Results for: "module_function"

If you add a method, keep in mind two things: (1) the first argument will always be a list of nodes from which to filter. In the case of context methods (such as position), the function should return an array with a value for each child in the array. (2) all method calls from XML will have “-” replaced with “_”. Therefore, in XML, “local-name()” is identical (and actually becomes) “local_name()”

An OpenSSL::OCSP::SingleResponse represents an OCSP SingleResponse structure, which contains the basic information of the status of the certificate.

Raised when encoding is invalid.

Indicates that the DNS request was unable to be encoded.

AbstractServlet allows HTTP server modules to be reused across multiple servers and allows encapsulation of functionality.

By default a servlet will respond to GET, HEAD (through an alias to GET) and OPTIONS requests.

By default a new servlet is initialized for every request. A servlet instance can be reused by overriding ::get_instance in the AbstractServlet subclass.

A Simple Servlet

class Simple < WEBrick::HTTPServlet::AbstractServlet
  def do_GET request, response
    status, content_type, body = do_stuff_with request

    response.status = status
    response['Content-Type'] = content_type
    response.body = body
  end

  def do_stuff_with request
    return 200, 'text/plain', 'you got a page'
  end
end

This servlet can be mounted on a server at a given path:

server.mount '/simple', Simple

Servlet Configuration

Servlets can be configured via initialize. The first argument is the HTTP server the servlet is being initialized for.

class Configurable < Simple
  def initialize server, color, size
    super server
    @color = color
    @size = size
  end

  def do_stuff_with request
    content = "<p " \
              %q{style="color: #{@color}; font-size: #{@size}"} \
              ">Hello, World!"

    return 200, "text/html", content
  end
end

This servlet must be provided two arguments at mount time:

server.mount '/configurable', Configurable, 'red', '2em'

Class used to manage timeout handlers across multiple threads.

Timeout handlers should be managed by using the class methods which are synchronized.

id = TimeoutHandler.register(10, Timeout::Error)
begin
  sleep 20
  puts 'foo'
ensure
  TimeoutHandler.cancel(id)
end

will raise Timeout::Error

id = TimeoutHandler.register(10, Timeout::Error)
begin
  sleep 5
  puts 'foo'
ensure
  TimeoutHandler.cancel(id)
end

will print ‘foo’

TextConstruct that conveys a description or subtitle for a Feed.

Reference: validator.w3.org/feed/docs/rfc4287.html#element.subtitle

TextConstruct that conveys a description or title for a Feed or Entry.

Reference: validator.w3.org/feed/docs/rfc4287.html#element.title

An error caused by attempting to fulfil a dependency that was circular

@note This exception will be thrown iff a {Vertex} is added to a

{DependencyGraph} that has a {DependencyGraph::Vertex#path_to?} an
existing {DependencyGraph::Vertex}

Continuation objects are generated by Kernel#callcc, after having +require+d continuation. They hold a return address and execution context, allowing a nonlocal return to the end of the callcc block from anywhere within a program. Continuations are somewhat analogous to a structured version of C’s setjmp/longjmp (although they contain more state, so you might consider them closer to threads).

For instance:

require "continuation"
arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ]
callcc{|cc| $cc = cc}
puts(message = arr.shift)
$cc.call unless message =~ /Max/

produces:

Freddie
Herbie
Ron
Max

Also you can call callcc in other methods:

require "continuation"

def g
  arr = [ "Freddie", "Herbie", "Ron", "Max", "Ringo" ]
  cc = callcc { |cc| cc }
  puts arr.shift
  return cc, arr.size
end

def f
  c, size = g
  c.call(c) if size > 1
end

f

This (somewhat contrived) example allows the inner loop to abandon processing early:

require "continuation"
callcc {|cont|
  for i in 0..4
    print "#{i}: "
    for j in i*5...(i+1)*5
      cont.call() if j == 17
      printf "%3d", j
    end
  end
}
puts

produces:

0:   0  1  2  3  4
1:   5  6  7  8  9
2:  10 11 12 13 14
3:  15 16

Raised to stop the iteration, in particular by Enumerator#next. It is rescued by Kernel#loop.

loop do
  puts "Hello"
  raise StopIteration
  puts "World"
end
puts "Done!"

produces:

Hello
Done!

