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Objective-C iOS Development for Legacy & Enterprise Apps · Aula

Integração do SQLite com FMDB

Integre bancos de dados SQLite às suas aplicações Objective-C usando o popular adaptador FMDB para manipulação direta de dados.

Integração do SQLite com FMDB é uma aula grátis de Objective-C iOS Development for Legacy & Enterprise Apps no CoddyKit. Esta é a aula 3 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Objective-C iOS Development for Legacy & Enterprise Apps, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Objective-C iOS Development for Legacy & Enterprise Apps inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

SQLite & FMDB: An Introduction

Welcome! In this lesson, we'll explore integrating SQLite, a popular lightweight database, directly into your Objective-C applications. SQLite is embedded directly within your app, perfect for local data storage.

To make working with SQLite easier in Objective-C, we'll use FMDB, a powerful and user-friendly wrapper. It simplifies common database tasks.

Why Choose FMDB?

While you can use SQLite's C API directly, FMDB offers several advantages:

  • Object-Oriented: It provides Objective-C classes for database, result sets, and statements.
  • Simplified API: Easier to write and read than raw C code.
  • Parameter Binding: Safely handles arguments, preventing SQL injection.
  • Thread Safety: Includes FMDatabaseQueue for safe multi-threaded access.

Setting Up FMDB

To use FMDB in your project, the easiest way is via CocoaPods. Add pod 'FMDB' to your Podfile and run pod install. After installation, remember to #import "FMDB.h" in your Objective-C files.

Alternatively, you can manually drag the FMDB source files into your project.

Opening Your Database

First, you need to create or open a database file. FMDB's FMDatabase class makes this straightforward. If the file doesn't exist, it will be created.

Try running this example to open a database:

#import <Foundation/Foundation.h>
#import "FMDB.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    // Get the path to the app's Documents directory
    NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"myApp.sqlite"];

    // Create an FMDatabase object
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];

    if (![db open]) {
      NSLog(@"Error: Could not open database.");
      // Always check for errors!
      return 1;
    }
    NSLog(@"Database opened successfully at: %@", dbPath);

    // Close the database when done
    [db close];
    NSLog(@"Database closed.");
  }
  return 0;
}

Creating a Table

Once the database is open, you can execute SQL commands like CREATE TABLE using executeUpdate:. This method is used for any SQL that doesn't return a result set (e.g., INSERT, UPDATE, DELETE).

Run this code to create a 'users' table:

#import <Foundation/Foundation.h>
#import "FMDB.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"myApp.sqlite"];
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];

    if (![db open]) { NSLog(@"Error opening db."); return 1; }

    NSString *sql = @"CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)";
    BOOL success = [db executeUpdate:sql];

    if (success) {
      NSLog(@"Table 'users' created or already exists.");
    } else {
      NSLog(@"Error creating table: %@", [db lastErrorMessage]);
    }
    [db close];
  }
  return 0;
}

Inserting Data

To add data to your table, use executeUpdate: again. FMDB is great at handling parameters, preventing SQL injection. Use ? as placeholders for your values.

See how we insert two users:

#import <Foundation/Foundation.h>
#import "FMDB.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"myApp.sqlite"];
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];

    if (![db open]) { NSLog(@"Error opening db."); return 1; }
    [db executeUpdate:@"CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)"];

    BOOL success1 = [db executeUpdate:@"INSERT INTO users (name, age) VALUES (?, ?)", @"Alice", @25];
    BOOL success2 = [db executeUpdate:@"INSERT INTO users (name, age) VALUES (?, ?)", @"Bob", @30];

    if (success1 && success2) {
      NSLog(@"Users inserted successfully!");
    } else {
      NSLog(@"Error inserting users: %@", [db lastErrorMessage]);
    }
    [db close];
  }
  return 0;
}

Querying Data

To retrieve data, use executeQuery:. This returns an FMResultSet object, which you can iterate through to get your results. Each row's columns can be accessed by name or index.

Let's fetch the users we just added:

#import <Foundation/Foundation.h>
#import "FMDB.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"myApp.sqlite"];
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];

    if (![db open]) { NSLog(@"Error opening db."); return 1; }
    [db executeUpdate:@"CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)"];
    [db executeUpdate:@"INSERT INTO users (name, age) VALUES (?, ?)", @"Charlie", @28];

    FMResultSet *rs = [db executeQuery:@"SELECT id, name, age FROM users"];
    while ([rs next]) {
      int userId = [rs intForColumn:@"id"];
      NSString *name = [rs stringForColumn:@"name"];
      int age = [rs intForColumn:@"age"];
      NSLog(@"User ID: %d, Name: %@, Age: %d", userId, name, age);
    }
    [rs close]; // Always close the result set
    [db close];
  }
  return 0;
}

Updating and Deleting Data

Modifying or removing records also uses executeUpdate:. Just provide the appropriate SQL UPDATE or DELETE statements, again using ? for parameters.

