FMDB v2.7

This is an Objective-C wrapper around SQLite.

The FMDB Mailing List:

https://groups.google.com/group/fmdb

Read the SQLite FAQ:

https://www.sqlite.org/faq.html

Since FMDB is built on top of SQLite, you're going to want to read this page top to bottom at least once. And while you're there, make sure to bookmark the SQLite Documentation page: https://www.sqlite.org/docs.html

Contributing

Do you have an awesome idea that deserves to be in FMDB? You might consider pinging ccgus first to make sure he hasn't already ruled it out for some reason. Otherwise pull requests are great, and make sure you stick to the local coding conventions. However, please be patient and if you haven't heard anything from ccgus for a week or more, you might want to send a note asking what's up.

Installing

CocoaPods

FMDB can be installed using CocoaPods.

If you haven't done so already, you might want to initialize the project, to have it produce a

Podfile

$ pod init

Then, edit the

Podfile

FMDB

# Uncomment the next line to define a global platform for your project
# platform :ios, '9.0'

target 'MyApp' do
    # Comment the next line if you're not using Swift and don't want to use dynamic frameworks
    use_frameworks!
# Pods for MyApp2

pod 'FMDB'
# pod 'FMDB/FTS'   # FMDB with FTS
# pod 'FMDB/standalone'   # FMDB with latest SQLite amalgamation source
# pod 'FMDB/standalone/FTS'   # FMDB with latest SQLite amalgamation source and FTS
# pod 'FMDB/SQLCipher'   # FMDB with SQLCipher
end

Then install the pods:

$ pod install

Then open the

.xcworkspace

.xcodeproj

For more information on Cocoapods visit https://cocoapods.org.

If using FMDB with SQLCipher you must use the FMDB/SQLCipher subspec. The FMDB/SQLCipher subspec declares SQLCipher as a dependency, allowing FMDB to be compiled with the

-DSQLITE_HAS_CODEC

Carthage

Once you make sure you have the latest version of Carthage, you can open up a command line terminal, navigate to your project's main directory, and then do the following commands:

$ echo ' github "ccgus/fmdb" ' > ./Cartfile
$ carthage update

You can then configure your project as outlined in Carthage's Getting Started (i.e. for iOS, adding the framework to the "Link Binary with Libraries" in your target and adding the

copy-frameworks

Swift Package Manager

Declare FMDB as a package dependency.

swift
.package(
    name: "FMDB", 
    url: "https://github.com/ccgus/fmdb", 
    .upToNextMinor(from: "2.7.8")),

Use FMDB in target dependencies

swift
.product(name: "FMDB", package: "FMDB")

FMDB Class Reference:

https://ccgus.github.io/fmdb/html/index.html

Automatic Reference Counting (ARC) or Manual Memory Management?

You can use either style in your Cocoa project. FMDB will figure out which you are using at compile time and do the right thing.

What's New in FMDB 2.7

FMDB 2.7 attempts to support a more natural interface. This represents a fairly significant change for Swift developers (audited for nullability; shifted to properties in external interfaces where possible rather than methods; etc.). For Objective-C developers, this should be a fairly seamless transition (unless you were using the ivars that were previously exposed in the public interface, which you shouldn't have been doing, anyway!).

Nullability and Swift Optionals

FMDB 2.7 is largely the same as prior versions, but has been audited for nullability. For Objective-C users, this simply means that if you perform a static analysis of your FMDB-based project, you may receive more meaningful warnings as you review your project, but there are likely to be few, if any, changes necessary in your code.

For Swift users, this nullability audit results in changes that are not entirely backward compatible with FMDB 2.6, but is a little more Swifty. Before FMDB was audited for nullability, Swift was forced to defensively assume that variables were optional, but the library now more accurately knows which properties and method parameters are optional, and which are not.

