Question

我正在尝试从数据库中选择数据，并且我有以下代码：代码：

// Setup the database object
 sqlite3 *database;

 // Init the animals Array
 list = [[NSMutableArray alloc] init];
 NSLog(@"documents path: ", documentsDir); 
 NSLog(@"database path: ", databasePath);

 // Open the database from the users filessytem
 if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) 
 {
  // Setup the SQL Statement and compile it for faster access
  const char *sqlStatement = "select route_name from Route";
  sqlite3_stmt *compiledStatement;
  if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) 
  {
   // Loop through the results and add them to the feeds array
   while(sqlite3_step(compiledStatement) == SQLITE_ROW) 
   {
    // Read the data from the result row
    NSString *aName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];

    // Add the animal object to the animals Array
    //[list addObject:animal];    
    [list addObject:aName];    
    //[animal release];
   }
  }
  // Release the compiled statement from memory
  sqlite3_finalize(compiledStatement);  
 }
 sqlite3_close(database);

我在第一个IF语句中收到EXC_BAD_ACCESS错误。任何人的想法。

同样在NSLOG documentsDir和databasePath中都是空白的。

我在ViewDidLoad中有以下代码：

-(void)viewDidLoad 
{ 
 // Setup some globals
 databaseName = @"xxxxxxCoreData.sqlite";

 // Get the path to the documents directory and append the databaseName
 NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
// NSString *documentsDir = [documentPaths objectAtIndex:0];
 documentsDir = [documentPaths objectAtIndex:0];
 databasePath = [documentsDir stringByAppendingPathComponent:databaseName];

Answer 1

看起来似乎没有保留databasePath，因此在运行视图和运行数据库代码之间，它已经被释放了。如果你想保留这些变量，你需要将最后两行更改为：

documentsDir = [[documentPaths objectAtIndex:0] retain];
databasePath = [[documentsDir stringByAppendingPathComponent:databaseName] retain];

由于您在viewDidLoad中执行此操作，因此您应该在viewDidUnload中释放它们（在此方法中也设置为nil）和dealloc。

SQLite问题 - 数据库路径

1 个答案: