Numbered params are implicitly defined block parameters intended to simplify writing short blocks. (source)

Currently (up to Ruby 3.3), names from _1 to _9 are supported to be used as numbered block params. Ruby 3.4 will introduce it as an alternative for _1.

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You will see code samples where numbered block params seem to fit and some cases where it can be harder to understand what’s happening.
I will compare before and after code and analyze cases where the readability increases, or is hurt by using the numbered block params.

A shorthand syntax for methods consisting of exactly one expression (source)

An endless method is a way to write a Ruby method on a single line with a syntax like def name = body without the need to use the end keyword.

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You will see a code sample where I think the endless method helps make the code concise and easy to read. I explain when not to use it and when it will do something different than intended due to the operators’ priority.

You will read before and after code to decide when to use it and when not to. I will share with examples the three benefits I discovered about endless methods: keeping small utility methods small, protecting against method gravity, and helping thinking in small incremental changes.

Hash values can be omitted, meaning that value will be fetched from the context by the name of the key (source)

Hash literal value omission is a feature that allows you to omit the value of a hash key when the value is available in the current scope.

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You will discover how hash literal value omission works (the scopes where it will try to find the values based on key name).
You can read code samples where hash literal value omission can simplify the code and make it easy to change. I showcase where using it might not make the code clearer, so it is best to avoid it.

Pattern matching is a feature allowing deep matching of structured values: checking the structure and binding the matched parts to local variables. (source)

Pattern matching is a feature that allows you to match and destructure objects in a single expression. It comes with a standalone operator => and a case/in syntax.

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You will discover examples of using pattern matching implemented in the two ways that Ruby supports: using case/in and using the standalone operator <expression> => <pattern> I will explore using => as the left-hand assignment operator and case/in to match and unpack objects to values conditionally.

I will present cases where this can be useful when writing Rails code, using matching by object type, a combination of patterns using the | operator, and matching your own objects by implementing destruct_keys and destruct.

This will be split over multiple emails, each focused on a use case, explaining the code and its benefits, while discussing readability, brevity, and verbosity.

Object shapes are a technique for representing properties of an object. (…) Each shape represents a specific set of attributes (instance variables and other properties) and their values. In our implementation, all objects have a shape. The shapes are nodes in a tree data structure. Every edge in the tree represents an attribute transition (source)

Object Shapes is a performance optimization that uses a tree structure to improve how Ruby VM stores and looks up instance variables. YJIT and Ruby 3.3 use the object shapes to add more improvements and performance optimizations.

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You will see examples of how to transform your code to take advantage of object shapes and minimize the number of different created shapes or object shape transitions while running your code.
It will have examples of how to declare instance variables and how to do memoization so you keep your code shape-friendly.

Between Ruby 2.7 and Ruby 3.3, there are a lot of changes to core classes or stdlib: new methods are added, other methods are improved, or there are changes in how they handle some cases.

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I will cover Range, Set, Filesystem and IOIO, Class and Module, String, Hash (and Enumerator in general), Time, Ractors, and more.

This topic is split into multiple emails, each explaining the change and showing code examples for using it. The focus is to show how to use these in production-like code.