robertmryan
commented
10 years ago Nice.
A couple of observations:
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I'd suggest including
FMDB.hin the bridging header, instead of just those two headers. That way, with a single#import, you get everything you'd commonly need:#import "FMDB.h" - Does the adding of the SQLite library to your target's linked libraries warrant inclusion in your introduction? If someone hasn't used FMDB before, this strikes me as a good thing to include. (And if it's there, but I missed it, I apologize.)
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You describe the process of manually creating a bridging header (and, by the way, Apple advises a filename of
Module-Bridging-Header.h, whereModuleis the product module name). If, rather than dragging thesrc/fmdbfolder into your project, you drag the individual.mand.h, Xcode will automatically prompt to create the appropriately named bridging header for you.Hopefully this will be remedied before we get out of beta (that copying the folder won't create bridging header, but copying the individual files will), but I just find that currently dragging the source files into a project is more successful than dragging the folders, and it automates the creation of the shell of the bridging header.
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By the way, I'd suggest (especially in a tutorial where you're trying to illustrate best practices), always checking your error codes and retrieving meaningful descriptions. For example, instead of
let copiedBackupDb = filemanager.copyItemAtPath(backupDbPath, toPath:dbFilePath, error: nil) if (!copiedBackupDb) { return false; }I'd suggest:
var error: NSError? let copySuccessful = filemanager.copyItemAtPath(backupDbPath, toPath:dbFilePath, error: &error) if !copySuccessful { println("copy failed: \(error?.localizedDescription)") return false }or:
var error: NSError? if !filemanager.copyItemAtPath(backupDbPath, toPath:dbFilePath, error: &error) { println("copy failed: \(error?.localizedDescription)") return false }Likewise, where you might have something like:
db.executeUpdate(addQuery, withArgumentsInArray: nil)I'd suggest:
let updateSuccessful = db.executeUpdate(addQuery, withArgumentsInArray: nil) if !updateSuccessful { println("update failed: \(db.lastErrorMessage())") return false }Or:
if !db.executeUpdate(addQuery, withArgumentsInArray: nil) { println("update failed: \(db.lastErrorMessage())") return }It's just a common SQLite problem I see on Stack Overflow is a failure to check return codes and handle/detect failures properly, so if we're offering a tutorial, we might want to encourage best practices.
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If you wanted to supplement your tutorial with a
FMDatabaseQueueexample (and many of us are writing multithreaded code in whichFMDatabaseQueueis invaluable), here's an example:var queue: FMDatabaseQueue? func testDatabaseQueue() { let documentsFolder = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as String let databasePath = documentsFolder.stringByAppendingPathComponent("test.sqlite") queue = FMDatabaseQueue(path: databasePath) // create table queue?.inDatabase() { db in if !db.executeUpdate("create table test (id integer primary key autoincrement, a text)", withArgumentsInArray:nil) { println("table create failure: \(db.lastErrorMessage())") return } } // let's insert five rows queue?.inTransaction() { db, rollback in for i in 0 ..< 5 { if !db.executeUpdate("insert into test (a) values (?)", withArgumentsInArray: ["Row \(i)"]) { println("insert \(i) failure: \(db.lastErrorMessage())") rollback.initialize(true) return } } } // let's try inserting rows, but deliberately fail half way and make sure it rolls back correctly queue?.inTransaction() { db, rollback in for i in 5 ..< 10 { if !db.executeUpdate("insert into test (a) values (?)", withArgumentsInArray: ["Row \(i)"]) { println("insert \(i) failure: \(db.lastErrorMessage())") rollback.initialize(true) return } if (i == 7) { rollback.initialize(true) } } } // let's prove that only the first five rows are there queue?.inDatabase() { db in if let rs = db.executeQuery("select * from test", withArgumentsInArray:nil) { while rs.next() { println(rs.resultDictionary()) } } else { println("select failure: \(db.lastErrorMessage())") } } // let's drop that table queue?.inDatabase() { db in if !db.executeUpdate("drop table test", withArgumentsInArray:nil) { println("table drop failure: \(db.lastErrorMessage())") return } } }But this not only illustrates the use of
FMDatabaseQueue(and the non-intuitive way one sets therollbackboolean), but also the use of a class property for the database/queue (because its not advisable to constantly open and close databases, but rather open it up once and use it repeatedly).
But, please, don't take my comments as a criticism. I think the fact that you've pulled together a demonstration is wonderful. I just wanted to offer a few constructive suggestions.
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Since it took me some figuring out, thought I'd share what I've learned (avoiding issues with importing an Objective-C library) integrating FMDB/SQLite into a Swift-language project. It's a tutorial and it's available at http://metrozines.com/