fmdb

by ccgus

ccgus /fmdb

A Cocoa / Objective-C wrapper around SQLite

13.4K Stars 2.8K Forks Last release: 5 months ago (2.7.7) Other 605 Commits 22 Releases

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FMDB v2.7

CocoaPods Compatible Carthage Compatible

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
template for you:
$ pod init

Then, edit the

Podfile
, adding
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
rather than the
.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
flag.

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
script; in macOS, adding the framework to the list of "Embedded Binaries").

Swift Package Manager

Declare FMDB as a package dependency.

swift
.package(
    name: "FMDB", 
    url: "https://github.com/ccgus/fmdb", 
    .upToNextMinor(from: "2.7.7")),

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
and
rollback
were optionals. But, now, in FMDB 2.7, Swift now knows that, for example, neither
db
nor
rollback
above can be
nil
, so they are no longer optionals. Thus it becomes:
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
block to avoid problems when writing functions that scanned through a large table. Now, FMDB will automatically wrap it in an autorelease pool, so you don't have to.

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
calls. There are now
FMDatabase
methods,
valueInt
,
valueString
, etc., so you can stay within Swift and/or Objective-C, without needing to call the C functions yourself. Likewise, when specifying the return values, you no longer need to call
sqlite3_result_XXX
C API, but rather you can use
FMDatabase
methods,
resultInt
,
resultString
, etc. There is a new
enum
for
valueType
called
SqliteValueType
, which can be used for checking the type of parameter passed to the custom function.

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:
has been renamed to
makeFunctionNamed:arguments:block:
, to more accurately reflect the functional intent of the second parameter.

API Changes

In addition to the

makeFunctionNamed
noted above, there are a few other API changes. Specifically,
  • 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
renditions of the various
init
methods, previously only accepting paths.

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
is created with a path to a SQLite database file. This path can be one of these three:
  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
statement qualifies as an update. This includes
CREATE
,
UPDATE
,
INSERT
,
ALTER
,
COMMIT
,
BEGIN
,
DETACH
,
DELETE
,
DROP
,
END
,
EXPLAIN
,
VACUUM
, and
REPLACE
statements (plus many more). Basically, if your SQL statement does not begin with
SELECT
, it is an update statement.

Executing updates returns a single value, a

BOOL
. A return value of
YES
means the update was successfully executed, and a return value of
NO
means that some error was encountered. You may invoke the
-lastErrorMessage
and
-lastErrorCode
methods to retrieve more information.

Executing Queries

A

SELECT
statement is a query and is executed via one of the
-executeQuery...
methods.

Executing queries returns an

FMResultSet
object if successful, and
nil
upon failure. You should use the
-lastErrorMessage
and
-lastErrorCode
methods to determine why a query failed.

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

while()
loop. You also need to "step" from one record to the other. With FMDB, the easiest way to do that is like this:
FMResultSet *s = [db executeQuery:@"SELECT * FROM myTable"];
while ([s next]) {
    //retrieve values for each record
}

You must always invoke

-[FMResultSet next]
before attempting to access the values returned in a query, even if you're only expecting one:
FMResultSet *s = [db executeQuery:@"SELECT COUNT(*) FROM myTable"];
if ([s next]) {
    int totalCount = [s intForColumnIndex:0];
}

FMResultSet
has many methods to retrieve data in an appropriate format:
  • intForColumn:
  • longForColumn:
  • longLongIntForColumn:
  • boolForColumn:
  • doubleForColumn:
  • stringForColumn:
  • dateForColumn:
  • dataForColumn:
  • dataNoCopyForColumn:
  • UTF8StringForColumn:
  • objectForColumn:

Each of these methods also has a

{type}ForColumnIndex:
variant that is used to retrieve the data based on the position of the column in the results, as opposed to the column's name.

Typically, there's no need to

-close
an
FMResultSet
yourself, since that happens when either the result set is exhausted. However, if you only pull out a single request or any other number of requests which don't exhaust the result set, you will need to call the
-close
method on the
FMResultSet
.

Closing

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

-close
the
FMDatabase
connection so that SQLite will relinquish any resources it has acquired during the course of its operation.
[db close];

Transactions

FMDatabase
can begin and commit a transaction by invoking one of the appropriate methods or executing a begin/end transaction statement.

Multiple Statements and Batch Stuff

You can use

FMDatabase
's executeStatements:withResultBlock: to do multiple statements in a string:
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

?
character is recognized by SQLite as a placeholder for a value to be inserted. The execution methods all accept a variable number of arguments (or a representation of those arguments, such as an
NSArray
,
NSDictionary
, or a
va_list
), which are properly escaped for you.

And, to use that SQL with the

?
placeholders from Objective-C:
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:)
, which not only is a concise Swift syntax, but also
throws
errors for proper error handling:
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
method
stringWithFormat
to manually insert values into the SQL statement, itself. Nor should one Swift string interpolation to insert values into the SQL. Use
?
placeholders for values to be inserted into the database (or used in
WHERE
clauses in
SELECT
statements).

Using FMDatabaseQueue and Thread Safety.

Using a single instance of

FMDatabase
from multiple threads at once is a bad idea. It has always been OK to make a
FMDatabase
object per thread. Just don't share a single instance across threads, and definitely not across multiple threads at the same time. Bad things will eventually happen and you'll eventually get something to crash, or maybe get an exception, or maybe meteorites will fall out of the sky and hit your Mac Pro. This would suck.

So don't instantiate a single

FMDatabase
object and use it across multiple threads.

Instead, use

FMDatabaseQueue
. Instantiate a single
FMDatabaseQueue
and use it across multiple threads. The
FMDatabaseQueue
object will synchronize and coordinate access across the multiple threads. Here's how to use it:

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
. But in Swift 2.3, use
memory
rather than
pointee
.)

FMDatabaseQueue
will run the blocks on a serialized queue (hence the name of the class). So if you call
FMDatabaseQueue
's methods from multiple threads at the same time, they will be executed in the order they are received. This way queries and updates won't step on each other's toes, and every one is happy.

Note: The calls to

FMDatabaseQueue
's methods are blocking. So even though you are passing along blocks, they will not be run on another thread.

Making custom sqlite functions, based on blocks.

You can do this! For an example, look for

-makeFunctionNamed:
in main.m

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
and
FMResultSet
at a minimum.
FMDatabaseAdditions
provides some very useful convenience methods, so you will likely want that, too. If you are doing multithreaded access to a database,
FMDatabaseQueue
is quite useful, too. If you choose to not copy all of the files from the

src
directory, though, you may want to update
FMDB.h
to only reference the files that you included in your project.

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

src
folder into to your project (which is recommended), you may want to drag the individual files into your project, not the folder, itself, because if you drag the folder, you won't be prompted to add the bridging header (see next point).
  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
. For example, as of Swift 3:
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.)

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