Programming Ruby

The Pragmatic Programmer's Guide

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class Binding
Parent: Object
Version: 1.6


Objects of class Binding encapsulate the execution context at some particular place in the code and retain this context for future use. The variables, methods, value of self, and possibly an iterator block that can be accessed in this context are all retained. Binding objects can be created using Kernel#binding , and are made available to the callback of Kernel#set_trace_func .

These binding objects can be passed as the second argument of the Kernel#eval method, establishing an environment for the evaluation.

class Demo
  def initialize(n)
    @secret = n
  def getBinding
    return binding()
k1 =
b1 = k1.getBinding
k2 =
b2 = k2.getBinding
eval("@secret", b1) 99
eval("@secret", b2) -3
eval("@secret") nil

Binding objects have no class-specific methods.

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Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2001 by Addison Wesley Longman, Inc. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at

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