//遍历~目录下，后缀名为jpg的文件的，然后打印"路径/文件"        NSFileManager *manger;        manger = [NSFileManager defaultManager]; //singleton instance                NSString *home;                           //home path        home = [@"~" stringByExpandingTildeInPath]; //use home path instead of ~ by the method                NSDirectoryEnumerator *direnum;        direnum = [manger enumeratorAtPath:home]; //all of the file path                NSMutableArray *files;        files = [NSMutableArray arrayWithCapacity:42];                NSString *filename;        while (filename = [direnum nextObject]) {            if ([[filename pathExtension] isEqualToString:@"jpg"]) { //pathExtension: file extension                [files addObject:filename];            }        }                NSEnumerator *fileenum;        fileenum = [files objectEnumerator]; //迭代器，类似于C++中的iterator                while (filename = [fileenum nextObject]) {            NSLog(@"%@", filename);        }