ruby

The order is as follows: required arguments arguments with default values (arg=default_value notation) optional arguments (*args notation, sometimes called “splat parameter”) required arguments, again keyword arguments optional (arg:default_value notation, since 2.0.0) intermixed with required (arg: notation, since 2.1.0) arbitrary keyword arguments (**args notation, since 2.0.0) block argument (&blk notation) For example: def test(a, b=0, *c, … Read more

In Ruby 2.1 and later, you can use Binding#local_variable_get. In prior versions of Ruby, you have to use eval. If you want to do some sanity-checking before evaluating a supposed variable name, you can check whether the named variable is in local_variables.

Object#send >> a = “class” >> “foo”.send(a) => String >> a = “reverse” >> “foo”.send(a) => “oof” >> a = “something” >> “foo”.send(a) NoMethodError: undefined method `something’ for “foo”:String

It’s a matter of scope. A local variable is only visible/usable in the method in which it is defined (i.e., it goes away when the method returns). An instance variable, on the other hand, is visible anywhere else in the instance of the class in which it has been defined (this is different from a … Read more