我有以下两种方法从数据库中获取数据：
- (void) checkAndCreateDatabase {
//Check if the database has been saved to the users phone, if not then copy it over
BOOL l_Success;
//Create a file manager object, we will use this to check the status
//of the databse and to copy it over if required
NSFileManager *l_FileManager = [NSFileManager defaultManager];
//Check if the database has already been created in the users filesystem
l_Success = [l_FileManager fileExistsAtPath:m_DatabasePath];
//If the database already exists then return without doing anything
if(l_Success)
return;
//If not then proceed to copy the database from the application to the usrs filesystem
//Get the path to the database in the application package
NSString *l_DatabasePathFromApp = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:m_DatabaseName];
//Copy the database from the package to the usrrs filesystem
[l_FileManager copyItemAtPath:l_DatabasePathFromApp toPath:m_DatabasePath error:nil];
}
和：
- (void) readProductsFromDatabase {
//Setup the database object
sqlite3 *l_Database;
//Init the products array
m_Products = [[NSMutableArray alloc] init];
//Open the database from the users filessystem
if(sqlite3_open([m_DatabasePath UTF8String], &l_Database) == SQLITE_OK) {
//Set-up the SQL statement and compile it for faster access
const char *sqlStatement = "select *from products";
sqlite3_stmt *compiledStatement;
if(sqlite3_prepare_v2(l_Database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK)
{
//Loop through the results and add them to the feeds array
while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
//Read the data from the results row
NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];
NSString *aCategory = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)];
NSString *aCalories = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 3)];
NSString *aFat = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 4)];
NSString *aSaturates = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 5)];
NSString *aSugar = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 6)];
NSString *aFibre = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 7)];
NSString *aSalt = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 8)];
NSString *aImageURL = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 9)];
NSLog(@"Delegate");
NSString *aNote = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 10)];
NSUInteger myInt = sqlite3_column_int(compiledStatement, 11);
NSString *aServes = [NSString stringWithFormat:@"%d", myInt];
//Create a new animal object with the data from the database
Product *l_Product = [[Product alloc] initWithName:aName category:aCategory calories:aCalories fat:aFat saturates:aSaturates sugar:aSugar fibre:aFibre salt:aSalt imageURL:aImageURL note:aNote serves:aServes];
//Add the animal object to the animals array
[m_Products addObject:l_Product];
}
}
//Release the compiled statement from memory
sqlite3_finalize(compiledStatement);
}
sqlite3_close(l_Database);
}
我的问题似乎是这条线：
if(sqlite3_prepare_v2(l_Database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK)
未计算为SQLITE_OK。
这是我的数据库路径：
m_DatabasePath=/Users/jacknutkins/Library/Application Support/iPhone Simulator/5.0/Applications/6F723583-9A25-4F17-AF75-911DE9CB7BD8/Library/ProductDatabase.sql
这是我的应用程序委派方法，包含相关代码：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//Set-up some globals
m_DatabaseName = @"ProductDatabase.sql";
//Get the path to the documents directory and append the databaseName
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
m_DatabasePath = [documentsDirectory stringByAppendingPathComponent:@"ProductDatabase.sql"];
//Execute the "checkAndCreateDatabase" function
[self checkAndCreateDatabase];
//Query the databse for all animal records and construct the "animals" array
[self readProductsFromDatabase];
..unrelated code..
如果有人能阐明这一点，我们将不胜感激。
Jack
编辑在m_DatabasePath路径的数据库上运行select语句后，它什么也不返回-文件是空的-知道我在代码中访问的文件的副本为什么是空的吗？
编辑2这是我的新代码：
- (void) checkAndCreateDatabase {
// First, test for existence.
