Results for: "Logger"

Net::HTTPServerError

Parent class for server error (5xx) HTTP response classes.

A server error response indicates that the server failed to fulfill a request.

References:

Net::ProtoServerError

No documentation available

Reline::ConfigEncodingConversionError

No documentation available

Encoding::ConverterNotFoundError

Raised by transcoding methods when a named encoding does not correspond with a known converter.

MakeMakefile::Logging

No documentation available

Gem::BundlerVersionFinder

No documentation available

Numeric

Numeric is the class from which all higher-level numeric classes should inherit.

Numeric allows instantiation of heap-allocated objects. Other core numeric classes such as Integer are implemented as immediates, which means that each Integer is a single immutable object which is always passed by value.

a = 1
1.object_id == a.object_id   #=> true

There can only ever be one instance of the integer 1, for example. Ruby ensures this by preventing instantiation. If duplication is attempted, the same instance is returned.

Integer.new(1)                   #=> NoMethodError: undefined method `new' for Integer:Class
1.dup                            #=> 1
1.object_id == 1.dup.object_id   #=> true

For this reason, Numeric should be used when defining other numeric classes.

Classes which inherit from Numeric must implement coerce, which returns a two-member Array containing an object that has been coerced into an instance of the new class and self (see coerce).

Inheriting classes should also implement arithmetic operator methods (+, -, * and /) and the <=> operator (see Comparable). These methods may rely on coerce to ensure interoperability with instances of other numeric classes.

class Tally < Numeric
  def initialize(string)
    @string = string
  end

  def to_s
    @string
  end

  def to_i
    @string.size
  end

  def coerce(other)
    [self.class.new('|' * other.to_i), self]
  end

  def <=>(other)
    to_i <=> other.to_i
  end

  def +(other)
    self.class.new('|' * (to_i + other.to_i))
  end

  def -(other)
    self.class.new('|' * (to_i - other.to_i))
  end

  def *(other)
    self.class.new('|' * (to_i * other.to_i))
  end

  def /(other)
    self.class.new('|' * (to_i / other.to_i))
  end
end

tally = Tally.new('||')
puts tally * 2            #=> "||||"
puts tally > 1            #=> true

What’s Here

First, what’s elsewhere. Class Numeric:

Here, class Numeric provides methods for:

Querying

Comparing

Converting

Other

Float

A Float object represents a sometimes-inexact real number using the native architecture’s double-precision floating point representation.

Floating point has a different arithmetic and is an inexact number. So you should know its esoteric system. See following:

You can create a Float object explicitly with:

You can convert certain objects to Floats with:

What’s Here

First, what’s elsewhere. Class Float:

Here, class Float provides methods for:

Querying

Comparing

Converting

Fiber

Fibers are primitives for implementing light weight cooperative concurrency in Ruby. Basically they are a means of creating code blocks that can be paused and resumed, much like threads. The main difference is that they are never preempted and that the scheduling must be done by the programmer and not the VM.

As opposed to other stackless light weight concurrency models, each fiber comes with a stack. This enables the fiber to be paused from deeply nested function calls within the fiber block. See the ruby(1) manpage to configure the size of the fiber stack(s).

When a fiber is created it will not run automatically. Rather it must be explicitly asked to run using the Fiber#resume method. The code running inside the fiber can give up control by calling Fiber.yield in which case it yields control back to caller (the caller of the Fiber#resume).

Upon yielding or termination the Fiber returns the value of the last executed expression

For instance:

fiber = Fiber.new do
  Fiber.yield 1
  2
end

puts fiber.resume
puts fiber.resume
puts fiber.resume

produces

1
2
FiberError: dead fiber called

The Fiber#resume method accepts an arbitrary number of parameters, if it is the first call to resume then they will be passed as block arguments. Otherwise they will be the return value of the call to Fiber.yield

Example:

fiber = Fiber.new do |first|
  second = Fiber.yield first + 2
end

puts fiber.resume 10
puts fiber.resume 1_000_000
puts fiber.resume "The fiber will be dead before I can cause trouble"

produces

12
1000000
FiberError: dead fiber called

Non-blocking Fibers

The concept of non-blocking fiber was introduced in Ruby 3.0. A non-blocking fiber, when reaching a operation that would normally block the fiber (like sleep, or wait for another process or I/O) will yield control to other fibers and allow the scheduler to handle blocking and waking up (resuming) this fiber when it can proceed.

For a Fiber to behave as non-blocking, it need to be created in Fiber.new with blocking: false (which is the default), and Fiber.scheduler should be set with Fiber.set_scheduler. If Fiber.scheduler is not set in the current thread, blocking and non-blocking fibers’ behavior is identical.

Ruby doesn’t provide a scheduler class: it is expected to be implemented by the user and correspond to Fiber::Scheduler.

There is also Fiber.schedule method, which is expected to immediately perform the given block in a non-blocking manner. Its actual implementation is up to the scheduler.

Enumerator

A class which allows both internal and external iteration.

An Enumerator can be created by the following methods.

