Question

我正在尝试创建一个SQLite数据库，但遇到的问题似乎是从表中从未创建的CONTACTS（我收到错误消息'插入时出错'没有这样的表：CONTACTS' “）。

从下面的代码中，任何人都可以看到错误以及如何纠正错误？这个例子直接来自本指南，这就是为什么我感到惊讶它不起作用： http://www.techotopia.com/index.php/An_Example_SQLite_based_iOS_6_iPhone_Application

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

    // Get the documents directory

    dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    docsDir = dirPaths[0];

    //Buid the path for database file
    _databasePath = [[NSString alloc]
                     initWithString:[docsDir stringByAppendingPathComponent:@"contacts.db"]];

    NSFileManager *filemgr = [NSFileManager defaultManager];

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

        if(sqlite3_open(db_path, &_contactDB) == SQLITE_OK)
        {
            char *errMsg;

            const char *sql_stmt =
            "CREATE TABLE IF NOT EXISTS CONTACTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT)";

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

}

- (IBAction)saveName:(id)sender {


NSString *currentName = self.text.text;
NSString *nameSaved = [[NSString alloc] initWithFormat:currentName];


    sqlite3_stmt    *statement;
    const char *dbpath = [_databasePath UTF8String];

    if (sqlite3_open(dbpath, &_contactDB) == SQLITE_OK)
    {
        NSLog(@"pass");
        NSString *insertSQL = [NSString stringWithFormat:
                               @"INSERT INTO CONTACTS (name) VALUES (\"%@\")",
                               nameSaved];

        const char *insert_stmt = [insertSQL UTF8String];
        sqlite3_prepare_v2(_contactDB, insert_stmt,
                           -1, &statement, NULL);
        if (sqlite3_step(statement) == SQLITE_DONE)
        {
        NSLog(@"pass");
        } else {
        NSLog( @"Error while inserting '%s'", sqlite3_errmsg(_contactDB));
        }
        sqlite3_finalize(statement);
        sqlite3_close(_contactDB);

    }  
}

Answer 1

使用objectAtIndex：

sqlite3*    _contactDB;
NSString *docsDir;
NSArray *dirPaths;

// Get the documents directory

dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
docsDir = [dirPaths objectAtIndex:0];

//Buid the path for database file
  NSString *  _databasePath = [[NSString alloc]
                     initWithString:[docsDir stringByAppendingPathComponent:@"contacts.db"]];

NSFileManager *filemgr = [NSFileManager defaultManager];

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

    if(sqlite3_open(db_path, &_contactDB) == SQLITE_OK)
    {
        char *errMsg;

        const char *sql_stmt =
        "CREATE TABLE IF NOT EXISTS CONTACTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT)";

        if (sqlite3_exec(_contactDB, sql_stmt, NULL, NULL, &errMsg) != SQLITE_OK)
        {
            NSLog(@"Failed to create table") ;
        }
        sqlite3_close(_contactDB);
    } else { 
       NSLog( @"Failed to open/create database");
    }
}

Answer 2

该代码没有任何问题 - 它可以在Mac OS X和iOS模拟器中正常运行。当您尝试将数据插入表中时，错误是否会出现？在尝试向其中插入数据之前，您是在关闭文件吗？

在模拟器中运行它，逐步执行代码，然后在模拟器的Documents目录中找到该文件。使用终端查看文件中的内容：

sqlite3 path-to-file .dump

您的计算机上的确切路径会有所不同，但在我的iOS模拟器中，我得到：

sqlite3 "/Users/my-login-name/Library/Application Support/iPhone Simulator/6.1/Applications/DAD0BB47-2136-4367-8DAF-AA578D0C00A5/Documents/contacts.db" .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE CONTACTS (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT);
COMMIT;

您可以看到该表存在正确的列。

SQLite数据库表从未创建过

2 个答案: