Class | Binding |
In: |
lib/binding_of_caller.rb
|
Parent: | Object |
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.
# File lib/binding_of_caller.rb, line 35 35: def Binding.of_caller(&block) 36: old_critical = Thread.critical 37: Thread.critical = true 38: count = 0 39: cc, result, error, extra_data = Continuation.create(nil, nil) 40: error.call if error 41: 42: tracer = lambda do |*args| 43: type, context, extra_data = args[0], args[4], args 44: if type == "return" 45: count += 1 46: # First this method and then calling one will return -- 47: # the trace event of the second event gets the context 48: # of the method which called the method that called this 49: # method. 50: if count == 2 51: # It would be nice if we could restore the trace_func 52: # that was set before we swapped in our own one, but 53: # this is impossible without overloading set_trace_func 54: # in current Ruby. 55: set_trace_func(nil) 56: cc.call(eval("binding", context), nil, extra_data) 57: end 58: elsif type == "line" then 59: nil 60: elsif type == "c-return" and extra_data[3] == :set_trace_func then 61: nil 62: else 63: set_trace_func(nil) 64: error_msg = "Binding.of_caller used in non-method context or " + 65: "trailing statements of method using it aren't in the block." 66: cc.call(nil, lambda { raise(ArgumentError, error_msg) }, nil) 67: end 68: end 69: 70: unless result 71: set_trace_func(tracer) 72: return nil 73: else 74: Thread.critical = old_critical 75: case block.arity 76: when 1 then yield(result) 77: else yield(result, extra_data) 78: end 79: end 80: end