RowAdapter

Row adapters present database rows in the way expected by the row consumers.

For example, when a row consumer expects a column named “consumed”, but the raw row has a column named “produced”, the ColumnMapping row adapter comes in handy:

// Feeds the "consumed" column from "produced":
let adapter = ColumnMapping(["consumed": "produced"])
let sql = "SELECT 'Hello' AS produced"
let row = try Row.fetchOne(db, sql: sql, adapter: adapter)!

// [consumed:"Hello"]
print(row)

// "Hello"
print(row["consumed"])

The raw fetched columns are not lost (see unadapted):

// ▿ [consumed:"Hello"]
//   unadapted: [produced:"Hello"]
print(row.debugDescription)

// [produced:"Hello"]
print(row.unadapted)

There are several situations where row adapters are useful. Among them:

• Adapters help disambiguate columns with identical names, which may happen when you select columns from several tables. See splittingRowAdapters(columnCounts:) for some sample code.

• Adapters help when SQLite outputs unexpected column names, which may happen with some subqueries. See RenameColumnAdapter for an example.

Splitting a Row into Chunks

• func splittingRowAdapters(columnCounts: [Int]) -> [any RowAdapter]

  Returns an array of row adapters that split a row according to the provided numbers of columns.

Adding Scopes to an Adapter

• func addingScopes([String : any RowAdapter]) -> any RowAdapter

  Returns an adapter based on self, with added scopes.

Built-in Adapters

• struct ColumnMapping

  ColumnMapping is a row adapter that maps column names.

• struct EmptyRowAdapter

  EmptyRowAdapter is a row adapter that hides all columns.

• struct RangeRowAdapter

  RangeRowAdapter is a row adapter that only exposes a range of columns.

• struct RenameColumnAdapter

  RenameColumnAdapter is a row adapter that renames columns.

• struct ScopeAdapter

  ScopeAdapter is a row adapter that defines row scopes.

• struct SuffixRowAdapter

  SuffixRowAdapter hides the leftmost columns in a row.