This means, though, that Swift code written for FMDB 2.7 may require changes. For example, consider the following Swift 3/Swift 4 code for FMDB 2.6:

queue.inTransaction { db, rollback in
    do {
        guard let db == db else {
            // handle error here
            return
        }

    try db.executeUpdate("INSERT INTO foo (bar) VALUES (?)", values: [1])
    try db.executeUpdate("INSERT INTO foo (bar) VALUES (?)", values: [2])
} catch {
    rollback?.pointee = true
}
}

Because FMDB 2.6 was not audited for nullability, Swift inferred that

db

rollback

db

rollback

nil

queue.inTransaction { db, rollback in
    do {
        try db.executeUpdate("INSERT INTO foo (bar) VALUES (?)", values: [1])
        try db.executeUpdate("INSERT INTO foo (bar) VALUES (?)", values: [2])
    } catch {
        rollback.pointee = true
    }
}

Custom Functions

In the past, when writing custom functions, you would have to generally include your own

@autoreleasepool

Also, in the past, when retrieving the values passed to the function, you had to drop down to the SQLite C API and include your own

sqlite3_value_XXX

FMDatabase

valueInt

valueString

sqlite3_result_XXX

FMDatabase

resultInt

resultString

enum

valueType

SqliteValueType

Thus, you can do something like (as of Swift 3):

db.makeFunctionNamed("RemoveDiacritics", arguments: 1) { context, argc, argv in
    guard db.valueType(argv[0]) == .text || db.valueType(argv[0]) == .null else {
        db.resultError("Expected string parameter", context: context)
        return
    }

if let string = db.valueString(argv[0])?.folding(options: .diacriticInsensitive, locale: nil) {
    db.resultString(string, context: context)
} else {
    db.resultNull(context: context)
}
}

And you can then use that function in your SQL (in this case, matching both "Jose" and "José"):

SELECT * FROM employees WHERE RemoveDiacritics(first_name) LIKE 'jose'

Note, the method

makeFunctionNamed:maximumArguments:withBlock:

makeFunctionNamed:arguments:block:

API Changes

In addition to the

makeFunctionNamed

• To become consistent with the rest of the API, the methods

  objectForColumnName

  and

  UTF8StringForColumnName

  have been renamed to

  objectForColumn

  and

  UTF8StringForColumn

  .

• Note, the

  objectForColumn

  (and the associted subscript operator) now returns

  nil

  if an invalid column name/index is passed to it. It used to return

  NSNull

  .

• To avoid confusion with

  FMDatabaseQueue

  method

  inTransaction

  , which performs transactions, the

  FMDatabase

  method to determine whether you are in a transaction or not,

  inTransaction

  , has been replaced with a read-only property,

  isInTransaction

  .

• Several functions have been converted to properties, namely,

  databasePath

  ,

  maxBusyRetryTimeInterval

  ,

  shouldCacheStatements

  ,

  sqliteHandle

  ,

  hasOpenResultSets

  ,

  lastInsertRowId

  ,

  changes

  ,

  goodConnection

  ,

  columnCount

  ,

  resultDictionary

  ,

  applicationID

  ,

  applicationIDString

  ,

  userVersion

  ,

  countOfCheckedInDatabases

  ,

  countOfCheckedOutDatabases

  , and

  countOfOpenDatabases

  . For Objective-C users, this has little material impact, but for Swift users, it results in a slightly more natural interface. Note: For Objective-C developers, previously versions of FMDB exposed many ivars (but we hope you weren't using them directly, anyway!), but the implmentation details for these are no longer exposed.

URL Methods

In keeping with Apple's shift from paths to URLs, there are now

NSURL

init

Usage

There are three main classes in FMDB:

1. FMDatabase

   - Represents a single SQLite database. Used for executing SQL statements.

2. FMResultSet

   - Represents the results of executing a query on an

   FMDatabase

   .

3. FMDatabaseQueue

   - If you're wanting to perform queries and updates on multiple threads, you'll want to use this class. It's described in the "Thread Safety" section below.

Database Creation

An

FMDatabase

1. A file system path. The file does not have to exist on disk. If it does not exist, it is created for you.
2. An empty string (

   @""

   ). An empty database is created at a temporary location. This database is deleted when the

   FMDatabase

   connection is closed.

