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Ruby Equality Implementation

2 posts · May 2022 – Feb 2023

What this trail covers

Shopify has evolved its understanding and implementation of equality in Ruby, distinguishing between entities and value objects. This involves correctly implementing the `==` operator to ensure reflexivity, symmetry, and transitivity, and handling type coercion where appropriate. The focus is on predictable and correct equality checks to prevent bugs and align with developer expectations.

All Shopify trails
  1. The Case Against Monkey Patching, From a Rails Core Team Member - ShopifyThis post argues against the common practice of monkey patching in Ruby, highlighting its dangers including making upgrades difficult, introducing security vulnerabilities, increasing technical debt, and negatively impacting open-source citizenship. It advocates for upstream contributions as a safer alternative and discusses refinements as a more contained but still problematic approach due to performance impacts. The post provides guidelines for when monkey patching is unavoidable, emphasizing notifying upstream maintainers and considering alternatives like upgrades or correct usage.
  2. Implementing Equality in Ruby - ShopifyThis post details the nuances of implementing equality in Ruby, covering the `==`, `#eql?`, `#equal?`, and `#===` operators. It explains the distinction between entities (identified by an explicit `id`) and value objects (identified by their attributes), providing code examples for correct implementation of the `==` operator for both. It also discusses type coercion and the properties of a correct equality implementation (reflexivity, symmetry, transitivity), including the rare exception of NaN.