What is the difference between include and extend in rails?

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 include and require in Ruby?

Use the include Method in Ruby

Unlike require , which loads an entire file's code, include takes a module name and makes all its methods available to other classes or modules.

How do you use extend in Ruby?

Extend is also used to importing module code but extends import them as class methods. Ruby will throw an error when we try to access methods of import module with the instance of the class because the module gets import to the superclass just as the instance of the extended module.

What is the difference between load and require?

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.

Can I include a class in Ruby?

include is the most used and the simplest way of importing module code. When calling it in a class definition, Ruby will insert the module into the ancestors chain of the class, just after its superclass.

Ruby modules - Extend and Include

What is :: in Ruby?

The :: is a unary operator and is used to access (anywhere outside the class or module) constants, instance methods and class methods defined within a class or module. Note: In Ruby, classes and methods may be considered constants too.

What is proc and 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. def proc_demo_method. proc_demo = Proc. new { return "Only I print!" }

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 I add a module in Rails?

You can include a module in a class in your Rails project by using the include keyword followed by the name of your module. Now you should be able to do Customer. new. hello and get “hello” as a result.

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 the difference between include and extend in UML?

The include relationship supports the reuse of functionality in a use-case model. 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 Singleton 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.

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 .

What is include in Rails?

Rails provides an ActiveRecord method called :includes which loads associated records in advance and limits the number of SQL queries made to the database. This technique is known as "eager loading" and in many cases will improve performance by a significant amount.

What is %W in Ruby?

%w(foo bar) is a shortcut for ["foo", "bar"] . Meaning it's a notation to write an array of strings separated by spaces instead of commas and without quotes around them. You can find a list of ways of writing literals in zenspider's quickref.

How does include work in Ruby?

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 is module in ROR?

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 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 difference between module and class in Rails?

Modules are about providing methods that you can use across multiple classes - think about them as "libraries" (as you would see in a Rails app). Classes are about objects; modules are about functions. For example, authentication and authorization systems are good examples of modules.

What is difference between class variable and instance variable?

Class variables also known as static variables are declared with the static keyword in a class, but outside a method, constructor or a block. Instance variables are created when an object is created with the use of the keyword 'new' and destroyed when the object is destroyed.

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

A class is more of a unit, and a module is essentially a loose collection of stuff like functions, variables, or even classes. In a public module, classes in the project have access to the functions and variables of the module. You don't have to specify the module name to address one.

What is the difference between block proc and lambda?

When using parameters prefixed with ampersands, passing a block to a method results in a proc in the method's context. Procs behave like blocks, but they can be stored in a variable. Lambdas are procs that behave like methods, meaning they enforce arity and return as methods instead of in their parent scope.

What is &Block in Ruby?

The &block is a way of sending a piece of Ruby code in to a method and then evaluating that code in the scope of that method. In your example code above it means a partial named cart will be rendered in a div.

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.