Results for: "Psych"

Tokenize string returning the Ruby object

Create a new TreeBuilder instance

Create a new Psych::Emitter that writes to io.

Emit a scalar with value, anchor, tag, and a plain or quoted string type with style.

See Psych::Handler#scalar

Emit an alias with anchor.

See Psych::Handler#alias

Get the output style, canonical or not.

Set the output style to canonical, or not.

Get the indentation level.

Set the indentation level to level. The level must be less than 10 and greater than 1.

Start streaming using encoding

@api private

Raised by exit to initiate the termination of the script.

Raised when encountering Ruby code with an invalid syntax.

eval("1+1=2")

raises the exception:

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

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

Symbol objects represent named identifiers inside the Ruby interpreter.

You can create a Symbol object explicitly with:

• A symbol literal.

The same Symbol object will be created for a given name or string for the duration of a program’s execution, regardless of the context or meaning of that name. Thus if Fred is a constant in one context, a method in another, and a class in a third, the Symbol :Fred will be the same object in all three contexts.

module One
  class Fred
  end
  $f1 = :Fred
end
module Two
  Fred = 1
  $f2 = :Fred
end
def Fred()
end
$f3 = :Fred
$f1.object_id   #=> 2514190
$f2.object_id   #=> 2514190
$f3.object_id   #=> 2514190

Constant, method, and variable names are returned as symbols:

module One
  Two = 2
  def three; 3 end
  @four = 4
  @@five = 5
  $six = 6
end
seven = 7

One.constants
# => [:Two]
One.instance_methods(true)
# => [:three]
One.instance_variables
# => [:@four]
One.class_variables
# => [:@@five]
global_variables.grep(/six/)
# => [:$six]
local_variables
# => [:seven]

Symbol objects are different from String objects in that Symbol objects represent identifiers, while String objects represent text or data.

What’s Here

First, what’s elsewhere. Class Symbol:

• Inherits from class Object.

• Includes module Comparable.

Here, class Symbol provides methods that are useful for:

• Querying

• Comparing

• Converting

Methods for Querying

• ::all_symbols

  Returns an array of the symbols currently in Ruby’s symbol table.

• #=~

  Returns the index of the first substring in symbol that matches a given Regexp or other object; returns nil if no match is found.

• [], slice

  Returns a substring of symbol determined by a given index, start/length, or range, or string.

• empty?

  Returns true if self.length is zero; false otherwise.

• encoding

  Returns the Encoding object that represents the encoding of symbol.

• end_with?

  Returns true if symbol ends with any of the given strings.

• match

  Returns a MatchData object if symbol matches a given Regexp; nil otherwise.

• match?

  Returns true if symbol matches a given Regexp; false otherwise.

• length, size

  Returns the number of characters in symbol.

• start_with?

  Returns true if symbol starts with any of the given strings.

Methods for Comparing

• #<=>

  Returns -1, 0, or 1 as a given symbol is smaller than, equal to, or larger than symbol.

• #==, #===

  Returns true if a given symbol has the same content and encoding.

• casecmp

  Ignoring case, returns -1, 0, or 1 as a given symbol is smaller than, equal to, or larger than symbol.

• casecmp?

  Returns true if symbol is equal to a given symbol after Unicode case folding; false otherwise.

Methods for Converting

• capitalize

  Returns symbol with the first character upcased and all other characters downcased.

• downcase

  Returns symbol with all characters downcased.

• inspect

  Returns the string representation of self as a symbol literal.

• name

  Returns the frozen string corresponding to symbol.

• succ, next

  Returns the symbol that is the successor to symbol.

• swapcase

  Returns symbol with all upcase characters downcased and all downcase characters upcased.

• to_proc

  Returns a Proc object which responds to the method named by symbol.

• to_s, id2name

  Returns the string corresponding to self.

• to_sym, intern

  Returns self.

• upcase

  Returns symbol with all characters upcased.

IPSocket is the super class of TCPSocket and UDPSocket.