This example updates 'Charlie's age and then deletes 'Bob':

#import <Foundation/Foundation.h>
#import "FMDB.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"myApp.sqlite"];
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];

    if (![db open]) { NSLog(@"Error opening db."); return 1; }
    [db executeUpdate:@"CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT, age INTEGER)"];
    [db executeUpdate:@"INSERT INTO users (name, age) VALUES (?, ?)", @"Charlie", @28];
    [db executeUpdate:@"INSERT INTO users (name, age) VALUES (?, ?)", @"Bob", @30];

    // Update Charlie's age
    BOOL updateSuccess = [db executeUpdate:@"UPDATE users SET age = ? WHERE name = ?", @29, @"Charlie"];
    if (updateSuccess) { NSLog(@"Charlie's age updated."); }

    // Delete Bob
    BOOL deleteSuccess = [db executeUpdate:@"DELETE FROM users WHERE name = ?", @"Bob"];
    if (deleteSuccess) { NSLog(@"Bob deleted."); }

    [db close];
  }
  return 0;
}

Using Transactions for Reliability

For sequences of database operations that must all succeed or all fail, use transactions. FMDB provides beginTransaction, commit, and rollback methods to ensure data integrity.

If any operation within the transaction fails, you can roll back to the state before the transaction began.

#import <Foundation/Foundation.h>
#import "FMDB.h"

int main(int argc, const char * argv[]) {
  @autoreleasepool {
    NSString *docsPath = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES)[0];
    NSString *dbPath = [docsPath stringByAppendingPathComponent:@"myApp.sqlite"];
    FMDatabase *db = [FMDatabase databaseWithPath:dbPath];

    if (![db open]) { NSLog(@"Error opening db."); return 1; }
    [db executeUpdate:@"CREATE TABLE IF NOT EXISTS products (id INTEGER PRIMARY KEY, name TEXT, price REAL)"];

    [db beginTransaction];
    BOOL success = YES;
    if (![db executeUpdate:@"INSERT INTO products (name, price) VALUES (?, ?)", @"Apple", @1.0]) {
        success = NO;
    }
    // Simulate a failure by trying to insert a bad value (e.g., duplicate PK if not autoinc)
    // For this example, let's just make the second insert conditional
    if (success && ![db executeUpdate:@"INSERT INTO products (name, price) VALUES (?, ?)", @"Orange", @1.5]) {
        success = NO;
    }

    if (success) {
        [db commit];
        NSLog(@"Transaction committed: products inserted.");
    } else {
        [db rollback];
        NSLog(@"Transaction rolled back due to error: %@", [db lastErrorMessage]);
    }
    [db close];
  }
  return 0;
}

Check Your Understanding

Which of the following statements about using FMDB for SQLite in Objective-C are true?

Recap: SQLite & FMDB

Great job! You've learned how to integrate SQLite databases into your Objective-C apps using the FMDB wrapper.

  • SQLite is a lightweight, embedded database.
  • FMDB simplifies SQLite operations with an Objective-C API.
  • You can open databases, create tables, and perform CRUD (Create, Read, Update, Delete) operations.
  • Always use parameterized queries for safety and consider transactions for reliability.

This knowledge is crucial for managing local data storage in your legacy Objective-C applications!

Perguntas Frequentes

A aula “Integração do SQLite com FMDB” é grátis?

Sim — o texto completo de “Integração do SQLite com FMDB” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de Objective-C iOS Development for Legacy & Enterprise Apps, atualize para CoddyKit PRO. O curso de Objective-C iOS Development for Legacy & Enterprise Apps inclui 4 aulas no total.

O que vou aprender em “Integração do SQLite com FMDB”?

Integre bancos de dados SQLite às suas aplicações Objective-C usando o popular adaptador FMDB para manipulação direta de dados. Você pratica Objective-C iOS Development for Legacy & Enterprise Apps com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar Objective-C iOS Development for Legacy & Enterprise Apps?

Nenhuma experiência prévia é necessária. Objective-C iOS Development for Legacy & Enterprise Apps no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 3 de 4.

Quanto tempo leva a aula “Integração do SQLite com FMDB”?

A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.

Posso escrever e executar código nesta aula de Objective-C iOS Development for Legacy & Enterprise Apps?

Sim. Cada aula de Objective-C iOS Development for Legacy & Enterprise Apps inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.

Todas as aulas deste curso

  1. Listas de Propriedades e Arquivamento
  2. Fundamentos do Core Data
  3. Integração do SQLite com FMDB
  4. Armazenar Preferências com NSUserDefaults
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