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在 iOS 编程方面，我是一个完全的新手，更不用说核心数据了。这对我来说相当不直观，因为我真正开始使用 MATLAB 进行编程，我猜它更像是一种“脚本”语言。

无论如何，我的问题是我不知道我必须做什么来为我的应用程序创建一个数据库。所以我读了一点，认为我必须为我的东西创建一个 SQL 数据库，然后导入它。长话短说，我创建了一个 SQLite 数据库，我想使用我已经完成的工作将内容导入我的 CoreData 数据库。

我尝试导出到以逗号分隔的文件和 xml 文件并读取它们，但我不喜欢它，这似乎是我不需要做的额外步骤。

因此，我将 SQLite 数据库导入到我的资源中并添加了 sqlite 框架。

我有我的核心数据模型设置，它正在后台为模型正确设置 SQLite 数据库。

当我运行我的程序将对象添加到我的实体时，它似乎可以工作，我什至可以在之后获取结果。但是，当我检查 Core Data Database SQLite 文件时，没有保存任何记录。

它怎么可能获取结果但不将它们保存到数据库中？

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{
//load in the path for resources
NSString *paths = [[NSBundle mainBundle] resourcePath];
NSString *databaseName = @"histology.sqlite";
NSString *databasePath = [paths stringByAppendingPathComponent:databaseName];
[self createDatabase:databasePath ];

NSError *error;
if ([[self managedObjectContext] save:&error]) {
    NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
}

// Test listing all CELLS from the store
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entityMO = [NSEntityDescription entityForName:@"CELL"
                                            inManagedObjectContext:[self managedObjectContext]];
[fetchRequest setEntity:entityMO];
NSArray *fetchedObjects = [[self managedObjectContext] executeFetchRequest:fetchRequest error:&error];
for (CELL *cellName in fetchedObjects) {
    //NSLog(@"cellName: %@", cellName);
}    


-(void) createDatabase:databasePath {
NSLog(@"The createDatabase function was entered.");  
NSLog(@"The databasePath is %@ ",[databasePath description]);
// Setup the database object
sqlite3 *histoDatabase;

// Open the database from filessytem
if(sqlite3_open([databasePath UTF8String], &histoDatabase) == SQLITE_OK) {
        NSLog(@"The database was opened");
    // Setup the SQL Statement and compile it for faster access
    const char *sqlStatement = "SELECT * FROM CELL";
    sqlite3_stmt *compiledStatement;

    if(sqlite3_prepare_v2(histoDatabase, sqlStatement, -1, &compiledStatement, NULL) != SQLITE_OK) {
        NSAssert1(0, @"Error while creating add statement. '%s'", sqlite3_errmsg(histoDatabase));
    }

    if(sqlite3_prepare_v2(histoDatabase, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) {

        // Loop through the results and add them to cell MO array
        while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
            CELL *cellMO = [NSEntityDescription insertNewObjectForEntityForName:@"CELL" inManagedObjectContext:[self managedObjectContext]];


            if (sqlite3_column_type(compiledStatement, 0) != SQLITE_NULL) {
                cellMO.cellName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 0)];
            } else {
                cellMO.cellName = @"undefined";
            }

            if (sqlite3_column_type(compiledStatement, 1) != SQLITE_NULL) {
                cellMO.cellDescription = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];
            } else {
                cellMO.cellDescription = @"undefined";
            }

                NSLog(@"The contents of NSString *cellName = %@",[cellMO.cellName   description]);

        }
    }


    // Release the compiled statement from memory
    sqlite3_finalize(compiledStatement);

}
sqlite3_close(histoDatabase);
}

我觉得这与打开/关闭两个数据库的时间有关？

附上我有一些SQL调试输出到终端

2012-05-28 16:03:39.556 MedPix[34751:fb03] The createDatabase function was entered.

2012-05-28 16:03:39.557 MedPix[34751:fb03] The databasePath is /Users/jack/Library/Application Support/iPhone Simulator/5.1/Applications/A6B2A79D-BA93-4E24-9291-5B7948A3CDF4/MedPix.app/histology.sqlite 

2012-05-28 16:03:39.559 MedPix[34751:fb03] The database was opened

2012-05-28 16:03:39.560 MedPix[34751:fb03] The database was prepared

2012-05-28 16:03:39.575 MedPix[34751:fb03] CoreData: annotation: Connecting to sqlite database file at "/Users/jack/Library/Application Support/iPhone Simulator/5.1/Applications/A6B2A79D-BA93-4E24-9291-5B7948A3CDF4/Documents/MedPix.sqlite"

2012-05-28 16:03:39.576 MedPix[34751:fb03] CoreData: annotation: creating schema.

