objective-c - 对 '__objc_class_name_Fraction' 的 undefined reference

Question

我有这些文件:

Project.m

#import "Fraction.h"

int main(int argc, char *argv[]) {
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    Fraction *fraction = [[Fraction alloc] init];
    [fraction setNumerator: 2];
    [fraction setDenominator: 3];
    [fraction print];
    NSLog(@"%g", [fraction value]);
    [fraction release];
    [pool drain];
    return 0;
}

分数.m

#import "Fraction.h"

@implementation Fraction
-(void) setNumerator: (int) n {
    numerator = n;
}

-(void) setDenominator: (int) d {
    denominator = d;
}

-(void) print {
    NSLog(@"%i/%i\n", numerator, denominator);
}

-(double) value {
    return (double) numerator / denominator;
}
@end

分数.h

#import <Foundation/Foundation.h>

@interface Fraction: NSObject {
    int numerator, denominator;
}

-(void) setNumerator: (int) n;
-(void) setDenominator: (int) d;
-(void) print;
-(double) value;
@end

像这样安排在一个文件中:

Objective-C
|_Fraction.h
|_Fraction.m
|_Project.m

但是，当我运行它时(我正在使用 GNUstep)，我得到了这个错误:

undefined reference to '__objc_class_name_Fraction'

Answer 1

此错误告诉您 Fraction.m 未编译或链接，因此当您构建项目时，未找到 Fraction 类。

如果您忘记将 Fraction.m 添加到您的 GNUmakefile 中，就会出现此错误。

您可能有一个如下所示的 GNUmakefile:

include $(GNUSTEP_MAKEFILES)/common.make

TOOL_NAME = MyProject
MyProject_OBJC_FILES = Project.m

include $(GNUSTEP_MAKEFILES)/tool.make

您想将其更改为在 OBJC_FILES 行中包含 Fraction.m:

include $(GNUSTEP_MAKEFILES)/common.make

TOOL_NAME = MyProject
MyProject_OBJC_FILES = Project.m Fraction.m

include $(GNUSTEP_MAKEFILES)/tool.make

显然，您的 makefile 可能有所不同，但您明白了。确保在源文件列表中包含 Fraction.m。