Ruby Gotchas that will come back to haunt you

The page gathers common Ruby pitfalls and recommends habits that avoid confusion and bugs. It focuses on places where Ruby does something different from what many developers expect, especially in control flow, comparison, inheritance, scope, and method visibility.

Reading notes

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• and / or do not behave like && / ||; the keyword versions have lower precedence, so the safe practice is to use only && / ||.
• eql?, equal?, and === are different from ==; the page recommends using == unless there is a specific reason to compare differently.
• super without parentheses passes the original method arguments to the parent method, while super() calls the parent with no arguments.
• Custom exceptions should inherit from StandardError or a descendant, and rescue Exception should be avoided.
• class Foo::Bar does not create the same lexical scope as module Foo; class Bar; the longer nested form keeps access to constants from the enclosing module.
• Many bang! methods return nil when they make no change, so their return value should not be used in conditionals or control flow.
• An assignment method like attribute=(value) returns the assigned value, not the explicit return value from inside the method.
• private does not make self.method private; use private_class_method or define the method inside class << self.
• The closing note says these issues can look minor at first, but they can create serious headaches during Ruby on Rails development.