Rails Console
`rails c` with me - turbocharge your use of the interactive console
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`rails c` with me - turbocharge your use of the interactive console

Sweta Sanghavi • May 17, 2022 • Portland, OR

In this video titled rails c with Meturbocharge your use of the interactive console, Sweta Sanghavi presents valuable insights on maximizing the Rails console as a powerful tool for developers. The session aims to deepen understanding of the console’s features, providing tactics for efficient debugging and development.

The key points discussed are as follows:
- Introduction to Rails Console: Sweta explains rails c as a command for interacting with a Rails application via the command line, enabling access to the underlying data without a web UI.
- Utilizing Console Features: The console allows evaluation of Ruby code in specific contexts, minimal setup requirements, and quick error feedback, making it an effective exploratory tool for developers.
- Understanding IRB and Subsessions: The Rails console is built on the Interactive Ruby Shell (IRB), which supports subsessions for context management. Developers can define variables and methods and navigate between subsessions to evaluate their code while checking the scope and context.
- The Role of Binding: Sweta explains the concept of binding in Ruby, which encapsulates the execution context, allowing more granular control over method evaluation.
- Parsing Ruby and Syntax Trees: Ripper, a Ruby library, is introduced as a tool to view abstract syntax trees of code, illustrating how Ruby processes command parsing for better understanding of code behavior.
- Console Interactivity: The video highlights features such as syntax highlighting and inline editing similar to text editors, facilitated by the reline library, that improve usability.
- Performance Debugging: Techniques like leveraging the Benchmark library and the explain method for Active Record queries are suggested for honing in on performance issues in live applications.
- Using Console in Production: Caution is advised when running console commands in production, with recommendations to use sandbox mode for safety, allowing experimentation without affecting live data.
- Fast Experimentation and Data Queries: The console is a valuable resource for quick data evaluations, which can assist developers in informed product decisions and measuring feature adoption.

In conclusion, this session emphasizes the potential of the Rails console in enhancing productivity and debugging skills for developers. Key takeaways include: maximize the usage of Rails console for debugging, take advantage of its features for performance optimization, and utilize it effectively in both development and production environments. Sweta encourages attendees to experiment with the console to gain confidence and mastery in their Rails applications.

`rails c` with me - turbocharge your use of the interactive console
Sweta Sanghavi • May 17, 2022 • Portland, OR

Spinning up the rails console can be a quick way to answer a question with a back of the envelope calculation. But, what else can we use it for, and how does it work? Allow me to show you new ways to leverage the console's features and become an even more expert debugger. You'll leave with some simple tactics to save you time and write more performant code. While you're here, we'll look under the hood to see how the features of the console are encoded and we'll trace back the history of these libraries to see how they arrived in our Rails application.

