objective-c - hello world 中架构 x86_64 的 undefined symbol

Question

今天我正在学习 Objective-C，没有 Xcode，遵循这个 Guide

这是 Hello World :

ma​​kclass.m

#import "makclass.h"
#import <stdio.h>

@implementation MakClass

-(void) age {
    printf("Age is %d", age);
}

-(void) setAge: (int) a {
    age = a;
}

+(void) say {
    printf("Haha");
}
@end

ma​​kclass.h

#import <Foundation/NSObject.h>
@interface MakClass: NSObject {
    int age;
}

-(void) age;
-(void) setAge: (int) a;
+(void) say;
@end

helloworld.m

#import <stdio.h>
#import "makclass.h"
int main(void) {
    printf("Hello World");
    MakClass *makclass = [[MakClass alloc] init];
    [makclass setAge: 1];
    [makclass age];
    [MakClass say];
    [makclass release];
    return 0;
}

并且 clang helloworld.m 给我以下错误:

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_MakClass", referenced from:
      objc-class-ref in helloworld-XEijke.o
  "_objc_msgSend", referenced from:
      _main in helloworld-XEijke.o
  "_objc_msgSend_fixup", referenced from:
      l_objc_msgSend_fixup_alloc in helloworld-XEijke.o
      l_objc_msgSend_fixup_release in helloworld-XEijke.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Answer 1

您需要确保传递框架和所有文件:

clang -framework Foundation -o helloworld helloworld.m makclass.m