Question

我试图在viewDidLoad例程中打开一个sqlite db并尝试将sql查询发送到db，但sqlite_step（）每次都失败。我不确定这里有什么问题。我只是尝试将此作为sqlite3的hello world尝试。

#import "RootViewController.h"
#import "sqlite3.h"

static sqlite3_stmt *statement = nil;

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    NSString *dbname = @"name.sqlite";
    sqlite3 *database;
    int success;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:dbname];
    // Open the database. The database was prepared outside the application.
    success = sqlite3_open([path UTF8String], &database);
    if (success == SQLITE_OK) {
        NSLog(@"database opening successful : %d", success);
    } else {
        // Even though the open failed, call close to properly clean up resources.
        sqlite3_close(database);
        NSLog(@"database opening failed : %d", success);
        // Additional error handling, as appropriate...
    }
    if (statement == nil) {
        const char *sql = "insert into name(nid, name) values(6, 'testname');";
        success = sqlite3_prepare_v2(database, sql, -1, &statement, NULL);
        NSLog(@"query prepare status: %d", success);
        if (success != SQLITE_OK) {
        }
    }

    success = sqlite3_step(statement); //things fail here, as all calls above return ok
    NSLog(@"query step status: %d", success);
    if (success != SQLITE_DONE) {
    }
    sqlite3_reset(statement);
    sqlite3_close(database);
}
...

如果有人能指出我可能出错的地方，那就太好了。谢谢你的时间。

Answer 1

您是否确认该声明编译正常？您有success = sqlite3_prepare_v2(...);行，但如果success不是SQLITE_OK，则不会执行任何操作。您确认是SQLITE_OK吗？

另一方面，如果你使用像FMDB这样的包装器，你可以用以下代码替换上面的所有代码：

- (void)viewDidLoad {
    [super viewDidLoad];
    NSString *dbname = @"name.sqlite";
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:dbname];
    FMDatabase * database = [FMDatabase databaseWithPath:path];

    [database executeUpdate:@"insert into name(nid, name) values(?, ?)", [NSNumber numberWithInt:6], @"testname"];
    [database close];
}

这个，IMO，很多更容易调试。

Answer 2

我这样做但它仍然不起作用，因为在控制台中没有显示任何内容。

#import "RootViewController.h"
#import "FMDatabase.h"

@implementation RootViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    NSString *dbname = @"name.sqlite";
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *path = [documentsDirectory stringByAppendingPathComponent:dbname];
    FMDatabase * database = [FMDatabase databaseWithPath:path];
    FMResultSet *rs = [database executeQuery:@"select * from name;"];
    while ([rs next]) {
        NSLog(@"%d %@",
              [rs intForColumn:@"nid"],
              [rs stringForColumn:@"name"]);
    }
    [database close];
}
...

很抱歉，但我无法使用代码块，所以再次使用pre。

编辑：当我在FMDB中打开登录时，如下所示：

    FMDatabase * database = [FMDatabase databaseWithPath:path];

    [database setLogsErrors:YES];

    if (![database open]) { 
        NSLog(@"Could not open db."); 
    } else { 
        NSLog(@"DB Open...."); 
    }
    FMResultSet *rs = [database executeQuery:@"select * from 'name';"];
    while ([rs next]) {
        // just print out what we've got in a number of formats.
        NSLog(@"%d %@",
              [rs intForColumn:@"nid"],
              [rs stringForColumn:@"name"]);
    }
    [database close];

...，我在控制台中得到了这个：

[Session started at 2010-09-07 15:38:16 +0530.]
2010-09-07 15:38:19.178 MyDBTry[13670:207] DB Open....
2010-09-07 15:38:19.181 MyDBTry[13670:207] DB Error: 1 "no such table: name"
2010-09-07 15:38:19.182 MyDBTry[13670:207] DB Query: select * from name;

Sqlite3_step（）继续在此查询上返回SQLITE_MISUSE。有什么指针吗？

2 个答案: