A method can specify default values for the last arguments:
class Person def become_older(by = 1) @age += by end end john = Person.new "John" john.age #=> 0 john.become_older john.age #=> 1 john.become_older 2 john.age #=> 3
All arguments can also be specified, in addition to their position, by their name. For example:
john.become_older by: 5
When there are many arguments, the order of the names in the invocation doesn't matter, as long as all required arguments are covered:
def some_method(x, y = 1, z = 2, w = 3) # do something... end some_method 10 # x: 10, y: 1, z: 2, w: 3 some_method 10, z: 10 # x: 10, y: 1, z: 10, w: 3 some_method 10, w: 1, y: 2, z: 3 # x: 10, y: 2, z: 3, w: 1 some_method y: 10, x: 20 # x: 20, y: 10, z: 2, w: 3 some_method y: 10 # Error, missing argument: x
When a method specifies a splat (explained in the next section), named arguments can't be used. The reason is that understanding how arguments are matched becomes very difficult; positional arguments are easier to reason about in this case.
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