Lint-UnexpectedBlockArity.md

Pattern: Unexpected block arity

Issue: -

Description

This rule checks for a block that is known to need more positional block arguments than are given (by default this is configured for Enumerable methods needing 2 arguments). Optional arguments are allowed, although they don't generally make sense as the default value will be used. Blocks that have no receiver, or take splatted arguments (ie. *args) are always accepted.

Keyword arguments (including **kwargs) do not get counted towards this, as they are not used by the methods in question.

NOTE: This rule matches for method names only and hence cannot tell apart methods with same name in different classes.

Method names and their expected arity can be configured like this:

Methods: inject: 2 reduce: 2

Examples

# bad
values.reduce {}
values.min { |a| a }
values.sort { |a; b| a + b }

# good
values.reduce { |memo, obj| memo << obj }
values.min { |a, b| a <=> b }
values.sort { |*x| x[0] <=> x[1] }

Configurable attributes

Name	Default value	Configurable values
Methods	{"chunk_while"=>2, "each_with_index"=>2, "each_with_object"=>2, "inject"=>2, "max"=>2, "min"=>2, "minmax"=>2, "reduce"=>2, "slice_when"=>2, "sort"=>2}

Further Reading

• RuboCop - Lint/UnexpectedBlockArity