3. NULL

   . An in-memory database is created. This database will be destroyed when the

   FMDatabase

   connection is closed.

(For more information on temporary and in-memory databases, read the sqlite documentation on the subject: https://www.sqlite.org/inmemorydb.html)

NSString *path = [NSTemporaryDirectory() stringByAppendingPathComponent:@"tmp.db"];
FMDatabase *db = [FMDatabase databaseWithPath:path];

Opening

Before you can interact with the database, it must be opened. Opening fails if there are insufficient resources or permissions to open and/or create the database.

if (![db open]) {
    // [db release];   // uncomment this line in manual referencing code; in ARC, this is not necessary/permitted
    db = nil;
    return;
}

Executing Updates

Any sort of SQL statement which is not a

SELECT

CREATE

UPDATE

INSERT

ALTER

COMMIT

BEGIN

DETACH

DELETE

DROP

END

EXPLAIN

VACUUM

REPLACE

SELECT

Executing updates returns a single value, a

BOOL

YES

NO

-lastErrorMessage

-lastErrorCode

Executing Queries

A

SELECT

-executeQuery...

Executing queries returns an

FMResultSet

nil

-lastErrorMessage

-lastErrorCode

In order to iterate through the results of your query, you use a

while()

FMResultSet *s = [db executeQuery:@"SELECT * FROM myTable"];
while ([s next]) {
    //retrieve values for each record
}

You must always invoke

-[FMResultSet next]

FMResultSet *s = [db executeQuery:@"SELECT COUNT(*) FROM myTable"];
if ([s next]) {
    int totalCount = [s intForColumnIndex:0];
}
[s close];  // Call the -close method on the FMResultSet if you cannot confirm whether the result set is exhausted.

FMResultSet

• intForColumn:

• longForColumn:

• longLongIntForColumn:

• boolForColumn:

• doubleForColumn:

• stringForColumn:

• dateForColumn:

• dataForColumn:

• dataNoCopyForColumn:

• UTF8StringForColumn:

• objectForColumn:

Each of these methods also has a

{type}ForColumnIndex:

Typically, there's no need to

-close

FMResultSet

-close

FMResultSet

Closing

When you have finished executing queries and updates on the database, you should

-close

FMDatabase

[db close];

Transactions

FMDatabase

Multiple Statements and Batch Stuff

You can use

FMDatabase

NSString *sql = @"create table bulktest1 (id integer primary key autoincrement, x text);"
                 "create table bulktest2 (id integer primary key autoincrement, y text);"
                 "create table bulktest3 (id integer primary key autoincrement, z text);"
                 "insert into bulktest1 (x) values ('XXX');"
                 "insert into bulktest2 (y) values ('YYY');"
                 "insert into bulktest3 (z) values ('ZZZ');";

success = [db executeStatements:sql];
sql = @"select count() as count from bulktest1;"
       "select count() as count from bulktest2;"
       "select count(*) as count from bulktest3;";
success = [self.db executeStatements:sql withResultBlock:^int(NSDictionary *dictionary) {
    NSInteger count = [dictionary[@"count"] integerValue];
    XCTAssertEqual(count, 1, @"expected one record for dictionary %@", dictionary);
    return 0;
}];

Data Sanitization

When providing a SQL statement to FMDB, you should not attempt to "sanitize" any values before insertion. Instead, you should use the standard SQLite binding syntax:

INSERT INTO myTable VALUES (?, ?, ?, ?)

The

?

NSArray

NSDictionary

va_list

And, to use that SQL with the

?

