The Ruby Programming Language

Method Names

By convention, method names begin with a lowercase letter. (Method names can begin with a capital letter, but that makes them look like constants.) When a method name is longer than one word, the usual convention is to separate the words with underscores like_this rather than using mixed case likeThis.

Method Name Resolution

This section describes the names you give to methods when you define them. A related topic is method name resolution: how does the Ruby interpreter find the definition of the method named in a method invocation expression? The answer to that question must wait until we’ve discussed classes in Ruby. It is covered in Method Lookup.

Method names may (but are not required to) end with an equals sign, a question mark, or an exclamation point. An equals sign suffix signifies that the method is a setter that can be invoked using assignment syntax. Setter methods are described in Assigning to Attributes and Array Elements and additional examples are provided in Accessors and Attributes. The question mark and exclamation point suffixes have no special meaning to the Ruby interpreter, but they are allowed because they enable two extraordinarily useful naming conventions.

The first convention is that any method whose name ends with a question mark returns a value that answers the question posed by the method invocation. The empty? method of an array, for example, returns true if the array has no elements. Methods like these are called predicates. Predicates typically ...