Ruby bindings cover only the connection to the component system and provide some Ruby helpers.

It started as an experimental project to allow writting in Ruby, but after a decision to switch from an own language YCP to Ruby, it is a major part of YaST needed by almost all parts. As a relict from the language switch it contains constructs to keep backward compatibility which need a human decision before being removed.

Features

Publish, Import and Include

The connection to the YaST component system has two parts. The first one is the ability to be called from the component system. Clients can be called via WFM (see below ) and modules provide an interface via the publish method, where the type signature is specified. Publish is very similar to dbus interface provision. For more details see inline documentation of Yast::Exportable#publish. If a method is needed only from Ruby, then publish is not needed.

The second part is calling methods from the component system. Clients are called via WFM (see below). Methods from modules are imported with Yast.import, which loads a component and creates a Ruby object in the Yast namespace from it, on which exported methods can be called. Note that if a call is done from Ruby to Ruby, then it is not limited by the component system and its protocol, so all Ruby features can be used.

# how to import a module and call it
require "yast"
Yast.import "IP"
puts Yast::IP.Check4("127.0.0.333")

A relict from the transformation from YCP to Ruby is Yast.include which adds methods from the included class to passed object. It is very similar to Ruby include with the exception that an Include object can include other Include objects and thus there is a special constructor instead of common Ruby included.

Ruby Helpers

Ruby bindings provide a set of various helpers for working with the YaST component system or for making the translation from YCP to Ruby easier. Here is an overview of important provided classes with links to the inline documentation and a short explanation:

• Yast::ArgRef: a class to be used for passing arguments by reference. Works even for Ruby immutable types like Fixnum or Symbol.
• Yast::Builtins: this module contains YCP builtins that need to be simulated in Ruby. For new code it should not be used.
• Yast::Client: a base class for clients in Ruby. It is not strictly required to inherit from it, but it adds useful helpers.
• Yast::Convert: simulates type conversion. Not needed in new code.
• Yast::Exportable: provides the method publish (see above).
• Yast::FunRef: a container used to pass references to methods to the component system.
• Yast::I18n: provides methods used for translations.
• Yast::Module: a base class for YaST modules in Ruby. It is not strictly required to inherit from it, but it adds useful helpers.
• Yast::Ops: this module contains YCP operators that need to be simulated in Ruby. For new code it should not be used.
• Yast::Path: represents the path type from the YCP protocol.
• Yast::SCR: allows usage of SCR component for communication with the Linux system.
• Yast::Term: represents the term type from the YCP protocol. Often used for UI.
• Yast::WFM: allows usage of WFM component. WFM is used for calling clients, and for setting a new SCR instance as the global one.
• Yast::Y2Logger: a Ruby Logger configured to work with the YaST log with proper place to use. The Ruby module Yast::Logger provides easy access via the method log.
• Yast: the namespace itself contains a few helpers to be used. It contains shortcuts and a method for a deep copy of an object.

UI Shortcuts

Yast::UIShortcuts provides shortcuts for UI terms. It is useful to construct dialogs or even popups.

# usage with Term
content = Yast::Term.new(
  :ButtonBox,
  Yast::Term.new(
    :PushButton,
    Yast::Term.new(:id, :ok_button),
    "OK"
  )
  Yast::Term.new(
    :PushButton,
    Yast::Term.new(:id, :cancel_button),
    "Cancel"
  )
)

# usage with shortcuts
include Yast::UIShortcuts
content = ButtonBox(
  PushButton(Id(:ok_button), "OK"),
  PushButton(Id(:cancel_button), "Cancel")
)

Core extensions

The YaST bindings also offers some refinements for standard Ruby classes, inspired by Active Support Core Extensions but making use of Ruby refinements. Those refinements can be used to temporary extend the base classes with handy methods for a variety of uses, like shown in the following example.

require "yast"
require "yast/core_ext"

module Isolated
  using Yast::CoreExt::AnsiString

  string = File.open("ansi.txt", "rb").read
  string.remove_ansi_sequences
  puts "clean string: #{string}"
end

# Out of the module, thus different scope
another_string = "whatever"
another_string.remove_ansi_sequences # => NoMethodError

The following refinements are currently provided:

• Yast::CoreExt::AnsiString: to remove ANSI control sequences from String objects

Testing

The YaST team encourages to use RSpec for testing YaST code in Ruby. To help in that task, this gem includes some RSpec extensions under the Yast::RSpec namespace. In order to use these extensions, the following line must be added to the tests.

require 'yast/rspec'

For example, the following code makes use of the #path helper provided by Yast::RSpec::Shortcuts.

require 'yast/rspec'

describe ".proc.meminfo agent" do
  it "returns a Hash" do
    value = Yast::SCR.Read(path(".proc.meminfo"))
    expect(value).to be_a(Hash)
  end
end

Further Information

More information about YaST can be found on its homepage. More information about Ruby bindings can be found in the generated documentation.

Packager information

How to Compile

Use the latest yast2-devtools, then use these calls:

mkdir build
cd build
cmake ..
make

How to Install

Compile it, and from the build directory call as root:

make install

How to Create a Tarball

rake package

Then the RPM sources are in the package subdirectory.

Exception handling

If Ruby code raises an exception, then the method returns nil to YCP, and the method last_exception returns the message of the exception. Also, exception details are logged.