2012-05-28 16:03:39.577 MedPix[34751:fb03] CoreData: sql: pragma page_size=4096

2012-05-28 16:03:39.578 MedPix[34751:fb03] CoreData: sql: pragma auto_vacuum=2

2012-05-28 16:03:39.630 MedPix[34751:fb03] CoreData: sql: BEGIN EXCLUSIVE

2012-05-28 16:03:39.631 MedPix[34751:fb03] CoreData: sql: SELECT TBL_NAME FROM SQLITE_MASTER WHERE TBL_NAME = 'Z_METADATA'

2012-05-28 16:03:39.632 MedPix[34751:fb03] CoreData: sql: CREATE TABLE ZCELL ( Z_PK INTEGER PRIMARY KEY, Z_ENT INTEGER, Z_OPT INTEGER, ZCELLDESCRIPTION VARCHAR, ZCELLNAME VARCHAR ) 
...

2012-05-28 16:03:39.669 MedPix[34751:fb03] CoreData: annotation: Creating primary key table.

2012-05-28 16:03:39.671 MedPix[34751:fb03] CoreData: sql: CREATE TABLE Z_PRIMARYKEY (Z_ENT INTEGER PRIMARY KEY, Z_NAME VARCHAR, Z_SUPER INTEGER, Z_MAX INTEGER)

2012-05-28 16:03:39.672 MedPix[34751:fb03] CoreData: sql: INSERT INTO Z_PRIMARYKEY(Z_ENT, Z_NAME, Z_SUPER, Z_MAX) VALUES(1, 'CELL', 0, 0)
...

2012-05-28 16:03:39.701 MedPix[34751:fb03] CoreData: sql: CREATE TABLE Z_METADATA (Z_VERSION INTEGER PRIMARY KEY, Z_UUID VARCHAR(255), Z_PLIST BLOB)

2012-05-28 16:03:39.702 MedPix[34751:fb03] CoreData: sql: SELECT TBL_NAME FROM SQLITE_MASTER WHERE TBL_NAME = 'Z_METADATA'

2012-05-28 16:03:39.703 MedPix[34751:fb03] CoreData: sql: DELETE FROM Z_METADATA WHERE Z_VERSION = ?

2012-05-28 16:03:39.704 MedPix[34751:fb03] CoreData: sql: INSERT INTO Z_METADATA (Z_VERSION, Z_UUID, Z_PLIST) VALUES (?, ?, ?)

2012-05-28 16:03:39.705 MedPix[34751:fb03] CoreData: sql: COMMIT

2012-05-28 16:03:39.710 MedPix[34751:fb03] CoreData: sql: pragma cache_size=200

2012-05-28 16:03:39.711 MedPix[34751:fb03] CoreData: sql: SELECT Z_VERSION, Z_UUID, Z_PLIST FROM Z_METADATA

2012-05-28 16:03:39.712 MedPix[34751:fb03] The contents of NSString *cellName = Beta Cell

2012-05-28 16:03:39.712 MedPix[34751:fb03] The contents of NSString *cellName = Gastric Chief Cell

...

2012-05-28 16:03:39.714 MedPix[34751:fb03] The database was prepared

2012-05-28 16:03:39.764 MedPix[34751:fb03] The createDatabase function has finished. Now fetching.

2012-05-28 16:03:39.765 MedPix[34751:fb03] CoreData: sql: SELECT 0, t0.Z_PK, t0.Z_OPT, t0.ZCELLDESCRIPTION, t0.ZCELLNAME FROM ZCELL t0 

2012-05-28 16:03:39.766 MedPix[34751:fb03] CoreData: annotation: sql connection fetch time: 0.0008s

2012-05-28 16:03:39.767 MedPix[34751:fb03] CoreData: annotation: total fetch execution time: 0.0016s for 0 rows.

2012-05-28 16:03:39.768 MedPix[34751:fb03] cellName: <CELL: 0x6bbc120> (entity: CELL; id: 0x6bbc160 <x-coredata:///CELL/t57D10DDD-74E2-474F-97EE-E3BD0FF684DA34> ; data: {
cellDescription = "S cells are cells which release secretin, found in the jejunum and duodenum. They are stimulated by a drop in pH to 4 or below in the small intestine's lumen. The released secretin will increase the s";
cellName = "S Cell";
organs =     (
);
specimens =     (
);
systems =     (
);
tissues =     (
);
})
...

