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Analyze the mechanics of the Ruby Method Lookup Chain with complex multiple inheritances and prepends.

Updated May 17, 2026

Short answer

The lookup chain is strictly linear: Singleton Class -> Prepended Modules -> Current Class -> Included Modules -> Superclass -> Object -> Kernel -> BasicObject.

Deep explanation

Ruby does not support multiple class inheritance. Instead, it uses a linear ancestor path called the method lookup chain. When an object receives a message, Ruby finds its immediate singleton class. It then searches any modules prepended to that singleton class, followed by the singleton class itself. Next, it moves to modules prepended to the object's base class, the base class itself, and modules included in the base class. This structure repeats up the inheritance chain through each superclass.

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