mruby-mruby/mrbgems/mruby-metaprog

mruby-metaprog

This mrbgem provides a collection of methods for metaprogramming in mruby. Metaprogramming is the ability of a program to inspect, modify, and create its own code at runtime.

Functionality

The mruby-metaprog mrbgem offers methods for:

• Instance Variable Manipulation:
  • instance_variable_defined?(symbol): Checks if an instance variable is defined in an object.
  • instance_variable_get(symbol): Retrieves the value of an instance variable.
  • instance_variable_set(symbol, value): Sets the value of an instance variable.
  • instance_variables(): Returns an array of instance variable names in an object.
• Method Inspection:
  • methods(regular=true): Returns a list of public and protected methods of an object.
  • private_methods(all=true): Returns a list of private methods accessible to an object.
  • protected_methods(all=true): Returns a list of protected methods accessible to an object.
  • public_methods(all=true): Returns a list of public methods accessible to an object.
  • singleton_methods(all=true): Returns an array of singleton method names for an object.
• Singleton Method Definition:
  • define_singleton_method(name, &block): Defines a singleton method for an object.
• Class Variable Manipulation:
  • class_variable_defined?(symbol): Checks if a class variable is defined in a module.
  • class_variable_get(symbol): Retrieves the value of a class variable.
  • class_variable_set(symbol, value): Sets the value of a class variable.
  • class_variables(inherit=true): Returns an array of class variable names in a module.
  • remove_class_variable(symbol): Removes a class variable from a module.
• Module Inspection:
  • included_modules(): Returns a list of modules included in a module or class.
  • instance_methods(include_super=true): Returns an array of public and protected instance methods in a module or class.
  • public_instance_methods(include_super=true): Returns an array of public instance methods in a module or class.
  • private_instance_methods(include_super=true): Returns an array of private instance methods in a module or class.
  • protected_instance_methods(include_super=true): Returns an array of protected instance methods in a module or class.
  • undefined_instance_methods(): Returns an array of undefined instance methods in a module/class.
• Method Removal:
  • remove_method(symbol): Removes a method from a class.
• Constant Inspection:
  • constants(inherit=true): Returns an array of constant names defined in a module.
• Module Nesting:
  • Module.nesting(): Returns an array representing the current module nesting.
• Message Sending:
  • send(symbol, *args, &block): Invokes a method on an object.
  • public_send(symbol, *args, &block): Invokes a public method on an object.
• Variable Inspection:
  • global_variables(): Returns an array of global variable names.
  • local_variables(): Returns an array of local variable names in the current scope.

Examples

Working with Instance Variables

class MyClass
  def initialize(value)
    @my_var = value
  end
end

obj = MyClass.new(10)

p obj.instance_variable_defined?(:@my_var)  #=> true
p obj.instance_variable_get(:@my_var)     #=> 10
obj.instance_variable_set(:@another_var, "hello")
p obj.instance_variables                   #=> [:@my_var, :@another_var]

Inspecting Methods

class AnotherClass
  def public_method; end
  protected
  def protected_method; end
  private
  def private_method; end
end

obj = AnotherClass.new
p obj.public_methods(false)    #=> [:public_method]
p obj.protected_methods(false) #=> [:protected_method]
p obj.private_methods(false)   #=> [:private_method]

def obj.singleton_method_example; end
p obj.singleton_methods        #=> [:singleton_method_example]

Defining Singleton Methods

obj = Object.new
obj.define_singleton_method(:greet) do |name|
  "Hello, #{name}!"
end
p obj.greet("World")  #=> "Hello, World!"

Working with Class Variables

class ParentClass
  @@parent_cvar = 100
end

class ChildClass < ParentClass
  @@child_cvar = 200

  def self.get_parent_cvar
    class_variable_get(:@@parent_cvar)
  end
end

p ChildClass.class_variable_defined?(:@@child_cvar)  #=> true
p ChildClass.class_variable_get(:@@child_cvar)     #=> 200
ChildClass.class_variable_set(:@@new_cvar, 300)
p ChildClass.class_variables.sort                   #=> [:@@child_cvar, :@@new_cvar, :@@parent_cvar] (order may vary)
p ChildClass.get_parent_cvar                        #=> 100
ChildClass.remove_class_variable(:@@new_cvar)
p ChildClass.class_variables.sort                   #=> [:@@child_cvar, :@@parent_cvar] (order may vary)

License

This mrbgem is licensed under the MIT License.