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 are controller callbacks in rails?

Rails provides before and after actions in controllers as an easy way to call methods before or after executing controller actions as response to route requests.

What are Active Record callbacks?

Active Record Callbacks are hooks to which we can register methods in our models. These hooks are executed in various stages of an Active Record object lifecycle. The following callbacks are run when an object is created. These callbacks are executed in the order in which they are listed below.

What are Ruby callbacks?

Technically, a “callback” is just executable code that is passed as an argument to a function. Ruby describes their callbacks as hooks into object life cycles, where a “hook” is a way to execute code before, after, or instead of existing code.

What is the difference between delete and destroy in rails?

Basically destroy runs any callbacks on the model while delete doesn't. Deletes the record in the database and freezes this instance to reflect that no changes should be made (since they can't be persisted). Returns the frozen instance.

ActiveRecord Callbacks in Rails

What is dependent destroy in rails?

dependent: :destroy

Rails, when attempting to destroy an instance of the Parent, will also iteratively go through each child of the parent calling destroy on the child.

What is delegate in Ruby on Rails?

delegate provides a delegate class method to easily expose contained objects' public methods as your own. Simply say, through delegation you can use public methods in other model directly. For example I have a QueueItem and a Video model.

What is a lambda in Ruby?

In Ruby, a lambda is an object similar to a proc. Unlike a proc, a lambda requires a specific number of arguments passed to it, and it return s to its calling method rather than returning immediately.

What is Active Record in Ruby?

Active Record is the M in MVC - the model - which is the layer of the system responsible for representing business data and logic. Active Record facilitates the creation and use of business objects whose data requires persistent storage to a database.

What is hook in Ruby?

Ruby Hook Methods are called in reaction to something you do. They are usually used to extend the working of methods at run time. These methods are not defined by default, but a programmer can define them according to imply them on any object or class or module and they will come into picture when certain events occur.

What are scopes in Rails?

Scopes are custom queries that you define inside your Rails models with the scope method. Every scope takes two arguments: A name, which you use to call this scope in your code. A lambda, which implements the query.

What are filters in rails?

Rails filters are methods that run before or after a controller's action method is executed. They are helpful when you want to ensure that a given block of code runs with whatever action method is called.

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 does render JSON do in Rails?

By using render json: , we are converting all the model instances into JSON. to_json method can add tacked on, but it is optional, as it will be called implicitly, thanks to Rails doing work behind the scenes.

What is before action in Rails?

before_filter/before_action: means anything to be executed before any action executes. Both are same. they are just alias for each other as their behavior is same.

What are strong parameters in Rails?

Strong Parameters, aka Strong Params, are used in many Rails applications to increase the security of data sent through forms. Strong Params allow developers to specify in the controller which parameters are accepted and used.

What is Monkey Patch 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 Active Record and ORM in Rails?

Rails Active Record is the Object/Relational Mapping (ORM) layer supplied with Rails. It closely follows the standard ORM model, which is as follows − tables map to classes, rows map to objects and. columns map to object attributes.

Is Active Record an ORM?

ActiveRecord is an ORM. It's a layer of Ruby code that runs between your database and your logic code.

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 yield in 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 are procs in Ruby?

A Proc object is an encapsulation of a block of code, which can be stored in a local variable, passed to a method or another Proc, and can be called. Proc is an essential concept in Ruby and a core of its functional programming features.

What is alias in Ruby?

To alias a method or variable name in Ruby is to create a second name for the method or variable. Aliasing can be used either to provide more expressive options to the programmer using the class or to help override methods and change the behavior of the class or object.

What is polymorphic association in Rails?

In Ruby on Rails, a polymorphic association is an Active Record association that can connect a model to multiple other models. For example, we can use a single association to connect the Review model with the Event and Restaurant models, allowing us to connect a review with either an event or a restaurant.

What is method missing in Ruby?

method_missing is a method that ruby gives you access inside of your objects a way to handle situations when you call a method that doesn't exist. It's sort of like a Begin/Rescue, but for method calls. It gives you one last chance to deal with that method call before an exception is raised.