Ruby “Require” Method

What is the "require" Method in Ruby?

The "require" method in the Ruby programming language is used to import external files or libraries, typically referred to as "gems" or "modules," into a Ruby program. These documents or libraries may include extra classes, modules, or methods that enhance the functionality of the program.

Consider a real-world scenario where a Ruby developer is working on a web application that requires functionality for handling and processing images. Instead of reinventing the wheel and writing complex image manipulation algorithms, the developer can make use of a well-established gem like "RMagick" by utilizing the "require" method. By simply including the necessary library, the developer gains access to a range of image-related functionalities, such as resizing, cropping, and applying filters. This not only accelerates the development process but also ensures the utilization of tested and optimized code for handling image-related tasks.

Ruby also has the "require_relative" method in addition to the "require" method. It allows us to load files relative to the directory of the currently open file rather than searching the load path. When working with project-specific files or modules that are not part of a globally installed library or gem, this is very helpful.

Syntax of Ruby Require

The ruby "require" method has a simple syntax. The following syntax is used to load a file or library from an external source:

Here, 'file_name' stands for the name of the file or library that has to be loaded. Ruby often ignores the file extension since it knows it's a Ruby file (.rb) or a platform-specific shared library (.so,.dll, etc.).

How does a Required Statement Work in Ruby?

When the "require" method is used, Ruby looks for the specified file or library in its predefined search path, which includes the current directory and other locations specified by the $LOAD_PATH variable. If the file is located, the program loads it. If a required file or library cannot be found, Ruby generates a "LoadError" message.

It's important to keep in mind that the "require" method only loads the file once. The repetitive use of multiple "require" statements for the same file results in future calls being ignored.

How to Implement "require" in Ruby?

Suppose we have a file called "math_operations.rb" that includes some functions. We want to use the functions given in this file in another Ruby file. To do this, we may use the "require" approach as follows:

We create a file called "math_func.rb" and define some functions.

We then use the "require" function in another Ruby file to import the "math_func.rb" file and use the methods specified within it.

Explanation

In this case, the file was loaded using the relative file path ./math_func.rb. The file is in the current directory according to the ./ prefix in ./math_func.rb. We must specify the correct file path if the file is located in a different directory.

Ruby Require vs. Include

The ruby require method is similar to the include method seen in other programming languages. It enables us to load and run another file within our Ruby program.

The include method in Ruby has a different purpose. It enables the inclusion of methods from one module into another module or class. Unlike file-level operations, this feature works at the class level. When a module is included, its methods become accessible within the current module or class, extending its functionality. This concept is called a mix-in because it allows us to incorporate reusable code from other modules into our classes. For example, by including the "Enumerable" module and using its "each" function, a class can exhibit collection-like behavior.

Differences between "require" and "load"

Explanation of the "load" Method

The load method in Ruby bears resemblances to the require method, although there are notable differences. When using the load method, it loads and executes the specified file. Unlike require, the load method does not maintain a record of whether the file has been previously loaded. Here is the syntax for the load method:

Here, 'file_name' represents the name of the file to be loaded.

Differences in Behavior between "require" and "load"

To understand the differences in behavior between require and load, consider the following example:

We have a file named "base.rb":

We now create another file to implement the load method:

Output

Explanation

Since this file calls the load twice, the print statement of the "base.rb" also gets executed twice

We now create another file to implement the require method:

Output

Explanation

The print statement is only used once in this case.

Thus, the load function loads the file twice, executing its content simultaneously. The "require" technique, on the other hand, loads the file only once and skips the second load.

When to Use "load" and When to Use "require"?

The decision between load and require is determined by the program's unique requirements:

• When we wish to load a file or library only once and avoid duplication, we use the "require" technique. It is typically used to load shared or external libraries.
• The load method is used when we want to load a file every time it is called. This is particularly useful in scenarios where the code needs to be dynamically loaded or when the file's content can vary between each loading.