NSFileManager *fileManager = [NSFileManager defaultManager];
NSError *error;
NSString *dbPath = [self getDBPath];
BOOL success = [fileManager fileExistsAtPath:dbPath];
if(!success) {
NSString *defaultDBPath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"ProductDatabase.sql"];
success = [fileManager copyItemAtPath:defaultDBPath toPath:dbPath error:&error];
if (!success)
NSAssert1(0, @"Failed to create writable database file with message '%@'.", [error localizedDescription]);
}
}
- (NSString *) getDBPath {
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory , NSUserDomainMask, YES);
NSString *documentsDir = [paths objectAtIndex:0];
return [documentsDir stringByAppendingPathComponent:@"ProductDatabase.sql"];
}
- (void) readProductsFromDatabase {
NSMutableArray *products = [[NSMutableArray alloc] init];
self.m_Products = products;
// The database is stored in the application bundle.
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *path = [documentsDirectory stringByAppendingPathComponent:@"ProductDatabase.sql"];
// Open the database. The database was prepared outside the application.
if (sqlite3_open([path UTF8String], &database) == SQLITE_OK) {
// Get the primary key for all books.
const char *sql = "SELECT * FROM products";
sqlite3_stmt *statement;
// Preparing a statement compiles the SQL query into a byte-code program in the SQLite library.
// The third parameter is either the length of the SQL string or -1 to read up to the first null terminator.
if (sqlite3_prepare_v2(database, sql, -1, &statement, NULL) == SQLITE_OK) {
// We "step" through the results - once for each row.
while (sqlite3_step(statement) == SQLITE_ROW) {
// //Read the data from the results row
NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 1)];
NSString *aCategory = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 2)];
NSString *aCalories = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 3)];
NSString *aFat = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 4)];
NSString *aSaturates = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 5)];
NSString *aSugar = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 6)];
NSString *aFibre = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 7)];
NSString *aSalt = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 8)];
NSString *aImageURL = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 9)];
NSLog(@"Delegate");
NSString *aNote = [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement, 10)];
NSUInteger myInt = sqlite3_column_int(statement, 11);
NSString *aServes = [NSString stringWithFormat:@"%d", myInt];
//Create a new animal object with the data from the database
Product *l_Product = [[Product alloc] initWithName:aName category:aCategory calories:aCalories fat:aFat saturates:aSaturates sugar:aSugar fibre:aFibre salt:aSalt imageURL:aImageURL note:aNote serves:aServes];
//
// //Add the animal object to the animals array
[m_Products addObject:l_Product];
}
}
// "Finalize" the statement - releases the resources associated with the statement.
sqlite3_finalize(statement);
} else {
// Even though the open failed, call close to properly clean up resources.
sqlite3_close(database);
NSAssert1(0, @"Failed to open database with message '%s'.", sqlite3_errmsg(database));
// Additional error handling, as appropriate...
}
}
当我运行这个时，我得到错误：
2012-03-22 13:52:29.551 TabbedDietApp[2040:fb03] *** Assertion failure in -[AppDelegate checkAndCreateDatabase], /Users/jacknutkins/Documents/TabbedDietApp/TabbedDietApp/AppDelegate.m:504
2012-03-22 13:52:29.552 TabbedDietApp[2040:fb03] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to create writable database file with message 'The operation couldn’t be completed. (Cocoa error 260.)'.'
我开始为这件事伤透了脑筋。。
编辑3我试过：
NSString*filePath=[[NSBundle mainBundle]pathForResource:@"ProductDatabase"类型：@"sql"]；
它返回nil，我不明白，因为文件在应用程序目录中。。
Noob错误，我没有选中数据库"目标成员资格"部分的复选框。谢谢大家抽出时间。
我建议您激活一些给定的调试工具：1）在对copyItemAtPath的调用中添加NSError参数。2） 将sqlite3_prepare_v2（l_Database，sqlStatement，-1，&compiledStatement，NULL）语句移到自己的行中，并检查返回值。如果你没有正确地复制文件，打开的文件会给你一个空白的DB，这似乎就是你所拥有的。
NSError * error;
BOOL copiedIt = [l_FileManager copyItemAtPath:l_DatabasePathFromApp toPath:m_DatabasePath error:&error];
以上内容至少会告诉你它是否有效。如果它不起作用，你就知道你的问题在哪里。
"从产品中选择*"真的不应该是"从产品"中选择*吗？