NSInteger identifier = 42;
NSString *name = @"Liam O'Flaherty (\"the famous Irish author\")";
NSDate *date = [NSDate date];
NSString *comment = nil;

BOOL success = [db executeUpdate:@"INSERT INTO authors (identifier, name, date, comment) VALUES (?, ?, ?, ?)", @(identifier), name, date, comment ?: [NSNull null]];
if (!success) {
    NSLog(@"error = %@", [db lastErrorMessage]);
}

Note: Fundamental data types, like the

NSInteger

variable

identifier

, should be as a

NSNumber

objects, achieved by using the

@

syntax, shown above. Or you can use the

[NSNumber numberWithInt:identifier]

syntax, too.

Likewise, SQL

NULL

values should be inserted as

[NSNull null]

. For example, in the case of

comment

which might be

nil

(and is in this example), you can use the

comment ?: [NSNull null]

syntax, which will insert the string if

comment

is not

nil

, but will insert

[NSNull null]

if it is

nil

.

In Swift, you would use

executeUpdate(values:)

throws

do {
    let identifier = 42
    let name = "Liam O'Flaherty (\"the famous Irish author\")"
    let date = Date()
    let comment: String? = nil

try db.executeUpdate("INSERT INTO authors (identifier, name, date, comment) VALUES (?, ?, ?, ?)", values: [identifier, name, date, comment ?? NSNull()])
} catch {
    print("error = (error)")
}

Note: In Swift, you don't have to wrap fundamental numeric types like you do in Objective-C. But if you are going to insert an optional string, you would probably use the

comment ?? NSNull()

syntax (i.e., if it is

nil

, use

NSNull

, otherwise use the string).

Alternatively, you may use named parameters syntax:

INSERT INTO authors (identifier, name, date, comment) VALUES (:identifier, :name, :date, :comment)

The parameters must start with a colon. SQLite itself supports other characters, but internally the dictionary keys are prefixed with a colon, do not include the colon in your dictionary keys.

NSDictionary *arguments = @{@"identifier": @(identifier), @"name": name, @"date": date, @"comment": comment ?: [NSNull null]};
BOOL success = [db executeUpdate:@"INSERT INTO authors (identifier, name, date, comment) VALUES (:identifier, :name, :date, :comment)" withParameterDictionary:arguments];
if (!success) {
    NSLog(@"error = %@", [db lastErrorMessage]);
}

The key point is that one should not use

NSString

stringWithFormat

?

WHERE

SELECT

Using FMDatabaseQueue and Thread Safety.

Using a single instance of

FMDatabase

FMDatabase

So don't instantiate a single

FMDatabase

Instead, use

FMDatabaseQueue

FMDatabaseQueue

FMDatabaseQueue

First, make your queue.

FMDatabaseQueue *queue = [FMDatabaseQueue databaseQueueWithPath:aPath];

Then use it like so:

[queue inDatabase:^(FMDatabase *db) {
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", @1];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", @2];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", @3];

FMResultSet *rs = [db executeQuery:@"select * from foo"];
while ([rs next]) {
    …
}
}];

An easy way to wrap things up in a transaction can be done like this:

[queue inTransaction:^(FMDatabase *db, BOOL *rollback) {
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", @1];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", @2];
    [db executeUpdate:@"INSERT INTO myTable VALUES (?)", @3];

if (whoopsSomethingWrongHappened) {
    *rollback = YES;
    return;
}

// etc ...
}];

The Swift equivalent would be:

queue.inTransaction { db, rollback in
    do {
        try db.executeUpdate("INSERT INTO myTable VALUES (?)", values: [1])
        try db.executeUpdate("INSERT INTO myTable VALUES (?)", values: [2])
        try db.executeUpdate("INSERT INTO myTable VALUES (?)", values: [3])

    if whoopsSomethingWrongHappened {
        rollback.pointee = true
        return
    }

    // etc ...
} catch {
    rollback.pointee = true
    print(error)
}
}

(Note, as of Swift 3, use

pointee

memory

pointee

FMDatabaseQueue

FMDatabaseQueue

Note: The calls to

FMDatabaseQueue

Making custom sqlite functions, based on blocks.

You can do this! For an example, look for

-makeFunctionNamed:

Swift

You can use FMDB in Swift projects too.

