Which transformer sorts a list of values rather than features?

• A. Sorter
• B. ListSorter
• C. Orderer
• D. StreamOrderCalculator

Answer: (B)

Sorting elements inside a list attribute versus sorting whole features is what this item is testing. In FME, a ListSorter is the transformer that reorders the items contained in a list attribute within a single feature. It changes the order of the values inside the list while leaving the feature itself intact. This is different from transformers that sort features themselves, such as the one that reorders entire features in the stream by one or more attributes, or a transformer that assigns or preserves stream order. There’s also a tool that assigns an order value to features in a stream for tracking, but that doesn’t actually sort the contents of a list. So when you need to reorder the values inside a list rather than the sequence of features, the appropriate tool is the ListSorter. For example, if a feature has a list attribute called values = [3, 1, 4, 2] and you want it as [1, 2, 3, 4], ListSorter performs that internal reordering.