Avoid unnecessary disjunctive assignments in constructor


ID: ruby-best-practices/disjunctive-assign-in-const

Language: Ruby

Severity: Notice

Category: Best Practices


This rule pertains to the practice of avoiding unnecessary disjunctive (or conditional) assignments in class constructors in Ruby. A disjunctive assignment, denoted by ||=, is a shorthand way of saying “if this variable is nil or false, assign it this value; otherwise, leave it as it is.” While this can be a useful tool in some instances, using it in a class constructor can lead to confusing and unexpected behavior.

The main reason to avoid this practice is that it can lead to unexpected values for instance variables. In the non-compliant code example, if @foo somehow has a value before the constructor is called, that value will be preserved instead of being set to 42 as might be expected. This can make debugging more difficult and lead to subtle, hard-to-find bugs.

To avoid this issue, assign the value directly in the constructor, as shown in the compliant code example. This ensures that the instance variable will always have the expected value when the constructor is finished. It’s a small change, but it can make your code much easier to understand and debug.

Non-Compliant Code Examples

def initialize
  @foo ||= 42

Compliant Code Examples

def initialize
  @foo = 42
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