RailsConf 2022

00:00:00.900 Welcome to Rails C! Today, we're going to learn how to turbocharge our use of the interactive console.
00:00:12.420 Good morning, everyone! I'm excited to be here with all of you.
00:00:15.960 Thank you for the warm welcome. My name is Sweta Sanghavi, and I'm a senior developer at BackerKit.
00:00:21.840 At BackerKit, we build software that helps crowdfunding creators to build community and fulfill their projects. If you've backed a project, you might have received a survey from us.
00:00:32.940 I began my journey with Rails after a previous career as a life science consultant. In my early stages of learning Rails, I came to really love the console. My goal today is to inspire you to appreciate this tool that we all have at our fingertips.
00:00:50.280 The console provided an easy way for me to get to know the Rails environment and deepen my understanding of Ruby. Today, we'll start by taking a deep dive into the console and checking under the hood to see what enables us to use the features that we depend on.
00:01:02.100 We will explore how to store context, evaluate Ruby, and engage with the interactivity we've come to expect. Then, we'll discuss tactics to supercharge your usage of this tool to become an even more effective developer.
00:01:14.220 So, what is Rails console? The console command gives us a way to interact with our Rails application from the command line. It provides access to the data underneath our application, allowing us to make changes without loading the web UI.
00:01:30.120 With the console, we can use gems and libraries to facilitate data retrieval, such as Active Record. This way, we can run queries and understand the state of users or other objects in our application.
00:01:50.040 We're even able to define and execute Ruby code right in the console. The console allows us to evaluate a piece of code in a specific context, enabling us to focus on a method or class we want to learn more about.
00:02:06.480 It requires very little setup; you can use it right out of the box. Moreover, the context is configurable—you can define classes, methods, variables, and other elements to aid your exploration of the application.
00:02:19.440 The console provides quick feedback about Rails functionality, allowing us to see human-readable errors when something goes wrong. Today, our goal is to use the console to learn more about its capabilities.
00:02:36.600 How is it able to do all these great things? Rails console actually uses the Interactive Ruby Shell (IRB) behind the scenes. When I first started learning Ruby, I used the IRB console to interact with Ruby code.
00:02:51.180 Similarly, our console utilizes IRB, which provides access to all the core Ruby libraries. It's fast and useful for interactions that primarily involve Ruby.
00:03:11.640 Additionally, you have the option to import other Ruby libraries into your IRB session by installing a gem and requiring it, or simply requiring any other Ruby libraries you've defined.
00:03:30.360 However, you may not always want to install every gem included in your Rails application, or keep track of versioning. That's where Bundler comes in. You can call 'bundle console' to spin up a console that has access to both the core Ruby libraries and the gem code at the versions specified in your Gemfile.
00:03:54.020 When you want access to your entire Rails application, you can spin up the Rails console, providing access to a complete Rails environment, including auto-loading and initialization of the application—all the features you expect.
00:04:17.680 Let's discuss some of the features that make the console so effective, starting with storing context. If you call a method or variable that the console doesn't recognize, it will typically raise an error, such as an undefined local variable or method error. However, we can actually store context within our session.
00:04:30.780 By defining a method, such as 'full_name', we can access that method when we call it. The IRB uses sub-sessions to save and differentiate context effectively.
00:04:50.400 When you spin up a console, you start in a sub-session in the context of an object called 'main.irb'. This context is indicated by 'main' in parentheses. Anything executed in this console runs in that main context.
00:05:02.460 Let's play with how sub-sessions work to gain a better understanding of storing context. By using the command 'IRB', we can start a new sub-session. You may notice a number indicating that you're now in a new sub-session.
00:05:19.920 Using the 'jobs' command, you can output the sub-sessions in your current IRB session, showing both the original session and the new sub-session.
00:05:38.820 Let's check what's shared and not shared between these two sub-sessions. By switching back to the initial sub-session and setting a variable, 'display_name', we can check its value in the new sub-session.
00:05:53.760 When we try to call 'display_name' in the new session, we find that we no longer have access to that variable. Interestingly, however, we can still call the method 'full_name' that we defined in the original session.
00:06:09.780 So, how is this possible? Another important aspect to consider is the concept of a workspace, which keeps track of sub-sessions. Each sub-session maintains its context, while workspaces represent the top level containing those sub-sessions.
00:06:30.660 The context keeps track of the execution state at any given point within our program. This leads us to an important topic: instance variables, instance methods, and the concept of 'self'.
00:06:44.280 Together, these contribute to what we refer to as the execution context. In Ruby, access to context is facilitated through the Binding object. This built-in Ruby class can encapsulate the context at your current scope.
00:06:57.380 The Binding object can be passed around as an argument, allowing us to evaluate code in a specific context.
00:07:06.779 Next, let's explore the console's ability to parse Ruby code. Through our earlier example of 'full_name', we see that we're able to evaluate Ruby code within the console.
00:07:18.660 The console needs to parse and evaluate this code, but how does that happen? I want to take a moment to discuss Abstract Syntax Trees (ASTs). An AST is a low-level representation of a program's structure.
00:07:31.020 A parser can transform Ruby code into an AST, allowing for easier compilation and translation between languages. In Ruby, we have a library called Ripper that provides insight into how Ruby handles parsing.
