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https://twitter.com/2181819888/status/1841512354359726306

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Greg Navis

@gregnavis

Apr 28, 2023

💡 Rails tip: Rails 7 shipped with error handling infrastructure

It's a small module, but I find it extremely useful, especially when integrating with third-party APIs, as you usually want to gracefully inform the user the API is down, but still report that internally.

Ready?

At a high level:

- there are multiple subscribers registered with the error reporter
- each error is passed to each subscriber
- the reporter offers methods for detecting, reporting, and swallowing exceptions thrown by the app

Let's take a close look at those methods.

Rails.error.handle - runs the block, swallows and records any exceptions raised by it

If no exceptions are raised then the block value is returned.

If an exception is raised then nil is returned, unless a fallback is given, but more on that in a minute.

Let's talk about ...

Read 11 tweets

Greg Navis

@gregnavis

Apr 5, 2023

💡 Ruby meta-programming tip: it's trivial to add support for object literals to Ruby

Object literals are frequently found in JavaScript: these are objects defined on the spot, both state and methods, without a prior class definition.

Let's try to add them to Ruby! ⬇️

Let's start with a JavaScript example: an app object comprised of a database connection and a router; there's a method to start the whole thing up.

The app object was instantiated without a class definition.

How would a Ruby counterpart look like?

Theoretically, we could define a Hash mapping keys to objects, some of these objects being Procs.

This would be a direct translation of JavaScript code, but it wouldn't fit the Ruby object model and would feel extremely unidiomatic.

Fortunately, we can do better. MUCH better!

Read 7 tweets

Greg Navis

@gregnavis

Mar 25, 2023

💡 Ruby meta-programming: lazy accessors are simple to implement and more robust than lazy computations via ||=

Meta-programming can be fun, productive, and helpful. Let's have a look at another example, including a bigger engineering lesson.

⬇️ Let's go!

What's a lazy accessor?

It's an accessor with a block of code to determine a value. That block of code is called only on first use; subsequent calls reuse the value the block returned.

In short: lazy accessor = laziness + caching

What are its applications?

Primarily, deferring expensive computations until needed and ensuring they are run only once.

Example: expensive database reporting query with further result processing in Ruby.

Let's have a look at the idiomatic way of handling that in Ruby ...

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Greg Navis

@gregnavis

Mar 24, 2023

💡 Ruby meta-programming idea: final classes can be easily implemented in Ruby

I've actually published a gem whose first feature is exactly that. More on that later though. Let's understand the concept of final classes first.

Ready? Set? Go!

What's a final class?

A final class is a class that cannot be inherited from. Any attempt to subclass it would result in an error (compile-time or runtime, depending on the language).

It's a foreign concept in Ruby land, so let's have a look at other languages.

In UIKit, Apple's UI framework, there's a view controller called UIAlertController for displaying all sorts of alerts.

Technically, it's NOT final, but the documentation says it should be used as-is and not subclassed.

That would be a perfect fit for being final.

Read 12 tweets

Greg Navis

@gregnavis

Mar 8, 2023

💡 Rails tip: as_json can be used to convert models into ... no, not JSON ... into hashes

It can be useful when building and working with APIs, so it's always a good idea to understand how it works. It's implemented by Active Model and is quite generic.

Let's dive in! 🤿 😅

Called without arguments it returns a hash including all columns in the model.

Is this a good idea? NO!

⚠️ Do that in a public API and it's guaranteed you'll leak sensitive data sooner or later. Therefore, you should use this rarely, if ever.

What's the alternative?

You can whitelist or blacklist columns (and wrap the output in a hash).

My recommendation: whitelist by default, unless you're sure blacklisting is better

You may think whitelisting and blacklisting are two sides of the same coin but they are NOT!

Let's discuss why.

Read 9 tweets

Greg Navis

@gregnavis

Feb 27, 2023

💡 Ruby tip: hierarchical logger can be built in under 20 lines

Motivated by helping active_doctor_users identify specific parts of their code base that break the tool.

Logs benefit from structure, and it's trivial to add _some_ structure even if they're text-based.

Here's how

Text logs shown as a sequence of lines fail to capture the call stack structure.

If line A is followed by line B then it's difficult to tell whether B is from the same function, a caller function, a callee function, or another place entirely.

Fortunately, it's easy to fix.

Indentation can be used to introduce structure into otherwise purely text-based logs. It's like indenting source code to make it more readable.

The best part: doing that in Ruby in trivial, but elegant!

Here's what I did in active_record_doctor ...

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