Results for: "to_proc"

Returns a Ruby lighter-weight code representation of this specification, used for indexing only.

See to_ruby.

Raised when an invalid operation is attempted on a Fiber, in particular when attempting to call/resume a dead fiber, attempting to yield from the root fiber, or calling a fiber across threads.

fiber = Fiber.new{}
fiber.resume #=> nil
fiber.resume #=> FiberError: dead fiber called

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

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

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

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

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"

Raised when a given numerical value is out of range.

[1, 2, 3].drop(1 << 100)

raises the exception:

RangeError: bignum too big to convert into `long'

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).

Raised when encountering Ruby code with an invalid syntax.

eval("1+1=2")

raises the exception:

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

Raised when a file required (a Ruby script, extension library, …) fails to load.

require 'this/file/does/not/exist'

raises the exception:

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

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.

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

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 "hello":String

A generic error class raised when an invalid operation is attempted.

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

raises the exception:

RuntimeError: can't modify frozen Array

Kernel.raise will raise a RuntimeError if no Exception class is specified.

raise "ouch"

raises the exception:

RuntimeError: ouch

Raised when attempting a potential unsafe operation, typically when the $SAFE level is raised above 0.

foo = "bar"
proc = Proc.new do
  $SAFE = 3
  foo.untaint
end
proc.call

raises the exception:

SecurityError: Insecure: Insecure operation `untaint' at level 3

Raised when memory allocation fails.

EncodingError is the base class for encoding errors.

SystemCallError is the base class for all low-level platform-dependent errors.

The errors available on the current platform are subclasses of SystemCallError and are defined in the Errno module.

File.open("does/not/exist")

raises the exception:

Errno::ENOENT: No such file or directory - does/not/exist

Exception class used to return errors from the dbm library.

Exception class used to return errors from the sdbm library.

Class Socket provides access to the underlying operating system socket implementations. It can be used to provide more operating system specific functionality than the protocol-specific socket classes.

The constants defined under Socket::Constants are also defined under Socket. For example, Socket::AF_INET is usable as well as Socket::Constants::AF_INET. See Socket::Constants for the list of constants.

What’s a socket?

Sockets are endpoints of a bidirectional communication channel. Sockets can communicate within a process, between processes on the same machine or between different machines. There are many types of socket: TCPSocket, UDPSocket or UNIXSocket for example.

Sockets have their own vocabulary:

domain: The family of protocols:

• Socket::PF_INET

• Socket::PF_INET6

• Socket::PF_UNIX

• etc.

type: The type of communications between the two endpoints, typically

• Socket::SOCK_STREAM

• Socket::SOCK_DGRAM.

protocol: Typically zero. This may be used to identify a variant of a protocol.

hostname: The identifier of a network interface:

• a string (hostname, IPv4 or IPv6 address or broadcast which specifies a broadcast address)

• a zero-length string which specifies INADDR_ANY

• an integer (interpreted as binary address in host byte order).

Quick start

Many of the classes, such as TCPSocket, UDPSocket or UNIXSocket, ease the use of sockets comparatively to the equivalent C programming interface.

Let’s create an internet socket using the IPv4 protocol in a C-like manner:

require 'socket'

s = Socket.new Socket::AF_INET, Socket::SOCK_STREAM
s.connect Socket.pack_sockaddr_in(80, 'example.com')

You could also use the TCPSocket class:

s = TCPSocket.new 'example.com', 80

A simple server might look like this:

require 'socket'

server = TCPServer.new 2000 # Server bound to port 2000

loop do
  client = server.accept    # Wait for a client to connect
  client.puts "Hello !"
  client.puts "Time is #{Time.now}"
  client.close
end

A simple client may look like this:

require 'socket'

s = TCPSocket.new 'localhost', 2000

while line = s.gets # Read lines from socket
  puts line         # and print them
end

s.close             # close socket when done

Exception Handling

Ruby’s Socket implementation raises exceptions based on the error generated by the system dependent implementation. This is why the methods are documented in a way that isolate Unix-based system exceptions from Windows based exceptions. If more information on a particular exception is needed, please refer to the Unix manual pages or the Windows WinSock reference.

Convenience methods

Although the general way to create socket is Socket.new, there are several methods of socket creation for most cases.

TCP client socket

Socket.tcp, TCPSocket.open

TCP server socket

Socket.tcp_server_loop, TCPServer.open

UNIX client socket

Socket.unix, UNIXSocket.open

UNIX server socket

Socket.unix_server_loop, UNIXServer.open

Documentation by

• Zach Dennis

• Sam Roberts

• Programming Ruby from The Pragmatic Bookshelf.

Much material in this documentation is taken with permission from Programming Ruby from The Pragmatic Bookshelf.

BasicSocket is the super class for all the Socket classes.