除了在 *.h 文件中的接口中声明之外，如何使从 NSManagedObject 子类化的对象的选择器对编译器可见？

Question

Core Data，NSManagedObject，

我从 MacResearch.org 获得了一个名为 Molecular Core 的演示应用程序的源代码，

其中有一个名为 Molecule 的类。它是 NSManagedObject 的子类。 当我尝试在 Molecule 实例上调用实例方法时 我在下面的 NSLog 消息后面收到“无法识别的选择器”错误消息：

2011-04-04 20:41:44.778 Molecular Core[13766:903] symbol=Ag 分子=（实体：分子；id：0x1230b70；数据：{ 原子 = ( ）； name = "新分子"; }) 坐标[1]=2.500000

---

2011-04-04 20:41:45.917 分子核心[13766:903] -[NSManagedObject addAtomWithPosition:andSymbol:]: 无法识别的选择器发送到实例 0x1234d00

---

这是我的问题：

Molecule.h 声明方法 - addAtomWithPosition:andSymbol: 与 Molecule.m 中的定义相同。 为什么系统找不到这个方法。分子的实例似乎仅被视为 其超类 NSManagedObject 的实例。这是为什么？

感谢您的阅读！ 标记

//
//  Molecule.h
//  Molecular Core
#import <Foundation/Foundation.h>
@class Atom;

@interface Molecule : NSManagedObject {
@private

}
@property (readwrite, copy) NSString *name;

/// THIS SELECTOR/METHOD IS 'INVISIBLE' TO COMPILER   //////

-(id)addAtomWithPosition:(double *)position andSymbol:(NSString *)symbol;

/// THIS CLASS METHOD IS VISIBLE TO COMPILER'   //////

+(id)moleculeFromXYZString:(NSString *)xyzString withName:(NSString *)name 
        inManagedObjectContext:(NSManagedObjectContext *)context;

@end
/// end molecule.h  /////////////////

// begin molecule.m  /////////////
//
//  Molecule.m

#import "Molecule.h"
#import "Atom.h"
#import "Element.h"

@implementation Molecule
@dynamic  name;


-(id)init
{
    self = [super init];
    if (self) {
        // Initialization code here.
    }

  return self;
}

    //// THIS CLASS METHOD RUNS     ////////////

    +(id)moleculeFromXYZString:(NSString *)xyzString 
       withName:(NSString *)name inManagedObjectContext:(NSManagedObjectContext *)context 
    {

   Molecule *molecule;

   molecule = (Molecule*) [NSEntityDescription insertNewObjectForEntityForName:@"Molecule" 
            inManagedObjectContext:context];

   molecule.name = name;

   NSScanner *scanner = [NSScanner scannerWithString:(nil == xyzString ? @"" : xyzString)];

   [scanner setCharactersToBeSkipped:[NSCharacterSet whitespaceCharacterSet]];

   BOOL xyzLine = NO;

   BOOL firstLineFound = NO;

   NSCharacterSet *newlineSet;

   newlineSet = [NSCharacterSet characterSetWithCharactersInString:@"\n"];

   while ( ![scanner isAtEnd] && ( ( xyzLine && firstLineFound ) || !firstLineFound ) ) 
    {

  NSString *line = nil;

  NSScanner *lineScanner;

  double coords[3];

  NSString *symbol;

  if ( ![scanner scanUpToCharactersFromSet:newlineSet intoString:&line] ) 
     line = @"";

  [scanner scanString:@"\n" intoString:NULL];

  lineScanner = [NSScanner scannerWithString:line]; // Create scanner for scanning line content

  [lineScanner setCharactersToBeSkipped:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

  xyzLine = [lineScanner scanCharactersFromSet:[NSCharacterSet letterCharacterSet] intoString:&symbol] &&
     [lineScanner scanDouble:&(coords[0])] && 
     [lineScanner scanDouble:&(coords[1])] && 
     [lineScanner scanDouble:&(coords[2])];

  NSLog(@"symbol=%@\nmolecule=%@\ncoords[1]=%f",symbol,molecule,(coords[1]));

  if ( xyzLine ) {

   firstLineFound = YES;

     //// THIS IS THE CALL THAT FAILS       /////////////////////

         [((Molecule*)molecule) addAtomWithPosition:(double *)coords andSymbol:(NSString*)symbol];
       }
     }

  return molecule;
  }

    -(id)addAtomWithPosition:(double *)position andSymbol:(NSString *)symbol {

       Atom *atom = [NSEntityDescription insertNewObjectForEntityForName:@"Atom" 
                                              inManagedObjectContext:[self managedObjectContext]];

       Element *element = [Element elementWithSymbol:symbol inManagedObjectContext:[self  managedObjectContext]];

       atom.molecule = self;

       atom.element = element;

       atom.positionX = [NSNumber numberWithDouble:position[0]];

       atom.positionY = [NSNumber numberWithDouble:position[1]];

       atom.positionZ = [NSNumber numberWithDouble:position[2]];

       NSLog(@"positionY=%@",atom.positionY);

       return atom;
    }


-(void)dealloc
{
  [super dealloc];
}

@end

Answer 1

NSManagedObject 不会响应选择器，但 NSManagedObject 的子类 Molecule 会响应。您需要将实体 Molecule 的类设置为 Core Data 模型中的类 Molecule。