Class Binding
In: vendor/rails/activesupport/lib/active_support/binding_of_caller.rb
Parent: Object

Methods

of_caller  

Public Class methods

This method returns the binding of the method that called your method. It will raise an Exception when you‘re not inside a method.

It‘s used like this:

  def inc_counter(amount = 1)
    Binding.of_caller do |binding|
      # Create a lambda that will increase the variable 'counter'
      # in the caller of this method when called.
      inc = eval("lambda { |arg| counter += arg }", binding)
      # We can refer to amount from inside this block safely.
      inc.call(amount)
    end
    # No other statements can go here. Put them inside the block.
  end
  counter = 0
  2.times { inc_counter }
  counter # => 2

Binding.of_caller must be the last statement in the method. This means that you will have to put everything you want to do after the call to Binding.of_caller into the block of it. This should be no problem however, because Ruby has closures. If you don‘t do this an Exception will be raised. Because of the way that Binding.of_caller is implemented it has to be done this way.

[Source]

    # File vendor/rails/activesupport/lib/active_support/binding_of_caller.rb, line 39
39: def Binding.of_caller(&block)
40:   old_critical = Thread.critical
41:   Thread.critical = true
42:   count = 0
43:   cc, result, error, extra_data = Continuation.create(nil, nil)
44:   error.call if error
45: 
46:   tracer = lambda do |*args|
47:     type, context, extra_data = args[0], args[4], args
48:     if type == "return"
49:       count += 1
50:       # First this method and then calling one will return --

51:       # the trace event of the second event gets the context

52:       # of the method which called the method that called this

53:       # method.

54:       if count == 2
55:         # It would be nice if we could restore the trace_func

56:         # that was set before we swapped in our own one, but

57:         # this is impossible without overloading set_trace_func

58:         # in current Ruby.

59:         set_trace_func(nil)
60:         cc.call(eval("binding", context), nil, extra_data)
61:       end
62:     elsif type == "line" then
63:       nil
64:     elsif type == "c-return" and extra_data[3] == :set_trace_func then
65:       nil
66:     else
67:       set_trace_func(nil)
68:       error_msg = "Binding.of_caller used in non-method context or " +
69:         "trailing statements of method using it aren't in the block."
70:       cc.call(nil, lambda { raise(ArgumentError, error_msg) }, nil)
71:     end
72:   end
73: 
74:   unless result
75:     set_trace_func(tracer)
76:     return nil
77:   else
78:     Thread.critical = old_critical
79:     case block.arity
80:       when 1 then yield(result)
81:       else yield(result, extra_data)        
82:     end
83:   end
84: end

[Validate]