Class: Binding

Inherits:
Object show all
Defined in:
proc.c

Overview

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
  end
  def get_binding
    return binding()
  end
end

k1 = Demo.new(99)
b1 = k1.get_binding
k2 = Demo.new(-3)
b2 = k2.get_binding

eval("@secret", b1)   #=> 99
eval("@secret", b2)   #=> -3
eval("@secret")       #=> nil

Binding objects have no class-specific methods.

Instance Method Summary collapse

Instance Method Details

#clone ⇒ Object

:nodoc:



296
297
298
299
300
301
302
 
# File 'proc.c', line 296

static VALUE
binding_clone(VALUE self)
{
    VALUE bindval = binding_dup(self);
    CLONESETUP(bindval, self);
    return bindval;
}

#dup ⇒ Object

:nodoc:



281
282
283
284
285
286
287
288
289
290
291
292
293
 
# File 'proc.c', line 281

static VALUE
binding_dup(VALUE self)
{
    VALUE bindval = rb_binding_alloc(rb_cBinding);
    rb_binding_t *src, *dst;
    GetBindingPtr(self, src);
    GetBindingPtr(bindval, dst);
    dst->env = src->env;
    dst->path = src->path;
    dst->blockprocval = src->blockprocval;
    dst->first_lineno = src->first_lineno;
    return bindval;
}

#eval(string[, filename [,lineno]]) ⇒ Object

Evaluates the Ruby expression(s) in string, in the binding’s context. If the optional filename and lineno parameters are present, they will be used when reporting syntax errors.

def get_binding(param)
  return binding
end
b = get_binding("hello")
b.eval("param")   #=> "hello"

Returns:



349
350
351
352
353
354
355
356
357
 
# File 'proc.c', line 349

static VALUE
bind_eval(int argc, VALUE *argv, VALUE bindval)
{
    VALUE args[4];

    rb_scan_args(argc, argv, "12", &args[0], &args[2], &args[3]);
    args[1] = bindval;
    return rb_f_eval(argc+1, args, Qnil /* self will be searched in eval */);
}

#local_variable_defined?(symbol) ⇒ Object

Returns a true if a local variable symbol exists.

def foo a = 1 binding.local_variable_defined?(:a) #=> true binding.local_variable_defined?(:b) #=> false end

This method is short version of the following code.

binding.eval(“defined?(#symbol) == ‘local-variable’”)

Returns:

Returns:

  • (Boolean) 


532
533
534
535
536
537
538
539
540
541
542
 
# File 'proc.c', line 532

static VALUE
bind_local_variable_defined_p(VALUE bindval, VALUE sym)
{
    ID lid = check_local_id(bindval, &sym);
    const rb_binding_t *bind;

    if (!lid) return Qfalse;

    GetBindingPtr(bindval, bind);
    return get_local_variable_ptr(bind->env, lid) ? Qtrue : Qfalse;
}

#local_variable_get(symbol) ⇒ Object

Returns a value of local variable symbol.

def foo a = 1 binding.local_variable_get(:a) #=> 1 binding.local_variable_get(:b) #=> NameError end

This method is short version of the following code.

binding.eval(“#symbol”)

Returns:



451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
 
# File 'proc.c', line 451

static VALUE
bind_local_variable_get(VALUE bindval, VALUE sym)
{
    ID lid = check_local_id(bindval, &sym);
    const rb_binding_t *bind;
    const VALUE *ptr;

    if (!lid) goto undefined;

    GetBindingPtr(bindval, bind);

    if ((ptr = get_local_variable_ptr(bind->env, lid)) == NULL) {
      undefined:
	rb_name_error_str(sym, "local variable `%"PRIsVALUE"' not defined for %"PRIsVALUE,
			  sym, bindval);
    }

    return *ptr;
}

#local_variable_set(symbol, obj) ⇒ Object

Set local variable named symbol as obj.

def foo a = 1 b = binding b.local_variable_set(:a, 2) # set existing local variable ‘a’ b.local_variable_set(:b, 3) # create new local variable ‘b’ # ‘b’ exists only in binding. b.local_variable_get(:a) #=> 2 b.local_variable_get(:b) #=> 3 p a #=> 2 p b #=> NameError end

This method is a similar behavior of the following code

binding.eval("#{symbol} = #{obj}")

if obj can be dumped in Ruby code.

Returns:



495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
 
# File 'proc.c', line 495

static VALUE
bind_local_variable_set(VALUE bindval, VALUE sym, VALUE val)
{
    ID lid = check_local_id(bindval, &sym);
    rb_binding_t *bind;
    VALUE *ptr;

    if (!lid) lid = rb_intern_str(sym);

    GetBindingPtr(bindval, bind);
    if ((ptr = get_local_variable_ptr(bind->env, lid)) == NULL) {
	/* not found. create new env */
	ptr = rb_binding_add_dynavars(bind, 1, &lid);
    }

    *ptr = val;

    return val;
}

#local_variables ⇒ Array

Returns the symbol names of the binding’s local variables

def foo a = 1 2.times do |n| binding.local_variables #=> [:a, :n] end end

This method is short version of the following code.

binding.eval(“local_variables”)

Returns:



425
426
427
428
429
430
431
432
 
# File 'proc.c', line 425

static VALUE
bind_local_variables(VALUE bindval)
{
    const rb_binding_t *bind;

    GetBindingPtr(bindval, bind);
    return rb_vm_env_local_variables(bind->env);
}

#receiver ⇒ Object

Returns the bound receiver of the binding object.

Returns:



550
551
552
553
554
555
556
557
558
559
 
# File 'proc.c', line 550

static VALUE
bind_receiver(VALUE bindval)
{
    const rb_binding_t *bind;
    const rb_env_t *env;

    GetBindingPtr(bindval, bind);
    GetEnvPtr(bind->env, env);
    return env->block.self;
}