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 does ActiveSupport :: concern do?

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 is the use of concerns in Rails?

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. The code inside the included block is evaluated in the context of the including class.

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 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.

ActiveSupport Concerns in Rails

What does extend self do?

extend self includes all the existing instance methods as module methods. This is equivalent to saying extend Rake . Also Rake is an object of class Module . This can be used to define self contained modules with private methods.

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 does Require_relative do in Ruby?

require_relative allows you to "load a file that is relative to the file containing the require_relative statement". With require , ./ indicates a path that is relative to your current working directory.

What is extend and include in use case diagram?

The include relationship supports the reuse of functionality in a use-case model. Extend relationships. In UML modeling, you can use an extend relationship to specify that one use case (extension) extends the behavior of another use case (base).

What is extend in use case diagram?

The extension use case consists of one or several behavior sequences (segments) that describe additional behavior that can incrementally augment the behavior of the base use case. Each segment can be inserted into the base use case at a different point, called an extension point.

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 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 single table inheritance in Rails?

Single-table inheritance (STI) is the practice of storing multiple types of values in the same table, where each record includes a field indicating its type, and the table includes a column for every field of all the types it stores.

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 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).

What are services in Rails?

A service object in Rails is a plain old Ruby object created for a specific business action. It usually contains code that doesn't fit in the model or view layer, e.g., actions via a third-party API like posting a tweet.

What is an extend relationship?

An extend-relationship is a relationship from an extension use case to a base use case, specifying how the behavior defined for the extension use case can be inserted into the behavior defined for the base use case. It is implicitly inserted in the sense that the extension is not shown in the base use case.

What is the difference between uses and extends?

"includes" and "uses" indicates the mandatory use case where as "extends" indicates the optional use case.

What is the extend relationship between two use cases provide an example?

An extending use case can have non-optional behavior as well. This mostly happens when your modeling complex behaviors. For example, in an accounting system, one use case might be “Add Account Ledger Entry”. This might have extending use cases “Add Tax Ledger Entry” and “Add Payment Ledger Entry”.

What is the purpose of load Auto_load and Require_relative in Ruby?

-Auto_load: this initiates the method that is in hat file and allows the interpreter to call the method. -require_relative: allows the loading to take place of the local folders and files.

What is Load_path?

$LOAD_PATH is an array of absolute paths i.e it stores the exact location of all the dependencies in the project. The require keyword searches for the dependencies in the array $LOAD_PATH and tries to load it for the file that has a dependency on certain library.

What is difference between load and require in Ruby?

rb file every time the load function is called. You should use load function mainly for the purpose of loading code from other files that are being dynamically changed so as to get updated code every time. Require reads the file from the file system, parses it, saves to the memory, and runs it in a given place.

What is difference between PROC and block?

Procs are objects, blocks are not

A proc (notice the lowercase p) is an instance of the Proc class. This lets us call methods on it and assign it to variables. Procs can also return themselves. In contrast, a block is just part of the syntax of a method call.

What is the difference between proc and lambda in rails?

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.

Does End block Ruby?

Ruby blocks are anonymous functions that can be passed into methods. Blocks are enclosed in a do-end statement or curly braces {}. do-end is usually used for blocks that span through multiple lines while {} is used for single line blocks. Blocks can have arguments which should be defined between two pipe | characters.