Results for: "module_function"

Ruby supports two forms of objectified methods. Class Method is used to represent methods that are associated with a particular object: these method objects are bound to that object. Bound method objects for an object can be created using Object#method.

Ruby also supports unbound methods; methods objects that are not associated with a particular object. These can be created either by calling Module#instance_method or by calling unbind on a bound method object. The result of both of these is an UnboundMethod object.

Unbound methods can only be called after they are bound to an object. That object must be a kind_of? the method’s original class.

class Square
  def area
    @side * @side
  end
  def initialize(side)
    @side = side
  end
end

area_un = Square.instance_method(:area)

s = Square.new(12)
area = area_un.bind(s)
area.call   #=> 144

Unbound methods are a reference to the method at the time it was objectified: subsequent changes to the underlying class will not affect the unbound method.

class Test
  def test
    :original
  end
end
um = Test.instance_method(:test)
class Test
  def test
    :modified
  end
end
t = Test.new
t.test            #=> :modified
um.bind(t).call   #=> :original

Response class for Unavailable For Legal Reasons responses (status code 451).

A server operator has received a legal demand to deny access to a resource or to a set of resources that includes the requested resource.

References:

• Mozilla.

• RFC 7725.

• Wikipedia.

Helper methods for both Gem::Installer and Gem::Uninstaller

FIXME: This isn’t documented in Nutshell.

Since MonitorMixin.new_cond returns a ConditionVariable, and the example above calls while_wait and signal, this class should be documented.

Response class for Precondition Failed responses (status code 412).

The server does not meet one of the preconditions specified in the request headers.

References:

• Mozilla.

• RFC 9110.

• Wikipedia.

Response class for Expectation Failed responses (status code 417).

The server cannot meet the requirements of the Expect request-header field.

References:

• Mozilla.

• RFC 9110.

• Wikipedia.

ConditionVariable objects augment class Mutex. Using condition variables, it is possible to suspend while in the middle of a critical section until a condition is met, such as a resource becomes available.

Due to non-deterministic scheduling and spurious wake-ups, users of condition variables should always use a separate boolean predicate (such as reading from a boolean variable) to check if the condition is actually met before starting to wait, and should wait in a loop, re-checking the condition every time the ConditionVariable is waken up. The idiomatic way of using condition variables is calling the wait method in an until loop with the predicate as the loop condition.

condvar.wait(mutex) until condition_is_met

In the example below, we use the boolean variable resource_available (which is protected by mutex) to indicate the availability of the resource, and use condvar to wait for that variable to become true. Note that:

1. Thread b may be scheduled before thread a1 and a2, and may run so fast that it have already made the resource available before either a1 or a2 starts. Therefore, a1 and a2 should check if resource_available is already true before starting to wait.

2. The wait method may spuriously wake up without signalling. Therefore, thread a1 and a2 should recheck resource_available after the wait method returns, and go back to wait if the condition is not actually met.

3. It is possible that thread a2 starts right after thread a1 is waken up by b. Thread a2 may have acquired the mutex and consumed the resource before thread a1 acquires the mutex. This necessitates rechecking after wait, too.

Example:

mutex = Thread::Mutex.new

resource_available = false
condvar = Thread::ConditionVariable.new

a1 = Thread.new {
  # Thread 'a1' waits for the resource to become available and consumes
  # the resource.
  mutex.synchronize {
    condvar.wait(mutex) until resource_available
    # After the loop, 'resource_available' is guaranteed to be true.

    resource_available = false
    puts "a1 consumed the resource"
  }
}

a2 = Thread.new {
  # Thread 'a2' behaves like 'a1'.
  mutex.synchronize {
    condvar.wait(mutex) until resource_available
    resource_available = false
    puts "a2 consumed the resource"
  }
}

b = Thread.new {
  # Thread 'b' periodically makes the resource available.
  loop {
    mutex.synchronize {
      resource_available = true

      # Notify one waiting thread if any.  It is possible that neither
      # 'a1' nor 'a2 is waiting on 'condvar' at this moment.  That's OK.
      condvar.signal
    }
    sleep 1
  }
}

# Eventually both 'a1' and 'a2' will have their resources, albeit in an
# unspecified order.
[a1, a2].each {|th| th.join}

Module that defines the default UserInteraction. Any class including this module will have access to the ui method that returns the default UI.

Potentially raised when a specification is validated.

Represents an error communicating via HTTP.

Raised by Resolver when a dependency requests a gem for which there is no spec.

Keyword completion module. This allows partial arguments to be specified and resolved against a list of acceptable values.

Mixin methods for local and remote Gem::Command options.

An Encoding instance represents a character encoding usable in Ruby. It is defined as a constant under the Encoding namespace. It has a name and, optionally, aliases:

Encoding::US_ASCII.name  # => "US-ASCII"
Encoding::US_ASCII.names # => ["US-ASCII", "ASCII", "ANSI_X3.4-1968", "646"]

A Ruby method that accepts an encoding as an argument will accept:

• An Encoding object.

• The name of an encoding.

• An alias for an encoding name.

These are equivalent:

'foo'.encode(Encoding::US_ASCII) # Encoding object.
'foo'.encode('US-ASCII')         # Encoding name.
'foo'.encode('ASCII')            # Encoding alias.

For a full discussion of encodings and their uses, see the Encodings document.

Encoding::ASCII_8BIT is a special-purpose encoding that is usually used for a string of bytes, not a string of characters. But as the name indicates, its characters in the ASCII range are considered as ASCII characters. This is useful when you use other ASCII-compatible encodings.

Raised when a feature is not implemented on the current platform. For example, methods depending on the fsync or fork system calls may raise this exception if the underlying operating system or Ruby runtime does not support them.

Note that if fork raises a NotImplementedError, then respond_to?(:fork) returns false.