我是 iPhone 开发的新手。我已经使用 mac os x 中的终端创建了数据库。现在我正在尝试使用objective- C 在 iPhone 应用程序中以编程方式创建数据库。有人可以告诉我一个很好的网站，我可以在其中查看正在运行的示例应用程序，是否有任何网站可以学习本教程？请有人帮助我。
【问题讨论】：
NSString *docsDir;
NSArray *dirPaths;
// Get the documents directory
dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];
// Build the path 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 CONTACTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT, ADDRESS TEXT, PHONE TEXT)";
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";
}
}
[filemgr release];
【讨论】：
dbpath == databasePath? contactDB 声明在哪里？
#pragma mark - SQLite
-(void)createDatabase
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
databasePath = [[NSString alloc]initWithString:[documentsDirectory stringByAppendingPathComponent:@"timings.db"]];
if ([[NSFileManager defaultManager] fileExistsAtPath:databasePath] == FALSE)
{
if (sqlite3_open([databasePath UTF8String], &timingsDatabase) == SQLITE_OK)
{
const char *sqlStatement = "CREATE TABLE IF NOT EXISTS TIMINGS (ID INTEGER PRIMARY KEY AUTOINCREMENT, TIMESTAMP TEXT, TIMING TEXT)";
char *error;
sqlite3_exec(timingsDatabase, sqlStatement, NULL, NULL, &error);
sqlite3_close(timingsDatabase);
}
}
}
-(void)storeTiming
{
if (sqlite3_open([databasePath UTF8String], &timingsDatabase) == SQLITE_OK)
{
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"HH:mm:ss.SSS"];
NSString *insertStatement = [NSString stringWithFormat:@"INSERT INTO TIMINGS (TIMESTAMP, TIMING) VALUES (\"%@\", \"%@\")", [dateFormatter stringFromDate:startDate], stopWatchLabel.text];
char *error;
sqlite3_exec(timingsDatabase, [insertStatement UTF8String], NULL, NULL, &error);
sqlite3_close(timingsDatabase);
[dateFormatter release];
}
}
-(void)getTimings
{
if (sqlite3_open([databasePath UTF8String], &timingsDatabase) == SQLITE_OK)
{
NSString *queryStatement = [NSString stringWithFormat:@"SELECT TIMESTAMP, TIMING FROM TIMINGS"];
sqlite3_stmt *statement;
if (sqlite3_prepare_v2(timingsDatabase, [queryStatement UTF8String], -1, &statement, NULL) == SQLITE_OK)
{
while (sqlite3_step(statement) == SQLITE_ROW) {
NSLog(@"Timestamp: %s Timing: %s", sqlite3_column_text(statement, 0), sqlite3_column_text(statement, 1));
}
sqlite3_finalize(statement);
sqlite3_close(timingsDatabase);
}
}
}
查看这些示例：
【讨论】：
在 xcode 中创建 Sqlite 数据库
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
[self createDb];
return YES;
}
-(void)createDb
{
NSArray *dir=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *dbPath=[NSString stringWithFormat:@"%@/userDb.sqlite",[dir lastObject]];
sqlite3 *db;
NSFileManager *fm=[NSFileManager new];
if([fm fileExistsAtPath:dbPath isDirectory:nil])
{
NSLog(@"Database already exists..");
return;
}
if (sqlite3_open([dbPath UTF8String],&db)==SQLITE_OK)
{
const char *query="create table user (userName VARCHAR(20),userAdd VARCHAR(20), userPass VARCHAR(20))";
if (sqlite3_exec(db, query, NULL, NULL, NULL)==SQLITE_OK)
{
NSLog(@"User table created successfully..");
}else
{
NSLog(@"User table creation failed..");
}
}else
{
NSLog(@"Open table failed..");
}
sqlite3_close(db);
}
【讨论】：
如果您想使用 Database for Data Persistance，请查看 CoreData，它是为应用存储大量数据的好资源，但请记住，CoreData 不是数据库。
您可以在 iOS 平台上非常轻松地使用 SQLite，但没有像使用 CoreData 那样为您提供开发它的可视化工具
如果您存储的数据量较小，请考虑将信息存储到 plist 中。
如果你要存储一些字符串、整数或布尔值，你应该使用 NSUserDefaults
如果没有更多信息，我无法确定最适合您的方法
其他资源：
【讨论】：
为您的 iPhone 应用程序创建数据库有点冗长，但它有很多步骤，但非常简单：
首先，您应该下载 mozilla fire fox 并下载其附加组件，您可以通过单击工具选项找到 sqlite 数据库选项。您可以创建一个包含列和行的新数据库文件。创建数据库文件的过程很简单，之后您可以将该文件包含到您的 X 代码项目中。
例如：- 就像您通常包含在 Xcode 项目中的图像一样。
之后编写以下代码对我来说很好:)
在你的 . m文件写入如下sqlite代码
#import "YourHeaderFile"
