iphone - iOS - 使用 sqlite 数据库更新数据不起作用

Question

我想更新 Xcode sqlite 数据库中的一些数据。数据库连接成功，但是sql语句好像有问题，一直返回“添加联系人失败”，感谢帮助。

- (void) saveData:(id)sender
{

    NSLog(@"The code runs through here!");
    sqlite3_stmt    *statement;

    NSString *documents = [self applicationDocumentsDirectory];
    NSString *dbPath = [documents stringByAppendingPathComponent:@"monitorDB.sqlite"];
    const char *dbpath = [dbPath cStringUsingEncoding:NSASCIIStringEncoding];

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

        NSString *insertSQL = [NSString stringWithFormat:
                               @"UPDATE profile SET username = \"%@\" WHERE id = 1" ,
                               self.username.text];

        const char *insert_stmt = [insertSQL UTF8String];
        sqlite3_prepare_v2(contactDB, insert_stmt,
                           -1, &statement, NULL);
        if (sqlite3_step(statement) == SQLITE_DONE)
        {
            self.settingStatus.text = @"Contact added";
        } else {
            self.settingStatus.text = @"Failed to add contact";
        }
        sqlite3_finalize(statement);
        sqlite3_close(contactDB);
    }   else {
        self.settingStatus.text = @"DB Not Connect";
    }



}

Answer 1

尝试这样..

在viewdidload中我们需要检查表是否存在。如果没有，我们需要创建数据库。

NSString *docsdir;
NSArray *dirpaths;

dirpaths=NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsdir=[dirpaths objectAtIndex:0];
dabasePath=[NSString stringWithFormat:[docsdir stringByAppendingPathComponent:@"contact.db"]];

NSFileManager *filemgr= [NSFileManager defaultManager];
if ([filemgr fileExistsAtPath:dabasePath]==NO ) {
    const char *dbpath=[dabasePath UTF8String];
    if (sqlite3_open(dbpath, &contactDB)== SQLITE_OK) {
        char *error;
        const char *sql_stmt="CREATE TABLE IF NOT EXISTS CONTACTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, ADDRESS TEXT, NAME TEXT, PHONE TEXT, IMAGE BLOB)";
        if (sqlite3_exec(contactDB, sql_stmt, NULL, NULL, &error)!= SQLITE_OK) {
            status.text=@"failed to create";
        }
        sqlite3_close(contactDB);
    }
}

要保存数据，请尝试使用以下代码。

-(IBAction)saveData:(id)sender{

    sqlite3_stmt *statement;
    const char *dbpath = [dabasePath UTF8String];
    NSData *imagedata=UIImagePNGRepresentation(imageview.image);
    if (sqlite3_open(dbpath, &contactDB) == SQLITE_OK) {
        NSString *insertSql =[NSString stringWithFormat:@"INSERT INTO CONTACTS (name, address, phone, image) VALUES (\"%@\", \"%@\", \"%@\", ?) ", name.text, address.text, phone.text ];
        // NSString *nam=name.text;
        const char *insert_stmt = [insertSql UTF8String];
        sqlite3_prepare_v2(contactDB, insert_stmt, -1, &statement, NULL);
        sqlite3_bind_blob(statement, 1, [imagedata bytes], [imagedata length], NULL);

        if (sqlite3_step(statement) == SQLITE_DONE) {
          status.text=@"contact added";
          [self clearClick:nil];
        }else{
          status.text=@"failed to added";
        }
        sqlite3_finalize(statement);
        sqlite3_close(contactDB);
    }
}

要更新数据，请尝试使用以下代码。

-(IBAction)updateClick:(id)sender{

sqlite3_stmt *updateStmt;
 const char *dbpath = [dabasePath UTF8String];
if(sqlite3_open(dbpath, &contactDB) == SQLITE_OK)
{
    const char *sql = "update contacts Set address = ?, phone = ?, image = ? Where name=?";
    if(sqlite3_prepare_v2(contactDB, sql, -1, &updateStmt, NULL)==SQLITE_OK){
        sqlite3_bind_text(updateStmt, 4, [name.text UTF8String], -1, SQLITE_TRANSIENT);
        sqlite3_bind_text(updateStmt, 1, [address.text UTF8String], -1, SQLITE_TRANSIENT);
        sqlite3_bind_text(updateStmt, 2, [phone.text UTF8String], -1, SQLITE_TRANSIENT);
        NSData *imagedata=UIImagePNGRepresentation(imageview.image);
        sqlite3_bind_blob(updateStmt, 3, [imagedata bytes], [imagedata length], NULL);
    }
}
char* errmsg;
sqlite3_exec(contactDB, "COMMIT", NULL, NULL, &errmsg);

if(SQLITE_DONE != sqlite3_step(updateStmt)){
    NSLog(@"Error while updating. %s", sqlite3_errmsg(contactDB));
}
else{
    [self clearClick:nil];
}
sqlite3_finalize(updateStmt);
sqlite3_close(contactDB);
}