# diffSetsBy

open fun <T> diffSetsBy(left: Set<out T>, right: Set<out T>, compareBy: Transformer<out Any, T>): CollectionUtils.SetDiff<T>(source)

Provides a “diff report” of how the two sets are similar and how they are different, comparing the entries by some aspect. The transformer is used to generate the value to use to compare the entries by. That is, the entries are not compared by equals by an attribute or characteristic. The transformer is expected to produce a unique value for each entry in a single set. Behaviour is undefined if this condition is not met.

#### Return

A representation of the difference

#### Parameters

left

The set on the “left” side of the comparison.

right

The set on the “right” side of the comparison.

compareBy

Provides the value to compare entries from either side by

<T>

The type of the entry objects