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Debugging in Rails

What is debug in Rails?

Rails debugging presents an essential technique necessary to uncover the root cause of issues in Ruby on Rails applications. Tests may miss certain faults, and it becomes the role of debugging to ensure such slipped problems are addressed.

Benefit of Debugging

Debugging grants developers the ability to inspect the contents of a variable. Using debug helpers, Rails can represent valuable readable data from any object or variable.

Debug Helpers

A common debug helper, the debug helper, for instance, is used to return a tag to render objects into the human-readable YAML format. For example, @article @article title will give an output resembling: Article body.

Object Conversion to YAML

Using to_yaml on any object will convert it to YAML. In simpler terms, it’s like translating a text from German to English, granting the developer a reading-friendly representation.


Another vital aspect is logging, which works by printing messages into a corresponding log file at the Rails.root/log/. The log file’s name corresponds to the environment where the application is running.

Logging Utility

The ingenuity of logging in rails is portrayed through the freedom developers can write into the current log from within a controller.

Log Levels

Rails allows the configuration of log levels, where a message is only printed into the log if its log level is at par or higher than the configured log level.

Impact on Performance

The debug level will inevitably impact performance more than other levels such as fatal because Ruby has to evaluate strings, involving variables’ interpolation. However, you can mitigate this impact by evaluating the contents of the block only when debug is enabled, thus reducing the performance hit.

Verbose Query Logs

In Rails, verbose query logs aim to enhance debugging performance by printing source locations of methods that enqueue background jobs. They are enabled by default in the development environment, but it’s not advised to use them in a production environment.

Tagged Logging

TaggedLogging in Rails aids in debugging by tagging log lines with subdomains, and request ids, among other aspects.

Debugger Usage

The debugger is an invaluable tool in Rails, as it provides pivotal insights into the Ruby source code and the code you’ve written.

Navigating Stack Frames

The backtrace command lists the frames on the stack. Using it is like taking a metaphorical introspective journey down our application’s stack to understand the sequence of function calls made.

Breakpoint Insertion

Breakpoints are like a pit stop in a Formula 1 race, allowing us to stop the execution flow at specific points. You can add breakpoints directly into your code or use commands to insert them during runtime.


The console is a significant tool in Rails Debugging. Essentially, the console is an arena where you can author and test your ideas in Ruby code, create new classes, instantiate models, inspect variables, and much more.

Wrap Up

In a nutshell, rails debugging is an instrumental topic in web development. It empowers developers with techniques like logging, breakpoints, consoles, etc., to uncover hidden issues, and ensure application reliability. This tutorial equipped you with the fundamental techniques and a deep dive into the nitty-gritty of debugging in Rails.

To understand more about Ruby on Rails and related topics, consider checking out the previous article about Rails Mailers, which details sending emails from your Rails application.

Check out another informative article about Rails, which we’ll soon feature on our site. Stay tuned!


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