iphone - 从 SQLite 读取 - FMDB - 初学者

Question

我正在尝试从数据库文件中读取(执行简单的选择所有功能)。

我正在使用 FMDB。

这是我创建数据库的方式；

Pro:~ dd$ sqlite3 db.db
SQLite version 3.7.7 2011-06-25 16:35:41
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> create table cus(id integer primary key, firstname varchar(30));
sqlite> inser into cus(firstname)values('f');
Error: near "inser": syntax error
sqlite> insert into cus(firstname)values('f');
sqlite> select * from cus;
1|f
sqlite> 

我将文件 (db.db) 复制到 xCode 中的资源文件夹中。在应用委托(delegate)中将 db 文件的名称更改为 db.db。我的程序的代码与 this tutorial. 完全相同

这是代码；

-(NSMutableArray *) getCustomers
{
    NSMutableArray *customers = [[NSMutableArray alloc] init];


    NSString * path = [(AppDelegate*)[[UIApplication sharedApplication]delegate]databasePath];
    NSLog(@"DB path %@ ",path);
    FMDatabase *db = [FMDatabase databaseWithPath:path];

    [db open];

    FMResultSet *results = [db executeQuery:@"SELECT * FROM cus"];
     NSLog(@"result %@ ",results);
    while([results next]) 
    {
        NSLog(@"result %@ ",results);
        Customer *customer = [[Customer alloc] init];

        customer.customerId = [results intForColumn:@"id"];
        customer.firstName = [results stringForColumn:@"firstname"];

        [customers addObject:customer];

    }

    [db close];

    return customers; 

}

我的问题;

尽管数据库中有 1 条记录， Select 的结果声明是 NULL .为什么会这样，我该如何纠正？

Answer 1

假设数据库已成功创建并导入到项目中，请尝试以下操作:

-(NSMutableArray *) getCustomers
{
 NSMutableArray *customers = [[NSMutableArray alloc] init];
 NSString * path = [(AppDelegate*)[[UIApplication sharedApplication]delegate]databasePath];
 NSLog(@"DB path %@ ",path);
 FMDatabase *db = [FMDatabase databaseWithPath:path];

 if(![db open])
 {
   NSLog(@"Could not open DB, try again");
   return nil;
 }

 FMResultSet *results = nil;
 results = [db executeQuery:@"SELECT * FROM cus"];
 NSLog(@"result %@ ",results);
 while([results next]) 
 {
   Customer *customer = [[Customer alloc] init];

   customer.customerId = [results intForColumn:@"id"];
   customer.firstName = [results stringForColumn:@"firstname"];

   NSLog(@"Customer object %@", customer);
   [customers addObject:customer];
   [customer release];
 }

 [db close];

 return customers; 
}