获取"Undefined symbols for architecture i386:"尝试获取常量

Question

我知道有很多类似的问题，有点我没有找到我的情况：

我有：

#import <Foundation/Foundation.h>
@interface BSConstants : NSObject
extern NSString* const DB_COLUMN_NAME;
extern NSString* const DB_COLUMN_PRICE;
extern NSString* const DB_COLUMN_DESCRIPTION;
extern NSString* const DB_COLUMN_ICON;     
extern NSString* const DB_COLUMN_IMAGE; 
@end
#import "BSConstants.h"
@implementation BSConstants
NSString* const DB_COLUMN_NAME              = @"name";
NSString* const DB_COLUMN_PRICE             = @"price";
NSString* const DB_COLUMN_DESCRIPTION       = @"description";
NSString* const DB_COLUMN_ICON              = @"icon";
NSString* const DB_COLUMN_IMAGE             = @"image";
@end

当我尝试构建我的项目时，我得到：

Undefined symbols for architecture i386:
  "_CONST_SHOPPING_CART_PURCHASE_MAX_SIZE", referenced from:
      -[BSShoppingCartViewController onBuyButtonPressed:] in BSShoppingCartViewController.o
  "_NAME_CREATED_FILE", referenced from:
      -[BSImageSaver saveImageAsPng:] in BSImageSaver.o
  "_NAME_DOWNLOADS_FOLDER", referenced from:
      -[BSImageSaver saveImageAsPng:] in BSImageSaver.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

尝试访问：

#import "BSConstants.h"
 ... DB_COLUMN_NAME

Answer 1

我发现了错误 - 我在 .h 和 .m 文件中有不同的常量名称。

Answer 2

首先尝试更改此内容

extern NSString* const DB_COLUMN_NAME;到extern const NSString* DB_COLUMN_NAME;

与

NSString* const DB_COLUMN_NAME              = @"name";

自

const NSString* DB_COLUMN_NAME = @"name";

另请参阅您如何访问这些内容。