Class Exception and its subclasses are used to communicate between Kernel#raise and rescue statements in begin ... end blocks.

An Exception object carries information about an exception:

• Its type (the exception’s class).

• An optional descriptive message.

• Optional backtrace information.

Some built-in subclasses of Exception have additional methods: e.g., NameError#name.

Defaults

Two Ruby statements have default exception classes:

• raise: defaults to RuntimeError.

• rescue: defaults to StandardError.

Global Variables

When an exception has been raised but not yet handled (in rescue, ensure, at_exit and END blocks), two global variables are set:

• $! contains the current exception.

• $@ contains its backtrace.

Custom Exceptions

To provide additional or alternate information, a program may create custom exception classes that derive from the built-in exception classes.

A good practice is for a library to create a single “generic” exception class (typically a subclass of StandardError or RuntimeError) and have its other exception classes derive from that class. This allows the user to rescue the generic exception, thus catching all exceptions the library may raise even if future versions of the library add new exception subclasses.

For example:

class MyLibrary
  class Error < ::StandardError
  end

  class WidgetError < Error
  end

  class FrobError < Error
  end

end

To handle both MyLibrary::WidgetError and MyLibrary::FrobError the library user can rescue MyLibrary::Error.

Built-In Exception Classes

The built-in subclasses of Exception are:

• NoMemoryError

• ScriptError

  • LoadError

  • NotImplementedError

  • SyntaxError

• SecurityError

• SignalException

  • Interrupt

• StandardError

  • ArgumentError

    • UncaughtThrowError

  • EncodingError

  • FiberError

  • IOError

    • EOFError

  • IndexError

    • KeyError

    • StopIteration

      • ClosedQueueError

  • LocalJumpError

  • NameError

    • NoMethodError

  • RangeError

    • FloatDomainError

  • RegexpError

  • RuntimeError

    • FrozenError

  • SystemCallError

    • Errno::*

  • ThreadError

  • TypeError

  • ZeroDivisionError

• SystemExit

• SystemStackError

• fatal

A rational number can be represented as a pair of integer numbers: a/b (b>0), where a is the numerator and b is the denominator. Integer a equals rational a/1 mathematically.

In Ruby, you can create rational objects with the Kernel#Rational, to_r, or rationalize methods or by suffixing r to a literal. The return values will be irreducible fractions.

Rational(1)      #=> (1/1)
Rational(2, 3)   #=> (2/3)
Rational(4, -6)  #=> (-2/3)
3.to_r           #=> (3/1)
2/3r             #=> (2/3)

You can also create rational objects from floating-point numbers or strings.

Rational(0.3)    #=> (5404319552844595/18014398509481984)
Rational('0.3')  #=> (3/10)
Rational('2/3')  #=> (2/3)

0.3.to_r         #=> (5404319552844595/18014398509481984)
'0.3'.to_r       #=> (3/10)
'2/3'.to_r       #=> (2/3)
0.3.rationalize  #=> (3/10)

A rational object is an exact number, which helps you to write programs without any rounding errors.

10.times.inject(0) {|t| t + 0.1 }              #=> 0.9999999999999999
10.times.inject(0) {|t| t + Rational('0.1') }  #=> (1/1)

However, when an expression includes an inexact component (numerical value or operation), it will produce an inexact result.

Rational(10) / 3   #=> (10/3)
Rational(10) / 3.0 #=> 3.3333333333333335

Rational(-8) ** Rational(1, 3)
                   #=> (1.0000000000000002+1.7320508075688772i)

Raised when a command was found, but not invoked properly.