在Objective C中打开和创建SQLite数据库

Question

我想开发一个iOS应用程序，所以我正在学习Objective C.我在我的应用程序中遵循了使用SQLite数据库的教程。 （http://www.techotopia.com/index.php/An_Example_SQLite_based_iOS_7_Application）

我有以下代码用于打开和创建我的数据库，但它不起作用！我收到消息“无法打开或创建数据库”。有人能告诉我出了什么问题吗？

- (void)viewDidLoad
{
    [super viewDidLoad];
    NSString *docsDir;
    NSArray *dirPaths;

    // Get the documents directory
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES);

    docsDir = dirPaths[0];

    // Build the patht to the database file
    _databasePath = [[NSString alloc]initWithString: [docsDir stringByAppendingPathComponent: @"contacts.db"]];

    NSFileManager *filemgr = [NSFileManager defaultManager];

    if ([filemgr fileExistsAtPath:_databasePath] == NO) {
        const char *dbpath = [_databasePath UTF8String];

        if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK) {
            char *errMsg;
            const char *sql_stmt = "CREATE TABLE IF NOT EXISTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, ADDRESS TEXT, PHONE TEXT";

            if (sqlite3_exec(_contactDB, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK) {
                _lblStatus.text = @"Failed to create table";

            }

            sqlite3_close(_contactDB);
        } else {
            _lblStatus.text = @"Failed to open or create database";
        }
    }
}

我已经包含了'libsqlite3.dylib'并将#import添加到了H文件中。

Answer 1

在您的代码中，存在一些错误

// Get the documents directory
    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES);

使用 NSDocumentDirectory 而非 NSDocumentationDirectory

我认为它会解决你的问题。 在我的建议中，您可以尝试核心数据。它更简单 你可以试试这个教程 http://www.raywenderlich.com/934/core-data-tutorial-for-ios-getting-started

这很简单，也很容易理解。

Answer 2

DBConnection.h

#import <Foundation/Foundation.h>
#import <sqlite3.h>

// database name demo.sqlite

#define DB_NAME @"demo.sqlite"//@"Conferencedata////NSLog"

@interface DBConnection : NSObject
{
    @private sqlite3 *g_database;
}

@property (nonatomic,assign,readwrite) sqlite3 *database;

+ (DBConnection *) sharedConnection;
+ (BOOL) executeQuery:(NSString *)query;
+ (NSMutableArray *) fetchResults:(NSString *)query;
+ (int) rowCountForTable:(NSString *)table where:(NSString *)where;
+ (void) errorMessage:(NSString *)msg;
+ (void) closeConnection;

- (id)initConnection;
- (void)close;

@end

DBConnection.m

#import "DBConnection.h"
#import <UIKit/UIKit.h>
#include <sys/xattr.h>

//static sqlite3_stmt *statement = nil;

@interface DBConnection (Private)
- (void) createEditableCopyOfDatabaseIfNeeded;
- (BOOL)addSkipBackupAttributeToItemAtURL:(NSURL *)URL;
- (void) initializeDatabase;
@end

@implementation DBConnection
static DBConnection *conn = NULL;

@synthesize database = g_database;

+ (DBConnection *) sharedConnection {
if (!conn) {
conn = [[DBConnection alloc] initConnection];
}
return conn;
}

#pragma mark - Static Methods

+(BOOL) executeQuery:(NSString *)query{
    BOOL isExecuted = NO;

    sqlite3 *database = [DBConnection sharedConnection].database;
    sqlite3_stmt *statement = nil;
    const char *sql = [query UTF8String];
    if (sqlite3_prepare_v2(database, sql, -1, &statement , NULL) != SQLITE_OK) {
        //NSLog(@"Error: failed to prepare agenda query statement with message '%s'.", sqlite3_errmsg(database));
        //NSString *errorMsg = [NSString stringWithFormat:@"Failed to prepare query statement - '%s'.", sqlite3_errmsg(database)];
        //[DBConnection errorMessage:errorMsg];
        //NSAssert1(0, @"Error: failed to prepare statement with message '%s'.", sqlite3_errmsg(database));
        return isExecuted;
    }

    // Execute the query.
if(SQLITE_DONE == sqlite3_step(statement)) {
        isExecuted = YES;
    }

