B4J Code Snippet [B4X] [ListOfArrays] Sorting by multiple columns

Example of sorting a table by 2 or more columns.

Data:

Dim loa As ListOfArrays = LOAUtils.CreateEmpty(Array("Last Name", "First Name", "Age", "Favorite Color"))
loa.AddRow(Array("Smith", "John", 32, "Blue"))
loa.AddRow(Array("Smith", "Emily", 27, "Green"))
loa.AddRow(Array("Smith", "Michael", 41, "Red"))

loa.AddRow(Array("Brown", "Sarah", 35, "Purple"))
loa.AddRow(Array("Brown", "Daniel", 29, "Orange"))
loa.AddRow(Array("Brown", "Laura", 38, "Yellow"))

loa.AddRow(Array("Taylor", "James", 24, "Black"))
loa.AddRow(Array("Taylor", "Olivia", 31, "Pink"))
loa.AddRow(Array("Taylor", "David", 45, "Gray"))
loa.AddRow(Array("Taylor", "Emma", 26, "White"))

We want it to be sorted by last name and then first name if last names are identical.

The super sophisticated trick - we sort the table starting with the least important column and up to the primary column:

loa.Sort("First Name") 'first we sort the secondary column
loa.Sort("Last Name") 'and then we sort the primary column
Log(loa.ToString(0))

Output:


Last Name First Name Age Favorite Color (#rows=10, #cols=4)
-----------------------------
Brown Daniel 29 Orange
Brown Laura 38 Yellow
Brown Sarah 35 Purple
Smith Emily 27 Green
Smith John 32 Blue
Smith Michael 41 Red
Taylor David 45 Gray
Taylor Emma 26 White
Taylor James 24 Black
Taylor Olivia 31 Pink

Dependence: ListOfArrays v1.01+ (B4i only). In older versions the sorting method isn't guaranteed to be stable in regards to handling of equal values.