Reflection and discovery and more in Ruby & SonicPi 🔍🕵️‍♀️

[jonnyhotchkiss]

Finding things like __FILE__

__FILE__ is a special literal in Ruby that returns the name of the current source file as a string ¹. It is used to reference the current file name in the code being executed. For example, require File.dirname(__FILE__) + "/../../config/environment" is a common usage of __FILE__ ¹.

In Sonic Pi, __FILE__ is also a special literal that returns the name of the current source file as a string ². It can be used to reference the current file name in the code being executed, similar to its usage in Ruby.

To identify what class/module __FILE__ belongs to, you can use the class method on it. For example, __FILE__.class will return String ¹².

To find things by name or source location and declaration, you can use Ruby's built-in reflection capabilities. For example, you can use Module.constants to get an array of all defined constants in the current scope ¹. You can also use Module.nesting to get an array of modules nested at the point of call ¹. To find all methods that begin with "__" or are all uppercase, you can use Module.instance_methods(false).grep(/^__/) and Module.instance_methods(false).grep(/^[A-Z_]+$/) respectively ¹.

I hope this helps!

Source: Conversation with Bing, 27/09/2023
(1) What does FILE mean in Ruby? - Stack Overflow. https://stackoverflow.com/questions/[2](https://kevinjmurphy.com/posts/revisiting-calling-sonic-pi-from-ruby/)[2](https://kevinjmurphy.com/posts/revisiting-calling-sonic-pi-from-ruby/)4379/what-does-file-mean-in-ruby.
(2) Revisiting Calling Sonic Pi From Ruby - Kevin Murphy. https://kevinjmurphy.com/posts/revisiting-calling-sonic-pi-from-ruby/.
(3) sonic-pi/core.rb at dev · sonic-pi-net/sonic-pi · GitHub. https://github.com/sonic-pi-net/sonic-pi/blob/dev/app/server/ruby/core.rb.

[jonnyhotchkiss]

methods

class MyClass
  def my_method
    # ...
  end

  private # private region ℹ

  def my_private_method
    # ...
  end
end

puts MyClass.public_instance_methods(false) # [:my_method]

[jonnyhotchkiss]

variables

1.times do
  a = 1
  puts "local variables in the block: #{local_variables.join ", "}"
end

puts "no local variables outside the block" if local_variables.empty?

Outer scope variables included in local-variables
See also Kernel#local_variables, but note that a for loop does not create a new scope like a block does.
Isolate variables from outer scope using ; in block arguments - see calling methods

[jonnyhotchkiss]

Methods and Variables in Ruby are very similar!

a = 0 if false # does not assign to a

p local_variables # prints [:a]

p a # prints nil

force a method call by using empty argument parentheses or by using an explicit receiver like self

Instance Variables @

Instance variables are shared across all methods for the same object.

Class variables @@

shared between a class, its subclasses and its instances.

Global variables $

Ruby has some special globals that behave differently depending on context such as the regular expression match variables or that have a side-effect when assigned to. See the global variables documentation for details.

[jonnyhotchkiss]

CONSTANTS

Any identifier starting with an uppercase letter.

Class and module definitions (see Modules and Classes) also define constants, assigned to the class/module name:

class A
  # ...
end
# Roughly equivalent to:
A = Class.new do
  # ...
end

See also: Constants scoping section in “Modules and Classes” chapter.

[jonnyhotchkiss]

Assignment

In the following sections any place “variable” is used an assignment method, instance, class or global will also work:

def value=(value)
  p assigned: value
end

self.value, $global = 1, 2 # prints {:assigned=>1}

p $global # prints 2

TBC! ....