// finlize the statement.
sqlite3_finalize(statement);
    statement = nil;

    return isExecuted;
}
+(NSMutableArray *) fetchResults:(NSString *)query{
    NSMutableArray *results = [NSMutableArray arrayWithCapacity:0];
    sqlite3 *database = [DBConnection sharedConnection].database;
    sqlite3_stmt *statement = nil;

    const char *sql = [query UTF8String];
    if (sqlite3_prepare_v2(database, sql, -1, &statement , NULL) != SQLITE_OK) {
        //NSLog(@"Error: failed to prepare fetch results statement with message '%s'.", sqlite3_errmsg(database));
        NSString *errorMsg = [NSString stringWithFormat:@"Failed to prepare query statement - '%s'.", sqlite3_errmsg(database)];
        [DBConnection errorMessage:errorMsg];
        //NSAssert1(0, @"Error: failed to prepare statement with message '%s'.", sqlite3_errmsg(database));
        return results;
    }

    while (sqlite3_step(statement) == SQLITE_ROW) {

        id value = nil;
        NSMutableDictionary *rowDict = [NSMutableDictionary dictionaryWithCapacity:0];
        for (int i = 0 ; i < sqlite3_column_count(statement) ; i++) {

            /*
if (strcasecmp(sqlite3_column_decltype(statement,i),"Boolean") == 0) {
value = [NSNumber numberWithBool:(BOOL)sqlite3_column_int(statement,i)];
} else */

            if (sqlite3_column_type(statement,i) == SQLITE_INTEGER) {
                value = [NSNumber numberWithInt:(int)sqlite3_column_int(statement,i)];
            } else if (sqlite3_column_type(statement,i) == SQLITE_FLOAT) {
                value = [NSNumber numberWithFloat:(float)sqlite3_column_double(statement,i)];   
            } else {

                if (sqlite3_column_text(statement,i) != nil) {
                    value = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement,i)];
                } else {
                    value = @"";
                }
            }

            if (value) {
                [rowDict setObject:value forKey:[NSString stringWithUTF8String:sqlite3_column_name(statement,i)]];
            }
        }

        [results addObject:rowDict];
        ////NSLog(@"rowDict -- %@", rowDict);
    }

    sqlite3_finalize(statement);
    statement = nil;

    return results;
}
+(int) rowCountForTable:(NSString *)table where:(NSString *)where{
    int tableCount = 0;
NSString *query = @"";

    if (where != nil && ![where isEqualToString:@""]) {
        query = [NSString stringWithFormat:@"SELECT COUNT(*) FROM %@ WHERE %@",
                 table,where];
    } else {
        [NSString stringWithFormat:@"SELECT COUNT(*) FROM %@",
         table];
    }

sqlite3_stmt *statement = nil;

    sqlite3 *database = [DBConnection sharedConnection].database;
    const char *sql = [query UTF8String];
    if (sqlite3_prepare_v2(database, sql, -1, &statement , NULL) != SQLITE_OK) {
        return 0;
    }

if (sqlite3_step(statement) == SQLITE_ROW) {    
        tableCount = sqlite3_column_int(statement,0);
    }

sqlite3_finalize(statement);
return tableCount;
}
+(void) errorMessage:(NSString *)msg{
    //UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"ERROR" message:msg delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    //[alert show];
    //[alert release];
}
+(void) closeConnection{
    sqlite3 *database = [DBConnection sharedConnection].database;
    if (sqlite3_close(database) != SQLITE_OK) {
        //NSAssert1(0, @"Error: failed to close database with message '%s'.", sqlite3_errmsg(g_database));
        NSString *errorMsg = [NSString stringWithFormat:@"Failed to open database with message - '%s'.", sqlite3_errmsg(database)];
        [DBConnection errorMessage:errorMsg];
    }
}
-(id) initConnection {

    self = [super init];

if (self) {
//database = g_database;
if (g_database == nil) {
// The application ships with a default database in its bundle. If anything in the application
// bundle is altered, the code sign will fail. We want the database to be editable by users,
// so we need to create a copy of it in the application's Documents directory.
[self createEditableCopyOfDatabaseIfNeeded];
// Call internal method to initialize database connection
[self initializeDatabase];
}
}
return self;
}