To do this, you must:

1. Copy the relevant

   .m

   and

   .h

   files from the FMDB

   src

   folder into your project.

You can copy all of them (which is easiest), or only the ones you need. Likely you will need

FMDatabase

FMResultSet

FMDatabaseAdditions

FMDatabaseQueue

src

FMDB.h

Note, if you're copying all of the files from the

src

1. If prompted to create a "bridging header", you should do so. If not prompted and if you don't already have a bridging header, add one.

For more information on bridging headers, see Swift and Objective-C in the Same Project.

1. In your bridging header, add a line that says: ```objc

   import "FMDB.h"

2. Use the variations of

   executeQuery

   and

   executeUpdate

   with the

   sql

   and

   values

   parameters with

   try

   pattern, as shown below. These renditions of

   executeQuery

   and

   executeUpdate

   both

   throw

   errors in true Swift fashion.

If you do the above, you can then write Swift code that uses

FMDatabase

let fileURL = try! FileManager.default
    .url(for: .applicationSupportDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
    .appendingPathComponent("test.sqlite")

let database = FMDatabase(url: fileURL)
guard database.open() else {
    print("Unable to open database")
    return
}
do {
    try database.executeUpdate("create table test(x text, y text, z text)", values: nil)
    try database.executeUpdate("insert into test (x, y, z) values (?, ?, ?)", values: ["a", "b", "c"])
    try database.executeUpdate("insert into test (x, y, z) values (?, ?, ?)", values: ["e", "f", "g"])
let rs = try database.executeQuery("select x, y, z from test", values: nil)
while rs.next() {
    if let x = rs.string(forColumn: "x"), let y = rs.string(forColumn: "y"), let z = rs.string(forColumn: "z") {
        print("x = \(x); y = \(y); z = \(z)")
    }
}
} catch {
    print("failed: (error.localizedDescription)")
}
database.close()

History

The history and changes are availbe on its GitHub page and are summarized in the "CHANGESANDTODO_LIST.txt" file.

Contributors

The contributors to FMDB are contained in the "Contributors.txt" file.

Additional projects using FMDB, which might be interesting to the discerning developer.

• FMDBMigrationManager, A SQLite schema migration management system for FMDB: https://github.com/layerhq/FMDBMigrationManager
• FCModel, An alternative to Core Data for people who like having direct SQL access: https://github.com/marcoarment/FCModel

Quick notes on FMDB's coding style

Spaces, not tabs. Square brackets, not dot notation. Look at what FMDB already does with curly brackets and such, and stick to that style.

Reporting bugs

Reduce your bug down to the smallest amount of code possible. You want to make it super easy for the developers to see and reproduce your bug. If it helps, pretend that the person who can fix your bug is active on shipping 3 major products, works on a handful of open source projects, has a newborn baby, and is generally very very busy.

And we've even added a template function to main.m (FMDBReportABugFunction) in the FMDB distribution to help you out:

• Open up fmdb project in Xcode.
• Open up main.m and modify the FMDBReportABugFunction to reproduce your bug.
  • Setup your table(s) in the code.
  • Make your query or update(s).
  • Add some assertions which demonstrate the bug.

Then you can bring it up on the FMDB mailing list by showing your nice and compact FMDBReportABugFunction, or you can report the bug via the github FMDB bug reporter.

Optional:

Figure out where the bug is, fix it, and send a patch in or bring that up on the mailing list. Make sure all the other tests run after your modifications.

Support

The support channels for FMDB are the mailing list (see above), filing a bug here, or maybe on Stack Overflow. So that is to say, support is provided by the community and on a voluntary basis.

FMDB development is overseen by Gus Mueller of Flying Meat. If FMDB been helpful to you, consider purchasing an app from FM or telling all your friends about it.

License

The license for FMDB is contained in the "License.txt" file.

If you happen to come across either Gus Mueller or Rob Ryan in a bar, you might consider purchasing a drink of their choosing if FMDB has been useful to you.

(The drink is for them of course, shame on you for trying to keep it.)