A Struct is a convenient way to bundle a number of attributes together, using accessor methods, without having to write an explicit class.
The Struct class generates new subclasses that hold a set of members and their values. For each member a reader and writer method is created similar to Module#attr_accessor.
Customer = Struct.new(:name, :address) do def greeting "Hello #{name}!" end end dave = Customer.new("Dave", "123 Main") dave.name #=> "Dave" dave.greeting #=> "Hello Dave!"
See Struct::new for further examples of creating struct subclasses and instances.
In the method descriptions that follow, a “member” parameter refers to a struct member which is either a quoted string ("name") or a Symbol (:name).
An OpenStruct is a data structure, similar to a Hash, that allows the definition of arbitrary attributes with their accompanying values. This is accomplished by using Ruby’s metaprogramming to define methods on the class itself.
require "ostruct" person = OpenStruct.new person.name = "John Smith" person.age = 70 person.name # => "John Smith" person.age # => 70 person.address # => nil
An OpenStruct employs a Hash internally to store the attributes and values and can even be initialized with one:
australia = OpenStruct.new(:country => "Australia", :capital => "Canberra") # => #<OpenStruct country="Australia", capital="Canberra">
Hash keys with spaces or characters that could normally not be used for method calls (e.g. ()[]*) will not be immediately available on the OpenStruct object as a method for retrieval or assignment, but can still be reached through the Object#send method.
measurements = OpenStruct.new("length (in inches)" => 24) measurements.send("length (in inches)") # => 24 message = OpenStruct.new(:queued? => true) message.queued? # => true message.send("queued?=", false) message.queued? # => false
Removing the presence of an attribute requires the execution of the delete_field method as setting the property value to nil will not remove the attribute.
first_pet = OpenStruct.new(:name => "Rowdy", :owner => "John Smith") second_pet = OpenStruct.new(:name => "Rowdy") first_pet.owner = nil first_pet # => #<OpenStruct name="Rowdy", owner=nil> first_pet == second_pet # => false first_pet.delete_field(:owner) first_pet # => #<OpenStruct name="Rowdy"> first_pet == second_pet # => true
An OpenStruct utilizes Ruby’s method lookup structure to find and define the necessary methods for properties. This is accomplished through the methods method_missing and define_singleton_method.
This should be a consideration if there is a concern about the performance of the objects that are created, as there is much more overhead in the setting of these properties compared to using a Hash or a Struct.
The Addrinfo class maps struct addrinfo to ruby. This structure identifies an Internet host and a service.
The Matrix class represents a mathematical matrix. It provides methods for creating matrices, operating on them arithmetically and algebraically, and determining their mathematical properties (trace, rank, inverse, determinant).
Method Catalogue To create a matrix:
Matrix.rows(rows, copy = true)
Matrix.build(row_count, column_count, &block)
To access Matrix elements/columns/rows/submatrices/properties:
laplace_expansion(row_or_column: num)
cofactor_expansion(row_or_column: num)
Properties of a matrix:
Matrix arithmetic:
Matrix functions:
Matrix decompositions:
Complex arithmetic:
conj
conjugate
imag
imaginary
real
rect
rectangular
Conversion to other data types:
String representations:
This class implements a pretty printing algorithm. It finds line breaks and nice indentations for grouped structure.
By default, the class assumes that primitive elements are strings and each byte in the strings have single column in width. But it can be used for other situations by giving suitable arguments for some methods:
newline object and space generation block for PrettyPrint.new
optional width argument for PrettyPrint#text
There are several candidate uses:
text formatting using proportional fonts
multibyte characters which has columns different to number of bytes
non-string formatting
Box based formatting?
Other (better) model/algorithm?
Report any bugs at bugs.ruby-lang.org
Christian Lindig, Strictly Pretty, March 2000, www.st.cs.uni-sb.de/~lindig/papers/#pretty
Philip Wadler, A prettier printer, March 1998, homepages.inf.ed.ac.uk/wadler/topics/language-design.html#prettier
Tanaka Akira <akr@fsij.org>
Raised in case of a stack overflow.
def me_myself_and_i me_myself_and_i end me_myself_and_i
raises the exception:
SystemStackError: stack level too deep
A class that provides the functionality of Kernel#set_trace_func in a nice Object-Oriented API.
We can use TracePoint to gather information specifically for exceptions:
trace = TracePoint.new(:raise) do |tp| p [tp.lineno, tp.event, tp.raised_exception] end #=> #<TracePoint:disabled> trace.enable #=> false 0 / 0 #=> [5, :raise, #<ZeroDivisionError: divided by 0>]
If you don’t specify the type of events you want to listen for, TracePoint will include all available events.
Note do not depend on current event set, as this list is subject to change. Instead, it is recommended you specify the type of events you want to use.
To filter what is traced, you can pass any of the following as events:
:line
execute code on a new line
:class
start a class or module definition
:end
finish a class or module definition
:call
call a Ruby method
:return
return from a Ruby method
:c_call
call a C-language routine
:c_return
return from a C-language routine
:raise
raise an exception
:b_call
event hook at block entry
:b_return
event hook at block ending
:thread_begin
event hook at thread beginning
:thread_end
event hook at thread ending
:fiber_switch
event hook at fiber switch
SingleForwardable can be used to setup delegation at the object level as well.
printer = String.new printer.extend SingleForwardable # prepare object for delegation printer.def_delegator "STDOUT", "puts" # add delegation for STDOUT.puts() printer.puts "Howdy!"
