Question

我是Objective C的新手，在Windows上使用GNUstep。当我尝试编译以下代码时：

#import <Foundation/Foundation.h>
#import "song.h"

#define NSLog(FORMAT, ...) printf("%s\n", [[NSString stringWithFormat:FORMAT, ##__VA_ARGS__] UTF8String]);

int main (int argc, const char *argv[])
{

NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

//  Set up variables

//Read initial songs
NSError *error;
NSURL *playlistURL = [NSURL fileURLWithPath:@"C:\\ObjCPrograms\\PlayList\\playlist.txt"];
NSString *savedSongs = @"";
savedSongs = [[NSString alloc] initWithContentsOfURL:playlistURL encoding:NSUTF8StringEncoding error:&error];



//Separate initial songs into array
NSMutableArray *savedSongsArray;
NSMutableArray *songLine = (NSMutableArray *)[savedSongs componentsSeparatedByString:@"\n"];
int line = 0;



for(line; line < [songLine count]; line++)
{
    NSMutableArray *lineContents = (NSMutableArray *)[[songLine objectAtIndex:line] componentsSeparatedByString:@"|"];
    song *newSong = [[song alloc]init];
    [song autorelease];

    NSString *title = [lineContents objectAtIndex:0];
    NSString *performer = [lineContents objectAtIndex:1];
    NSString *genre = [lineContents objectAtIndex:2];
    NSString *length = [lineContents objectAtIndex:3];

    NSLog(@"%@|%@|%@|%@", title, performer, genre, length);

    [newSong setTitle: title];

    NSLog(@"here");

    [newSong setPerformer: performer];
    [newSong setGenre: genre];
    [newSong setLength: length];

    [savedSongsArray addObject:newSong];
}

使用命令

gcc -o PlayList playList.m -I/c/GNUstep/GNUstep/System/Library/Headers \
-L /c/GNUstep/GNUstep/System/Library/Libraries -lobjc -lgnustep-base \
-fconstant-string-class=NSConstantString

我收到错误消息

playList.m:(.data+0x230): undefined reference to `__objc_class_name_song'
collect2: ld returned 1 exit status

我相信我的问题是newsong的声明，因为当我用

替换它时

song *newSong;

我的代码编译。但是，当我运行此代码时，程序在我调用newSong的setter时崩溃了：

[newSong setTitle: title];

我检查了，甚至从未调用过setter。根据我的阅读，链接可能存在问题，但我找不到任何拼写错误或丢失代码。

这是我在界面和歌曲实现中的setter方法：

- (void) setTitle: (NSString *) newTitle;

- (void) setTitle: (NSString *) newTitle;
{
    [newTitle retain];
    [title release];
    title = newTitle;
}

声明变量会导致“未定义的引用”错误消息

0 个答案: