设置savepanel或openpanel的默认打开路径方法

NSSavePanel *fileDialog = [NSSavePanel savePanel];
[fileDialog setAllowedFileTypes:[NSArray arrayWithObject:@"rar"]];//允许保存的文件后缀名
[fileDialog setDirectoryURL:[NSURL fileURLWithPath:[NSHomeDirectory() stringByAppendingPathComponent:@"Desktop"]]];//设置默认打开路径
//        int result = [fileDialog runModalForDirectory:[NSHomeDirectory() stringByAppendingPathComponent:@"Desktop"] file:nil];       int result = [fileDialog runModal];
if (result == NSOKButton)
   self.file = [[fileDialog URL] path];//保存文件路径