Understanding Ruby's defined? Keyword and its Usage

2023/08/27

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Ruby's defined? keyword is a useful tool for checking if a variable is defined or not. It can be used with different types of expressions, such as objects, variables, and method names. The keyword returns nil if the expression cannot be resolved, and a string describing the expression if it can be resolved. This article provides examples of using defined? and highlights some common mistakes to avoid, such as using it to check hash keys. The article also discusses lazy evaluation and caching of expensive operations using the ||= operator, and how defined? can be used to optimize this process. Additionally, the article emphasizes the importance of using parentheses when using defined? to ensure clear and readable code. Overall, this article serves as a guide for developers looking to understand and utilize Ruby's defined? keyword effectively.