What is ActiveSupport concern?

ActiveSupport's Concern module allows us to mix in callbacks, class and instance methods, and create associations on target objects. This module has an included method, which takes a block, as well as an append_features method and class_methods block, which you can read about in the source code.

What are Rails concerns?

A Rails Concern is a module that extends the ActiveSupport::Concern module. Concerns allow us to include modules with methods (both instance and class) and constants into a class so that the including class can use them. A concern provides two blocks: included.

What are Rails modules?

Modules provide a structure to collect Ruby classes, methods, and constants into a single, separately named and defined unit. This is useful so you can avoid clashes with existing classes, methods, and constants, and also so that you can add (mix in) the functionality of modules into your classes.

What is Mixins in Rails?

Mixins provides a controlled way of adding functionality to classes. The code in the mixin starts to interact with code in the class. In Ruby, a code wrapped up in a module is called mixins that a class can include or extend. A class consist many mixins.

What is prepend in Ruby?

With prepend, the module is added before the class in the ancestor chain. This means ruby will look at the module to see if an instance method is defined before checking if it is defined in the class. This is useful if you want to wrap some logic around your methods.

Ruby on Rails | Concerning in Rails

What is the difference between proc and lambda?

Procs return from the current method, while lambdas return from the lambda itself. Procs don't care about the correct number of arguments, while lambdas will raise an exception.

What is a singleton class in Ruby?

Singleton is a creational design pattern, which ensures that only one object of its kind exists and provides a single point of access to it for any other code. Singleton has almost the same pros and cons as global variables. Although they're super-handy, they break the modularity of your code.

Why we are using mixin in Rails?

Modules are one of the shiniest resources of Ruby because they provide two great benefits: we can create namespaces to prevent name clashes and we can use them as mixins to share code across the application. Similar to classes, with modules we also group methods and constants and share code.

What is a mixin programming?

Mixins are a language concept that allows a programmer to inject some code into a class. Mixin programming is a style of software development, in which units of functionality are created in a class and then mixed in with other classes. A mixin class acts as the parent class, containing the desired functionality.

What are callbacks in Rails?

In Rails, callbacks are hooks provided by Active Record that allow methods to run before or after a create, update, or destroy action occurs to an object. Since it can be hard to remember all of them and what they do, here is a quick reference for all current Rails 5 Active Record callbacks.

What does :: mean in Rails?

::Rails selects the Module in the first code snippet, which is on the top-level. ::Rails::Engine selects the Class Engine which is in the top-level Rails Module.

How do you call a module method?

As with class methods, you call a module method by preceding its name with the module's name and a period, and you reference a constant using the module name and two colons.

What is metaprogramming in Ruby?

Metaprogramming is a technique by which you can write code that writes code by itself dynamically at runtime. This means you can define methods and classes during runtime.

What does extend ActiveSupport :: concern do?

Using extend ActiveSupport::Concern tells Rails that we are creating a concern. The code within the included block will be executed wherever the module is included. This is best for including third party functionality. In this case, we will get an error if the before_action is written outside of the included block.

What is the difference between extend and include in Ruby?

In simple words, the difference between include and extend is that 'include' is for adding methods only to an instance of a class and 'extend' is for adding methods to the class but not to its instance.

What is the difference between a class and a module Ruby?

What is the difference between a class and a module? Modules are collections of methods and constants. They cannot generate instances. Classes may generate instances (objects), and have per-instance state (instance variables).

How do mixins work?

As defined in Wikipedia, a mixin is a class containing methods that can be used by other classes without a need to inherit from it. In other words, a mixin provides methods that implement a certain behavior, but we do not use it alone, we use it to add the behavior to other classes.

When should you use mixins?

Is mixins a composition?

What are Mixins? Mixins are a form of object composition, where component features get mixed into a composite object so that properties of each mixin become properties of the composite object.

What is yield Ruby?

yield is a keyword in Ruby which allow the developer to pass some argument to block from the yield, the number of the argument passed to the block has no limitations, the main advantage of using yield in Ruby, if we face any situation we wanted to our method perform different functions according to calling block, which ...

What is Module_function Ruby?

module_function(*args) private. Creates module functions for the named methods. These functions may be called with the module as a receiver, and also become available as instance methods to classes that mix in the module. Module functions are copies of the original, and so may be changed independently.

What is polymorphism in Ruby?

Polymorphism is an important concept in object-oriented programming. It allows us to implement many different implementations of the same method, helping with code reusability and avoiding redundancy. In Ruby, we can implement polymorphism using inheritance or duck typing.

What is monkey patching in Ruby?

In Ruby, a Monkey Patch (MP) is referred to as a dynamic modification to a class and by a dynamic modification to a class means to add new or overwrite existing methods at runtime. This ability is provided by ruby to give more flexibility to the coders.

What is Eigenclass in Ruby?

Finally, let's try to give a proper definition of the eigenclass in Ruby: The eigenclass is an unnamed instance of the class Class attached to an object and which instance methods are used as singleton methods of the defined object.

What does Attr_accessor mean in Ruby?

Nouman Abbasi. In Ruby, object methods are public by default, while data is private. To access and modify data, we use the attr_reader and attr_writer . attr_accessor is a shortcut method when you need both attr_reader and attr_writer .