Most methods have two forms: a block form where the contents are evaluated for each item in the enumeration, and a non-block form which returns a new Enumerator wrapping the iteration.

enumerator = %w(one two three).each
puts enumerator.class # => Enumerator

enumerator.each_with_object("foo") do |item, obj|
  puts "#{obj}: #{item}"
end

# foo: one
# foo: two
# foo: three

enum_with_obj = enumerator.each_with_object("foo")
puts enum_with_obj.class # => Enumerator

enum_with_obj.each do |item, obj|
  puts "#{obj}: #{item}"
end

# foo: one
# foo: two
# foo: three

This allows you to chain Enumerators together. For example, you can map a list’s elements to strings containing the index and the element as a string via:

puts %w[foo bar baz].map.with_index { |w, i| "#{i}:#{w}" }
# => ["0:foo", "1:bar", "2:baz"]

External Iteration

An Enumerator can also be used as an external iterator. For example, Enumerator#next returns the next value of the iterator or raises StopIteration if the Enumerator is at the end.

e = [1,2,3].each   # returns an enumerator object.
puts e.next   # => 1
puts e.next   # => 2
puts e.next   # => 3
puts e.next   # raises StopIteration

next, next_values, peek, and peek_values are the only methods which use external iteration (and Array#zip(Enumerable-not-Array) which uses next internally).

These methods do not affect other internal enumeration methods, unless the underlying iteration method itself has side-effect, e.g. IO#each_line.

FrozenError will be raised if these methods are called against a frozen enumerator. Since rewind and feed also change state for external iteration, these methods may raise FrozenError too.

External iteration differs significantly from internal iteration due to using a Fiber:

Concretely:

Thread.current[:fiber_local] = 1
Fiber[:storage_var] = 1
e = Enumerator.new do |y|
  p Thread.current[:fiber_local] # for external iteration: nil, for internal iteration: 1
  p Fiber[:storage_var] # => 1, inherited
  Fiber[:storage_var] += 1
  y << 42
end

p e.next # => 42
p Fiber[:storage_var] # => 1 (it ran in a different Fiber)

e.each { p _1 }
p Fiber[:storage_var] # => 2 (it ran in the same Fiber/"stack" as the current Fiber)

Convert External Iteration to Internal Iteration

You can use an external iterator to implement an internal iterator as follows:

def ext_each(e)
  while true
    begin
      vs = e.next_values
    rescue StopIteration
      return $!.result
    end
    y = yield(*vs)
    e.feed y
  end
end

o = Object.new

def o.each
  puts yield
  puts yield(1)
  puts yield(1, 2)
  3
end

# use o.each as an internal iterator directly.
puts o.each {|*x| puts x; [:b, *x] }
# => [], [:b], [1], [:b, 1], [1, 2], [:b, 1, 2], 3

# convert o.each to an external iterator for
# implementing an internal iterator.
puts ext_each(o.to_enum) {|*x| puts x; [:b, *x] }
# => [], [:b], [1], [:b, 1], [1, 2], [:b, 1, 2], 3

StopIteration

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!

Interrupt

Raised when the interrupt signal is received, typically because the user has pressed Control-C (on most posix platforms). As such, it is a subclass of SignalException.

begin
  puts "Press ctrl-C when you get bored"
  loop {}
rescue Interrupt => e
  puts "Note: You will typically use Signal.trap instead."
end

produces:

Press ctrl-C when you get bored

then waits until it is interrupted with Control-C and then prints:

Note: You will typically use Signal.trap instead.

StandardError

The most standard error types are subclasses of StandardError. A rescue clause without an explicit Exception class will rescue all StandardErrors (and only those).

def foo
  raise "Oups"
end
foo rescue "Hello"   #=> "Hello"

On the other hand:

require 'does/not/exist' rescue "Hi"

raises the exception:

LoadError: no such file to load -- does/not/exist

TypeError

Raised when encountering an object that is not of the expected type.

[1, 2, 3].first("two")

raises the exception:

TypeError: no implicit conversion of String into Integer

ArgumentError

Raised when the arguments are wrong and there isn’t a more specific Exception class.

Ex: passing the wrong number of arguments

[1, 2, 3].first(4, 5)

raises the exception:

ArgumentError: wrong number of arguments (given 2, expected 1)

Ex: passing an argument that is not acceptable:

[1, 2, 3].first(-4)

raises the exception:

ArgumentError: negative array size

IndexError

Raised when the given index is invalid.

a = [:foo, :bar]
a.fetch(0)   #=> :foo
a[4]         #=> nil
a.fetch(4)   #=> IndexError: index 4 outside of array bounds: -2...2

KeyError

Raised when the specified key is not found. It is a subclass of IndexError.

h = {"foo" => :bar}
h.fetch("foo") #=> :bar
h.fetch("baz") #=> KeyError: key not found: "baz"

ScriptError

ScriptError is the superclass for errors raised when a script can not be executed because of a LoadError, NotImplementedError or a SyntaxError. Note these type of ScriptErrors are not StandardError and will not be rescued unless it is specified explicitly (or its ancestor Exception).

SyntaxError

Raised when encountering Ruby code with an invalid syntax.

eval("1+1=2")

raises the exception:

SyntaxError: (eval):1: syntax error, unexpected '=', expecting $end

NotImplementedError

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.

NameError

Raised when a given name is invalid or undefined.

puts foo

raises the exception:

NameError: undefined local variable or method `foo' for main:Object

Since constant names must start with a capital:

Integer.const_set :answer, 42

raises the exception:

NameError: wrong constant name answer

NoMethodError

Raised when a method is called on a receiver which doesn’t have it defined and also fails to respond with method_missing.

"hello".to_ary

raises the exception:

NoMethodError: undefined method `to_ary' for an instance of String

RuntimeError

A generic error class raised when an invalid operation is attempted. Kernel#raise will raise a RuntimeError if no Exception class is specified.

raise "ouch"

raises the exception:

RuntimeError: ouch

FrozenError

Raised when there is an attempt to modify a frozen object.

[1, 2, 3].freeze << 4

raises the exception:

FrozenError: can't modify frozen Array

SecurityError

No longer used by internal code.

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