#pragma mark - save db

-(void)createEditableCopyOfDatabaseIfNeeded {
    // First, test for existence.
    BOOL success;
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *dbDirectory = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@", [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleDisplayName"]]];

    if (![fileManager fileExistsAtPath:dbDirectory]) {
        [fileManager createDirectoryAtPath:dbDirectory withIntermediateDirectories:NO attributes:nil error:nil];
        [self addSkipBackupAttributeToItemAtURL:[[[NSURL alloc] initFileURLWithPath:dbDirectory isDirectory:YES] autorelease]];
    }

    NSString *writableDBPath = [dbDirectory stringByAppendingPathComponent:DB_NAME];
    success = [fileManager fileExistsAtPath:writableDBPath];
if (success) return;
    // The writable database does not exist, so copy the default to the appropriate location.
    NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:DB_NAME];
    success = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
    if (!success) {
        //NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);

        NSString *errorMsg = [NSString stringWithFormat:@"Failed to create writable database file with message - %@.", [error localizedDescription]];
        [DBConnection errorMessage:errorMsg];
    }
}
-(BOOL)addSkipBackupAttributeToItemAtURL:(NSURL *)URL{
    const char* filePath = [[URL path] fileSystemRepresentation];

    const char* attrName = "com.apple.MobileBackup";
    u_int8_t attrValue = 1;

    int result = setxattr(filePath, attrName, &attrValue, sizeof(attrValue), 0, 0);
    return result == 0;
}

#pragma mark - Open the database connection and retrieve minimal information for all objects.

-(void)initializeDatabase {
    // The database is stored in the application bundle.
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);

    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *dbDirectory = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:@"%@", [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleDisplayName"]]];


    NSString *path = [dbDirectory stringByAppendingPathComponent:DB_NAME];
////NSLog(@"SQLite Root: %s", [path UTF8String]);

    // Open the database. The database was prepared outside the application.
    if (sqlite3_open([path UTF8String], &g_database) != SQLITE_OK) {
        // Even though the open failed, call close to properly clean up resources.
        sqlite3_close(g_database);
g_database = nil;
        //NSAssert1(0, @"Failed to open database with message '%s'.", sqlite3_errmsg(g_database));
        NSString *errorMsg = [NSString stringWithFormat:@"Failed to open database with message - '%s'.", sqlite3_errmsg(g_database)];
        [DBConnection errorMessage:errorMsg];
    }
}
-(void)close {

if (g_database) {
// Close the database.
if (sqlite3_close(g_database) != SQLITE_OK) {
//NSAssert1(0, @"Error: failed to close database with message '%s'.", sqlite3_errmsg(g_database));
            NSString *errorMsg = [NSString stringWithFormat:@"Failed to open database with message - '%s'.", sqlite3_errmsg(g_database)];
            [DBConnection errorMessage:errorMsg];
}
g_database = nil;
}
}

@end

用于创建表和db

[DBConnection executeQuery:@"CREATE DATABASE demo"];
        if([DBConnection executeQuery:@"CREATE TABLE IF NOT EXISTS product (id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL)"]){

        }else{
            NSLog(@"CREATE TABLE IF NOT EXISTS product (id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL)");
        }

Answer 3

您应该执行以下操作：

1）将NSDocumentationDirectory更改为代码中NSSearchPathForDirectoriesInDomains函数参数中的NSDocumentDirectory。

2）您在第一个“if”块内的代码不正确。它应该遵循：

if ([filemgr fileExistsAtPath:_databasePath] == NO)  {
// The database does not exist, so copy the default to the appropriate location.
        NSString *defaultDBPath = [[NSBundle mainBundle] pathForResource:@"contacts.db" ofType:nil];
        BOOL success = [fileManager copyItemAtPath:defaultDBPath toPath:writableDBPath error:&error];
        if (!success) {
            // Failed to copy db from bundle to documents folder.
        }
}

3）最后编写已经拥有的代码来打开数据库。

if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK) {
        char *errMsg;
        const char *sql_stmt = "CREATE TABLE IF NOT EXISTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, ADDRESS TEXT, PHONE TEXT";

        if (sqlite3_exec(_contactDB, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK) {
            _lblStatus.text = @"Failed to create table";

        }

        sqlite3_close(_contactDB);
    } else {
        _lblStatus.text = @"Failed to open or create database";
    }

Answer 4

如何在sqlite中添加save get

ViewController.h createdata     @property（强，非原子）NSString * databasePath;     @property（nonatomic）sqlite3 * contactDB;

<强> ViewController.m

- (void)viewDidLoad {
[super viewDidLoad];


NSString *docsDir;
NSArray *dirPaths;

// Get the documents directory
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,    
NSUserDomainMask, YES);
docsDir = dirPaths[0];

// Build the path to the database file
_databasePath = [[NSString alloc]initWithString: [docsDir 
stringByAppendingPathComponent:@"mithun.db"]];

NSLog(@"CREATED DB PATH :%@", _databasePath);

//temp database path
///Users/nschool/Library/Developer/CoreSimulator/Devices/D4755C93-  38F5-4F51-933D-68501B039326/data/Containers/Data/Application/2DCCFB9B-8E96-43CC-A7FC-1AB3E8627397/Documents/contacts.db

NSFileManager *filemgr = [NSFileManager defaultManager];

if ([filemgr fileExistsAtPath: _databasePath ] == NO) {

    const char *dbpath = [_databasePath UTF8String];

    //sqlite3_open(const char *filename, <#sqlite3 **ppDb#>)

    if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK) {

        char *errMsg;
        //for query
        const char *sql_stmt = "CREATE TABLE IF NOT EXISTS CONTACT    
     (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, ADDRESS TEXT,    
     PHONE TEXT)";

          //check sqlite3 connection
        if (sqlite3_exec(_contactDB, sql_stmt, NULL, NULL, &errMsg)   
       != SQLITE_OK) {
            _status.text = @"Failed to create table";
        }
        sqlite3_close(_contactDB);
    }
    else {
        _status.text = @"Failed to open/create database";
    }
   }



}

SAVEDATA

- (IBAction)saveData:(id)sender {

const char *dbpath = [_databasePath UTF8String];

sqlite3_stmt *statement;

if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK) {

    NSString *insertSQL = [NSString stringWithFormat:
            @"INSERT INTO CONTACT (name, address,      
         phone) VALUES (\"%@\", \"%@\", \"%@\")",
             _name.text, _address.text, _phone.text];

    NSLog(@"Insert query :%@", insertSQL);

    const char *insert_stmt = [insertSQL UTF8String];

    sqlite3_prepare_v2(_contactDB, insert_stmt,-1, &statement, NULL);

    if (sqlite3_step(statement) == SQLITE_DONE) {

        _status.text = @"Contact added";
        _address.text = @"";
        _phone.text = @"";

        UIAlertController *test = [UIAlertController    
     alertControllerWithTitle:@"Test" message:@"Test"  
 preferredStyle:UIAlertControllerStyleActionSheet];

        UIAlertAction *ok = [UIAlertAction actionWithTitle:@"OK"    
     style:UIAlertActionStyleDefault handler:nil];

        UIAlertAction *cancel = [UIAlertAction 
     actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel  
  handler:nil];

        [test addAction:ok];
        [test addAction:cancel];

        [self presentViewController:test animated:YES completion:nil         
 ];



    }
    else {
        _status.text = @"Failed to add contact";
    }

    sqlite3_finalize(statement);
    sqlite3_close(_contactDB);
}

}

Answer 5

·H

#import <UIKit/UIKit.h>
#import <sqlite3.h>

@interface ViewController : UIViewController<UITextFieldDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *imageviewTxt;

 @property (weak, nonatomic) IBOutlet UITextField *nameTxt;
  @property (weak, nonatomic) IBOutlet UITextField *mobilenoTxt;
   @property (weak, nonatomic) IBOutlet UITextField *destinationTxt;
 @property (weak, nonatomic) IBOutlet UILabel *status;
 - (IBAction)submit:(id)sender;
@property (strong, nonatomic) NSString *databasePath;
@property (nonatomic) sqlite3 *contactDB;

@end

Answer 6

您可以使用我的库LabQLite。它有一种非常方便的方式为您连接/打开/关闭SQLite 3数据库，所有这些都封装在面向对象的感觉中。

[LabQLiteDatabaseController activateSharedControllerWithFileFromLocalBundle:@"my_sqlite_3_database.sqlite3" toBeCopiedToAndUsedFromDirectory:@"" assumingNSDocumentDirectoryAsRootPath:YES overwrite:NO error:&error];

我还创建了一个模型生成器工具，您可以使用它来获取表示SQLite 3数据库中的表/视图的类。 LabQLite可以立即使用所述类：https://github.com/jmbarnardgh/labqlite_model_generator