The Life‑Changing Magic of Ruby and Rails

Autoloading Modules in Rails

Autoloading modules allows you to speed up the initialization of your library by lazily loading the code you need. This post explores how autoload method works.

Autoloading Modules in Rails
Autoloading Modules in Rails

Typically, you use require to load libraries or files that your code needs. Ruby also provides an autoload method that lazily loads the specified modules. The Rails framework overrides and abundantly uses this method.

What does the `autoload` method do, and how does it work?

Autoloading in Ruby

Let's try to understand Ruby's autoload method first.

autoload in Ruby
autoload in Ruby

This method takes two arguments: module (string/symbol) and filename (string), and registers the filename to be loaded the first time that module is accessed.

Using autoload allows you to speed up the initialization of your library by lazily loading the modules that your code depends on. It won't load the library or framework code you don't need.

Autoloading in Rails

Ruby on Rails provides its own `autoload` method via its Active Support framework.

It allows you to define autoload based on Rails naming conventions. It automatically guesses the filename based on the module name.

autoload in Rails
autoload in Rails

Here's the simplified implementation of this method in Rails.

simplified implementation
simplified implementation

If the path is not provided, Rails guesses the path by joining the constant name with the current module name and generating its underscored and lowercase form. Finally, it calls Ruby's autoload method by calling super and passes the module name and the generated path.

Note: The lazy-loading nature of the autoload method sounds nice, but there's a caveat to keep in mind. Many modules in Ruby and especially Rails, monkey-patch (modify) other classes. That means how your code works may depend on whether a module has been used yet.

So this concludes our exploration of how autoloading works in Rails. I hope you learned something new. I sure did. Let me know if you liked this post or have any feedback. I look forward to hearing from you.

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