部分被缩短以缩写。但请注意，提取结果包含信息，但它说总提取执行是针对“0”行？这个怎么可能？任何帮助将不胜感激，尤其是详细的解释。：） 谢谢。

4

2 回答 2

2

有几件事。

首先，根据您导入的数据库的大小，您可能希望从主线程中获取导入。否则，如果您在 applicationDidFinishLaunching: 方法中需要很长时间才能完成，系统将终止您的应用程序。您可以按如下方式执行此操作：

// If in applicationDidFinishLaunching, we need to first schedule on the main queue
// We do this to be one of the first things scheduled once the main queue starts running
dispatch_async(dispatch_get_main_queue(), ^{
    // now get off the main queue
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),^{
       [self createDatabase:databasePath];

       // Now put the results back on the main queue
       dispatch_async(dispatch_get_main_queue(), ^{
           NSError *error;
           if ([[self managedObjectContext] save:&error]) {
              NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
           }

       // Test listing all CELLS from the store
           NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
           NSEntityDescription *entityMO = [NSEntityDescription entityForName:@"CELL"
                                        inManagedObjectContext:[self managedObjectContext]];
           [fetchRequest setEntity:entityMO];
           NSArray *fetchedObjects = [[self managedObjectContext] executeFetchRequest:fetchRequest error:&error];
           for (CELL *cellName in fetchedObjects) {
              //NSLog(@"cellName: %@", cellName);
           }
       });    

    });
});

我会检查导入是否已完成，如果没有，则使用 Grand Central Dispatch 将导入工作从主线程中移除。

其次，正如 gerry3 在他的回答中提到的那样，您需要将 save: 消息发送到您的托管对象上下文。使用 iOS5 的父子上下文将允许您通过子上下文在后台轻松导入，然后将这些更改推送到主父上下文。查看 WWDC 2011 核心数据会话和堆栈溢出以获得良好的概述。

在您上面的代码的上下文中，您将执行以下所有操作：

// create a child context with a concurrent queue type.
NSManagedObjectContext *childManagedObjectContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];

// Set the parentContext.  Now whenever we save changes to the child context
// They will be pushed up to the parentContext and we can choose to save or throw them
// away
childManagedObjectContext.parentContext=self.managedObjectContext;

// Loop through the results and add them to cell MO array
NSInteger rowNumber=0;
while(sqlite3_step(compiledStatement) == SQLITE_ROW) {
        CELL *cellMO = [NSEntityDescription insertNewObjectForEntityForName:@"CELL" inManagedObjectContext:[self managedObjectContext]];


   if (sqlite3_column_type(compiledStatement, 0) != SQLITE_NULL) {
        cellMO.cellName = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 0)];
   } else {
        cellMO.cellName = @"undefined";
   }

   if (sqlite3_column_type(compiledStatement, 1) != SQLITE_NULL) {
        cellMO.cellDescription = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)];
   } else {
        cellMO.cellDescription = @"undefined";
   }
   NSLog(@"The contents of NSString *cellName = %@",[cellMO.cellName   description]);

   // Save our records periodically.  Choose a good number of iterations on this.
   // depends on your particular situation.
   if (rowNumber%100==0){
       NSError *mocError=nil;
       // Save the changes on the child context
       // This will push the changes up to the parent context.
       [childManagedObjectContext performBlock:^{
            [self.managedObjectContext save: &mocError];
            if (mocError){
                NSLog(@"mocError on rowNumber:  %d, error:  %@",rowNumber, error);
            }
            // Now save the changes on the parent context

            [self.managedObjectContext performBlock:^{
                    NSError *parentMocError=nil;
                    [self.managedObjectContext save: &parentMocError];
                    if (parentMocError){
                      NSLog(@"parentMocError on rowNumber:  %d, error:  %@",rowNumber, parentMocError);
                    }
             }];

       }];

   }
   rowNumber=rowNumber+1;
}

// Pickup and stragglers
[childManagedObjectContext performBlock:^{
     [self.managedObjectContext save: &mocError];
     if (mocError){
        NSLog(@"mocError on rowNumber:  %d, error:  %@",rowNumber, error);
     }
     // Now save the changes on the parent context

     [self.managedObjectContext performBlock:^{
           NSError *parentMocError=nil;
           [self.managedObjectContext save: &parentMocError];
               if (parentMocError){
                  NSLog(@"parentMocError on rowNumber:  %d, error:  %@",rowNumber, parentMocError);
               }
           }];

 }];

祝你好运！

蒂姆

于 2012-05-30T04:55:51.320 回答
0

插入所有新对象后，您需要再次save:使用。managedObjectContext

如果您要插入大量新对象，您可能希望在整个过程中定期保存。

于 2012-05-30T03:51:28.130 回答