static sqlite3 *database = nil;
static sqlite3_stmt *addStmt = nil;
static sqlite3_stmt *updateStmt = nil;
@implementation 'YourImplementClass'
- (NSString *) getDBPath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
return [documentsDir stringByAppendingPathComponent:@"YourDataBaseFileName.sqlite"];
}
- (void) insertValueToDatabase {
NSString *dbPath =[self getDBPath];
NSString *select_Meal = dummy_select_Meal;
NSString *dateTime = dummy_date_Time;
NSString *location = dummy_location;
NSString *mealItem = dummy_mealItem;
if (sqlite3_open([dbPath UTF8String], &database) == SQLITE_OK) {
const char *sqlDB = "Insert into iHad(Mealtype,DateAndTime,Location,Mealitem) VALUES (?,?,?,?)";
if(sqlite3_prepare_v2(database, sqlDB, -1, &addStmt, NULL) != SQLITE_OK)
NSAssert1(0, @"Error while creating add statement. '%s'", sqlite3_errmsg(database));
sqlite3_bind_text(addStmt, 1, [select_Meal UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(addStmt, 2, [dateTime UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(addStmt, 3, [location UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(addStmt, 4, [mealItem UTF8String], -1, SQLITE_TRANSIENT);
if(SQLITE_DONE != sqlite3_step(addStmt))
NSAssert1(0, @"Error while inserting data. '%s'", sqlite3_errmsg(database));
//else
//SQLite provides a method to get the last primary key inserted by using sqlite3_last_insert_rowid
//coffeeID = sqlite3_last_insert_rowid(database);
//Reset the add statement.
sqlite3_reset(addStmt);
}
else
sqlite3_close(database);
}
为了省钱，你可以创建一个这样的方法
-(void)saveButtonClick
{
if (![dummy_select_Meal length] || ![dummy_mealItem length])
{
UIAlertView *alert = [[UIAlertView alloc] init];
[alert setTitle:@"Select Meal Type/Meal Item"];
[alert setDelegate:self];
[alert addButtonWithTitle:@"Ok"];
[alert show];
[alert release];
}
else
{
indicator = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(30,30,50,50)];
indicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray;//UIActivityIndicatorViewStyleWhiteLarge;//
[self insertValueToDatabase];-----------------------> To insert data into data base
iHadAppDelegate *delegate = [[UIApplication sharedApplication]delegate];
[delegate readMealsFromDatabase];
[rootController reloadTable_SaveButton];
}
[rootController showTablePopupAction:nil];
}
如果您有任何问题，请回复我，我会帮助您:)
【讨论】：
在 didFinishLaunchingWithOptions 处调用此函数：
-(void)createdb
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *dbPath = [documentsDirectory stringByAppendingPathComponent:@"emp.sqlite"];
NSURL *dbURL = [NSURL fileURLWithPath:dbPath];
// copy a database from the bundle if not present
// on disk
NSFileManager *fm = [NSFileManager defaultManager];
if (![fm fileExistsAtPath:dbPath])
{
NSURL *bundlePath = [[NSBundle mainBundle] URLForResource:@"emp" withExtension:@"sqlite"];
NSError *error = nil;
if (!bundlePath || ![fm copyItemAtURL:bundlePath toURL:dbURL error:&error])
{
NSLog(@"error copying database from bundle: %@", error);
}
}
else
{
NSLog(@"Success in Copy file");
}
}
【讨论】：
在内存警告后调用此函数。
-(IBAction)saveData:(UIButton *)sender {
sqlite3_stmt *statement;
const char *dbPath = [databasePath UTF8String];
if(sqlite3_open(dbPath, &contactDB)== SQLITE_OK){
NSString *insertSQL = [NSString stringWithFormat:@"INSERT INTO CONTACTS(NAME,ADDRESS,PHONE)VALUES(\"%@\",\"%@\",\"%@\")",_name.text,_address.text,_phoneNo.text];
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";
_name.text = @"";
_address.text = @"";
_phoneNo.text = @"";
}else{
_status.text = @"Failed to add contact";
}
sqlite3_finalize(statement);
sqlite3_close(contactDB);
}
}
【讨论】：