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Class: Binding

Relationships & Source Files
Inherits: Object
Defined in: proc.c,
prelude.rb

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 and instances of ::TracePoint.

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
    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

Instance Method Details

#clone

This method is for internal use only.
[ GitHub ] 

  


# File 'proc.c', line 355



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


  








  

    #dup  
  

  

    This method is for internal use only.
  

  [ GitHub ]


  

  


# File 'proc.c', line 341



static VALUE
binding_dup(VALUE self)
{
    VALUE bindval = rb_binding_alloc(rb_cBinding);
    rb_binding_t *src, *dst;
    GetBindingPtr(self, src);
    GetBindingPtr(bindval, dst);
    rb_vm_block_copy(bindval, &dst->block, &src->block);
    RB_OBJ_WRITE(bindval, &dst->pathobj, src->pathobj);
    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)
  binding
end
b = get_binding("hello")
b.eval("param")   #=> "hello"


  



  [ GitHub ]


  

  


# File 'proc.c', line 408



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 */);
}


  








  

    #irb  
    Also known as: #irb
  

  

    This method is for internal use only.
  



  

    

Alias for irb.


  



  [ GitHub ]


  

  


# File 'prelude.rb', line 18



def irb
  require 'irb'
  irb
end


  








  

    #local_variable_defined?(symbol)  ⇒ Object   



  

    

Returns 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 the short version of the following code:



binding.eval("defined?(#{symbol}) == 'local-variable'")


  



  [ GitHub ]


  

  


# File 'proc.c', line 617



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

    if (!lid) return Qfalse;

    GetBindingPtr(bindval, bind);
    env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
    return get_local_variable_ptr(&env, lid) ? Qtrue : Qfalse;
}


  








  

    #local_variable_get(symbol)  ⇒ Object   



  

    

Returns the value of the local variable symbol.



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



This method is the short version of the following code:



binding.eval("#{symbol}")


  



  [ GitHub ]


  

  


# File 'proc.c', line 529



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;
    const rb_env_t *env;

    if (!lid) goto undefined;

    GetBindingPtr(bindval, bind);

    env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
    if ((ptr = get_local_variable_ptr(&env, lid)) == NULL) {
	sym = ID2SYM(lid);
      undefined:
	rb_name_err_raise("local variable `%1$s' is not defined for %2$s",
			  bindval, sym);
    }

    return *ptr;
}


  








  

    #local_variable_set(symbol, obj)  ⇒ Object   



  

    

Set local variable named symbol as obj.



def foo
  a = 1
  bind = binding
  bind.local_variable_set(:a, 2) # set existing local variable `a'
  bind.local_variable_set(:b, 3) # create new local variable `b'
                                 # `b' exists only in binding

  p bind.local_variable_get(:a)  #=> 2
  p bind.local_variable_get(:b)  #=> 3
  p a                            #=> 2
  p b                            #=> NameError
end



This method behaves similarly to the following code:



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



if obj can be dumped in Ruby code.


  



  [ GitHub ]


  

  


# File 'proc.c', line 577



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

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

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

    RB_OBJ_WRITE(env, ptr, val);

    return val;
}


  








  

    #local_variables  ⇒ Array   



  

    

Returns the names of the binding’s local variables as symbols.



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



This method is the short version of the following code:



binding.eval("local_variables")


  



  [ GitHub ]


  

  


# File 'proc.c', line 501



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

    GetBindingPtr(bindval, bind);
    env = VM_ENV_ENVVAL_PTR(vm_block_ep(&bind->block));
    return rb_vm_env_local_variables(env);
}


  








  

    #receiver  ⇒ Object   



  

    

Returns the bound receiver of the binding object.


  



  [ GitHub ]


  

  


# File 'proc.c', line 637



static VALUE
bind_receiver(VALUE bindval)
{
    const rb_binding_t *bind;
    GetBindingPtr(bindval, bind);
    return vm_block_self(&bind->block);
}


  








  

    #source_location  ⇒ Array, Integer   



  

    

Returns the Ruby source filename and line number of the binding object.


  



  [ GitHub ]


  

  


# File 'proc.c', line 651



static VALUE
bind_location(VALUE bindval)
{
    VALUE loc[2];
    const rb_binding_t *bind;
    GetBindingPtr(bindval, bind);
    loc[0] = pathobj_path(bind->pathobj);
    loc[1] = INT2FIX(bind->first_lineno);

    return rb_ary_new4(2, loc);
}