Ruby is a powerful and versatile programming language that has gained popularity among developers for its elegant syntax and object-oriented approach. One of the key features that sets Ruby apart from other languages is its support for private module methods. In this article, we will explore what private module methods are and how they can be used in Ruby.
To understand private module methods, we first need to understand what modules are in Ruby. A module is a collection of methods, constants, and classes that can be used to add functionality to a class. Modules are similar to classes, but they cannot be instantiated like classes. Instead, they are used as a mixin, which means they can be included in classes to provide additional functionality.
Now, let's dive into private module methods. Private methods are methods that can only be accessed within the class where they are defined. They cannot be called from outside the class, even by an instance of that class. Similarly, private module methods are methods that can only be accessed within the module where they are defined. They cannot be called from outside the module, even by a class that includes that module.
Private module methods are useful when you want to hide certain methods from external access. This can be particularly useful when working with large codebases or collaborating with other developers. By making certain methods private, you can prevent them from being accidentally called or overridden by other code.
To define a private module method in Ruby, we use the `private` keyword followed by the method name. This will make the method private and inaccessible from outside the module. Let's take a look at an example:
```ruby
module MathFunctions
private
def square(x)
x * x
end
end
```
In the above code, we have defined a `square` method as a private method within the `MathFunctions` module. This means that the `square` method can only be accessed within the module and cannot be called from outside.
Now, let's see how we can use this private module method in a class.
```ruby
class Calculator
include MathFunctions
def calculate_square(x)
square(x)
end
end
calculator = Calculator.new
calculator.calculate_square(5) # => 25
calculator.square(5) # => NoMethodError: private method `square' called for #<Calculator:0x00007f8c5e8e4d60>
```
As we can see, we have included the `MathFunctions` module in the `Calculator` class. This allows us to use the private `square` method within the class. However, if we try to call the `square` method directly on an instance of the `Calculator` class, we will get an error as the method is private and cannot be accessed from outside the module.
Private module methods can also be useful when we want to provide a public interface for a module while keeping the implementation details hidden. Let's take a look at an example of this:
