Remember when we mentioned that symbols are awesome for referencing method names? Well, .respond_to? takes a symbol and returns true if an object can receive that method and false otherwise. For example,

[1, 2, 3].respond_to?(:push)

would return true, since you can call .push on an array object. However,

[1, 2, 3].respond_to?(:to_sym)

would return false, since you can’t turn an array into a symbol.



Rather than checking to see if our age variable is an integer, check to see if it will .respond_to? the .next method. (.next will return the integer immediately following the integer it’s called on, meaning 4.next will return 5.)

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