ios - compile error with rows.next() in GRDB and Swift 3 -

i developing ios app using swift 3 , grdb sqlite library. following code fragment causes compile error of "value of type '[row]' has no member 'next'"

let rows = try row.fetchall(db, sql, arguments:arguments) while let row = try rows.next() {             <--- line error       ... } 

as far can tell following example in docs correctly. can tell me doing wrong?

the fetchall method returns regular swift array, iterate other arrays:

let rows = try row.fetchall(db, sql, arguments:arguments) // [row] row in rows {     // use row } 

the next method belongs cursors, fetchcursor method. cursors not arrays because don't load database results in 1 step. instead, cursors iterated row after row:

let rows = try row.fetchcursor(db, sql, arguments:arguments) // databasecursor<row> while let row = try rows.next() {     // use row } 

you see both arrays , cursors can iterate database results. how choose 1 or other? @ differences:

• arrays contain copies of database values , may consumed on thread.
• arrays can can take lot of memory, if number of fetched results high.
• arrays can iterated many times.
• cursors iterate on database results in lazy fashion, , don't consume memory.
• cursors faster because go straight sqlite , don't copy database values unless necessary.
• cursors can not used on thread.
• cursors can iterated 1 time.

compare:

// on main thread: let (rowarray, rowcursor) = try dbqueue.indatabase { db -> ([row], databasecursor<row>) in     let rowarray = try row.fetchall(db, "select ...")     let rowcursor = try row.fetchcursor(db, "select ...")      // ok     row in rowarray { ... }     while let row = try rowcursor.next() { ... }      // second iteration     row in rowarray { ... }                  // same rows     while let row = try rowcursor.next() { ... } // no result      return (rowarray, rowcursor) }  // ok: arrays can consumed on thread row in rowarray { ... } dispatchqueue.global(.default).async {     row in rowarray { ... } }  // don't that, never while let row = try rowcursor.next() { ... } dispatchqueue.global(.default).async {     while let row = try rowcursor.next() { ... } } 

if don't see, or don't care difference, use arrays. if care memory , performance, use cursors when appropriate.

link documentation: https://github.com/groue/grdb.swift/blob/master/readme.md#fetching-methods