Also, SingleForwardable can be used to set up delegation for a Class or Module.
class Implementation def self.service puts "serviced!" end end module Facade extend SingleForwardable def_delegator :Implementation, :service end Facade.service #=> serviced!
If you want to use both Forwardable and SingleForwardable, you can use methods def_instance_delegator and def_single_delegator, etc.
A module to implement the Linda distributed computing paradigm in Ruby.
See the sample/drb/ directory in the Ruby distribution, from 1.8.2 onwards.
The Singleton module implements the Singleton pattern.
To use Singleton, include the module in your class.
class Klass include Singleton # ... end
This ensures that only one instance of Klass can be created.
a,b = Klass.instance, Klass.instance a == b # => true Klass.new # => NoMethodError - new is private ...
The instance is created at upon the first call of Klass.instance().
class OtherKlass include Singleton # ... end ObjectSpace.each_object(OtherKlass){} # => 0 OtherKlass.instance ObjectSpace.each_object(OtherKlass){} # => 1
This behavior is preserved under inheritance and cloning.
This above is achieved by:
Making Klass.new and Klass.allocate private.
Overriding Klass.inherited(sub_klass) and Klass.clone() to ensure that the Singleton properties are kept when inherited and cloned.
Providing the Klass.instance() method that returns the same object each time it is called.
Overriding Klass._load(str) to call Klass.instance().
Overriding Klass#clone and Klass#dup to raise TypeErrors to prevent cloning or duping.
Singleton and Marshal By default Singleton’s _dump(depth) returns the empty string. Marshalling by default will strip state information, e.g. instance variables and taint state, from the instance. Classes using Singleton can provide custom _load(str) and _dump(depth) methods to retain some of the previous state of the instance.
require 'singleton' class Example include Singleton attr_accessor :keep, :strip def _dump(depth) # this strips the @strip information from the instance Marshal.dump(@keep, depth) end def self._load(str) instance.keep = Marshal.load(str) instance end end a = Example.instance a.keep = "keep this" a.strip = "get rid of this" a.taint stored_state = Marshal.dump(a) a.keep = nil a.strip = nil b = Marshal.load(stored_state) p a == b # => true p a.keep # => "keep this" p a.strip # => nil
A custom InputMethod class used by XMP for evaluating string io.
RingFinger is used by RingServer clients to discover the RingServer’s TupleSpace. Typically, all a client needs to do is call RingFinger.primary to retrieve the remote TupleSpace, which it can then begin using.
To find the first available remote TupleSpace:
Rinda::RingFinger.primary
To create a RingFinger that broadcasts to a custom list:
rf = Rinda::RingFinger.new ['localhost', '192.0.2.1'] rf.primary
Rinda::RingFinger also understands multicast addresses and sets them up properly. This allows you to run multiple RingServers on the same host:
rf = Rinda::RingFinger.new ['239.0.0.1'] rf.primary
You can set the hop count (or TTL) for multicast searches using multicast_hops.
If you use IPv6 multicast you may need to set both an address and the outbound interface index:
rf = Rinda::RingFinger.new ['ff02::1'] rf.multicast_interface = 1 rf.primary
At this time there is no easy way to get an interface index by name.
WIN32OLE_VARIABLE objects represent OLE variable information.
WIN32OLE_VARIANT objects represents OLE variant.
Win32OLE converts Ruby object into OLE variant automatically when invoking OLE methods. If OLE method requires the argument which is different from the variant by automatic conversion of Win32OLE, you can convert the specfied variant type by using WIN32OLE_VARIANT class.
param = WIN32OLE_VARIANT.new(10, WIN32OLE::VARIANT::VT_R4) oleobj.method(param)
WIN32OLE_VARIANT does not support VT_RECORD variant. Use WIN32OLE_RECORD class instead of WIN32OLE_VARIANT if the VT_RECORD variant is needed.
Certain attributes are required on specific tags in an RSS feed. If a feed is missing one of these attributes, a MissingAttributeError is raised.
This exception is raised if the nesting of parsed data structures is too deep.
The InstructionSequence class represents a compiled sequence of instructions for the Ruby Virtual Machine.
With it, you can get a handle to the instructions that make up a method or a proc, compile strings of Ruby code down to VM instructions, and disassemble instruction sequences to strings for easy inspection. It is mostly useful if you want to learn how the Ruby VM works, but it also lets you control various settings for the Ruby iseq compiler.
You can find the source for the VM instructions in insns.def in the Ruby source.
The instruction sequence results will almost certainly change as Ruby changes, so example output in this documentation may be different from what you see.
Exception raised when there is an invalid encoding detected
PrettyPrint::SingleLine is used by PrettyPrint.singleline_format
It is passed to be similar to a PrettyPrint object itself, by responding to:
but instead, the output has no line breaks
An implementation of PseudoPrimeGenerator which uses a prime table generated by trial division.