Style-RedundantSort.md

Pattern: Redundant sort

Issue: -

Description

This rule is used to identify instances of sorting and then taking only the first or last element. The same behavior can be accomplished without a relatively expensive sort by using Enumerable#min instead of sorting and taking the first element and Enumerable#max instead of sorting and taking the last element. Similarly, Enumerable#min_by and Enumerable#max_by can replace Enumerable#sort_by calls after which only the first or last element is used.

Examples

# bad
[2, 1, 3].sort.first
[2, 1, 3].sort[0]
[2, 1, 3].sort.at(0)
[2, 1, 3].sort.slice(0)

# good
[2, 1, 3].min

# bad
[2, 1, 3].sort.last
[2, 1, 3].sort[-1]
[2, 1, 3].sort.at(-1)
[2, 1, 3].sort.slice(-1)

# good
[2, 1, 3].max

# bad
arr.sort_by(&:foo).first
arr.sort_by(&:foo)[0]
arr.sort_by(&:foo).at(0)
arr.sort_by(&:foo).slice(0)

# good
arr.min_by(&:foo)

# bad
arr.sort_by(&:foo).last
arr.sort_by(&:foo)[-1]
arr.sort_by(&:foo).at(-1)
arr.sort_by(&:foo).slice(-1)

# good
arr.max_by(&:foo)

Further Reading

• RuboCop - Performance/RedundantSort