sqlite3 blob问题

Question

可能重复:
sqlite3在数据库中插入并读取BLOB数据

我尝试将BLOB数据读写到数据库.但是当我尝试读取blob数据时 - 它的大小为0.并且我的所有字段数据都移动了.这是代码:

请帮助我,我做错了什么？感谢名单!

-(int) addUser: (MyData *) user table: (NSString *) tableName

{

sqlite3_stmt *updStmt =nil; 

const char *sql = "INSERT INTO Users (Name, Surname, Email, Phone, Image) VALUES (?, ?, ?, ?, ?);";
int res = SQLITE_ERROR;
res = sqlite3_prepare_v2(database, sql, -1, &updStmt, NULL);

if(res!= SQLITE_OK)
{
    NSLog(@"Error while creating update statement:%@", sqlite3_errmsg(database));
    return res;
}

res = sqlite3_bind_text(updStmt, 1, [user.name UTF8String], -1, SQLITE_TRANSIENT);
res = sqlite3_bind_text(updStmt, 2, [user.surname UTF8String], -1, SQLITE_TRANSIENT);  
res = sqlite3_bind_text(updStmt, 3, [user.email UTF8String], -1, SQLITE_TRANSIENT);
res = sqlite3_bind_text(updStmt, 4, [user.telephone UTF8String], -1, SQLITE_TRANSIENT); 

NSData *imageData = [NSData dataWithData: UIImagePNGRepresentation(user.image)];
res = sqlite3_bind_blob(updStmt, 5, imageData, -1, SQLITE_BLOB);

if((res = sqlite3_step(updStmt)) != SQLITE_DONE)
{
    NSLog(@"Error while updating: %@", sqlite3_errmsg(database));
    sqlite3_reset(updStmt);
    return res;
} 

sqlite3_reset(updStmt);

return res;

}

在这里我该如何阅读这些字段:

-(MyData *) createUserWithDetailsByID: (int) uID
{
    NSString *query = [NSString stringWithFormat: @SELECT_USER_ALLDATA_BY_ID, uID];
    MyData *user = nil;

    sqlite3_stmt *statement;
    int res = SQLITE_ERROR;
    res = sqlite3_prepare_v2 (database, [query UTF8String], -1, &statement, nil);

    if (res == SQLITE_OK)
    {
        if (sqlite3_step(statement) == SQLITE_ROW)
        {
            //if there are results in row
            char *buf = NULL;
            user = [[MyData alloc] init];

            int num = sqlite3_column_int(statement, 0);
            user.uID = num;

            buf = (char *)sqlite3_column_text(statement, 1);
            if (buf)
                user.name = [NSString stringWithFormat: @"%s", buf];
            else
                user.name = @"";    

            buf = (char *)sqlite3_column_text(statement, 2);
            if (buf)
                user.surname = [NSString stringWithFormat: @"%s", buf];
            else
                user.surname = @"";

            buf = (char *)sqlite3_column_text(statement, 3);
            if (buf)
                user.email = [NSString stringWithFormat: @"%s", buf];
            else
                user.email = @"";

            buf = (char *)sqlite3_column_text(statement, 4);
            if (buf)
                user.telephone = [NSString stringWithFormat: @"%s", buf];
            else
                user.telephone = @"";

            int len = 0;
            len = sqlite3_column_bytes(statement, 5);

            NSData *imgData = [[NSData alloc] initWithBytes: sqlite3_column_blob(statement, 5) length: len];           

            UIImage *i;
            [i initWithData:imgData];

        }
    }
    sqlite3_finalize(statement);

    return user; 
}

Answer 1

NSData *imageData = [NSData dataWithData: UIImagePNGRepresentation(user.image)];
res = sqlite3_bind_blob(updStmt, 5, [imageData bytes], [imageData length], SQLITE_BLOB);

我想在你写作时,你应该使用[imageData bytes]和[imageData length]. NSData是一个obj-C类,它不是unsigned char数组.