How deeply does The Well-Grounded Rubyist, Fourth Edition cover instance_methods?

Defines inherited and direct-only queries, visibility variants, and list intersection, but stops short of method implementation details.

Instance_methods

As explained in The Well-Grounded Rubyist, Fourth Edition

instance_methods is a Ruby Module method that returns the public and protected instance methods available from a class or module, optionally including inherited and included methods.

instance_methods is a Ruby Module method for asking a class or module which public and protected instance methods its instances can use. With no argument, it includes methods supplied by the queried object and its ancestors. section 7.7.2 section 15.2.3

Choose the query according to the method set you need:

Use instance_methods(false) to restrict the result to methods defined directly by the class or module, excluding ancestors. section 7.7.3
Use public_instance_methods, a synonym for instance_methods, or choose protected_instance_methods and private_instance_methods for visibility-specific lists. section 7.7.3 section 15.2.3
Use set intersection between two lists to find methods that one class or module defines in common with another. section 15.2.3

Inspecting Range and Enumerable

Range.instance_methods(false).sort lists methods defined directly on Range. Intersecting that list with Enumerable.instance_methods(false) identifies methods such as count, entries, first, include?, max, min, and to_a that Range redefines from Enumerable. section 15.2.3

>> Range.instance_methods(false).sort & 
➥ Enumerable.instance_methods(false)
=> [:count, :entries, :first, :include?, :max, :member?, :min, :minmax,
 :reverse_each, :to_a]

The executable IRB listing makes direct-definition filtering and method-list intersection concrete. section 15.2.3

How The Well-Grounded Rubyist, Fourth Edition covers it

Cover of The Well-Grounded Rubyist, Fourth Edition

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Related concepts

public_instance_methodsequivalent to · public_instance_methods is a Ruby Module method that returns the public instance methods available from a class or module, optionally including inherited and included methods.
methodsequivalent to · A language-level introspection facility that reports methods associated with an object or function.
ancestorcontrasts with · An ancestor is an entity higher in a hierarchical structure, reached by repeatedly following parent relationships toward the root.
singleton methodcontrasts with · A singleton method is a method defined on one particular Ruby object rather than generally on all instances of its class.
moduleuses · A module is a distinct, bounded software unit that groups related code or functionality and provides an organizational or interaction boundary within a larger system.

This explainer was generated by Manning's knowledge graph from the text of The Well-Grounded Rubyist, Fourth Edition. The section links point to the parts of the book it draws on.