00:07:48.779 Ripper can output the tree that Ruby uses to parse the code, giving us an interface to explore its inner workings.
00:08:02.400 Using Ripper, we can request different types of trees, and since we have access to core Ruby in our console, we can explore various nodes and their structures.
00:08:17.460 For instance, we can use the 's(:method_name)' method to output a symbolic expression tree. Let's evaluate the output for a method definition, such as 'full_name'.
00:08:32.160 When we call this method with our method definition, we see a structured representation of our code—a symbolic expression organized in an array format.
00:08:49.559 Step by step, we can analyze the components. Initially, we observe the symbol 'program' alongside the keyword 'def', signifying the start of a new method definition.
00:09:05.640 Next, we introduce the variable 'ident', which refers to the identifier for our method 'full_name'. Following this, we see parameter representation, defining 'first_name' and 'last_name'.
00:09:21.660 Lastly, we reach the body of the method, as indicated by the body statement. Within this segment, we can identify local variables represented by 'VAR ref' of 'first_name' and 'last_name'.
00:09:39.180 Although not every element of Ripper's output may be immediately clear, it serves as a valuable tool for understanding how Ruby parses and processes code.
00:09:55.740 You can experiment with Ripper in your own console as well. I encourage you to evaluate some code and take a look!
00:10:08.580 Another feature worth discussing is the interactivity of the console, made possible by the readline GitHub integration.
00:10:20.280 We are all accustomed to using the console in a text-editor-like format, benefiting from features like indenting and syntax highlighting.
00:10:34.200 Hit Ctrl+A or Ctrl+E to navigate through a line. Many of these commands come from a source library named 'newreadline', which provides inline editing and history capabilities.
00:10:50.879 Originally released in 1989, this library allows for improved interaction with various shells. In Ruby, there's a line editor called Readline that further extends this functionality.
00:11:01.920 This Ruby Readline provides features like auto-completion and history access when entering commands, facilitating a better console experience.
00:11:12.300 Since then, some of the limitations of the Readline library prompted the creation of 'reline', a pure Ruby implementation that supports multi-line editing commands.
00:11:24.660 This change sparked a fascinating evolution of software libraries and tools as we've integrated them into our day-to-day development work.
00:11:37.440 Are we ready to turbocharge our use of the console? In this section, I'll share how to use the console to enhance your development skills and efficiency.
00:11:51.960 We can leverage console features for performance improvements, debugging, and enhancing our day-to-day product development.
00:12:06.660 First, let's discuss performance. Tools like New Relic can provide transaction traces for pages that take too long to load. However, after receiving this feedback, additional debugging is often necessary to identify the changes needed to improve load time.
00:12:24.360 The console excels in helping you pinpoint performance issues in your code. ActiveRecord and scopes may abstract complexity, making it harder to see performance culprits like inefficient queries.
00:12:45.960 Using the Benchmark library in the console can help you measure the execution time of specific methods. The measure method from Benchmark outputs how long it took to execute your code in seconds.
00:13:03.600 Once you isolate a problematic segment of code, try commenting it out to observe whether your page load times improve as expected.
00:13:23.280 You can also run 'to_sql' on any ActiveRecord query to reveal the underlying SQL code. This allows a quick check to ensure your query is performing as intended.
00:13:39.759 Additionally, the 'explain' method can be invaluable for performance debugging. When executed on an ActiveRecord query, it triggers the query and outputs a query plan, detailing the method's execution.
00:13:58.920 The structure of the query plan reveals necessary scans, which can help decide if adding an index could improve performance.
00:14:18.720 In some cases, closely mimicking production behavior may require accessing the production console. This unique interface allows you to gather precise data and context to understand performance in users' environments.
00:14:38.880 When using the production console, exercise caution, as changes made here will affect live production data. However, it provides an opportunity to run benchmarks or troubleshoot issues directly.
00:14:56.100 To mitigate mistakes, consider using 'sandbox mode', which rolls back any changes made during the session. This provides a safety net for testing without risk.
00:15:09.479 When speeding through a console session, you can clear the console with 'Command K' to focus on specific actions without scrolling through old logs.
00:15:28.920 Additionally, remember that console sessions don't automatically reload code changes from your application. Use the 'reload' command to refresh your context before testing.
00:15:47.640 If you've ever lost track of variables, the underscore (_) variable captures the last result of an expression. Utilizing this can save time by allowing quick access to previously executed expressions.
00:16:03.720 For quick command retrieval, use Ctrl + R, which initiates reverse command search. Typing in a previously run command lets you rerun it without retyping the entire command.
00:16:18.960 I compiled a cheat sheet of useful commands for quicker reference that may assist you during your development process.
00:16:36.600 Lastly, I would like to express gratitude to BackerKit for their support in my journey to speak at conferences, and at the same time, an acknowledgment to wnbrb for their role in fostering a strong community for women and non-binary Rubyists.
00:17:09.960 Thank you everyone for attending today's session on turbocharging your Rails console usage. If there's anything from this talk that resonates with you, or if you try implementing something you've learned today, please let me know. I'd love to hear your feedback!
00:17:31.260 Here's my email and my handle.
00:17:33.360 I hope you have a fantastic day!
SS
Sweta Sanghavi
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