objective-c - 使用Objective C解析SRT文件

文字范例:

1
00:00:00,000 --> 00:00:01,000
This is the first line

2
00:00:01,000 --> 00:00:02,000
This is the second line

3
00:00:02,000 --> 00:00:03,000
This is the last line

在JavaScript中，我肯定会用一个正则表达式来解析它。我只是想知道，这是在Obj C中执行此操作的最佳方法吗？我敢肯定我可以找到一种方法来做到这一点，但是我想以一种适当的方式来做到这一点。

我只需要知道从哪里开始，我很乐意做剩下的事情，但是为了理解起见，我将最终得到这样的东西(伪代码):

NSDictionary
index -> [0-9]+
start -> hh:mm:ss,mmm
end -> hh:mm:ss,mmm
text -> one of the lines of text

在这种情况下，我将在字典中解析三个条目。

最佳答案

背景知识:我编写了一个小应用程序，并创建了一个名为stuff.srt的文件，其中包含捆绑包中的示例。因此，我访问它的方式。

这只是一个快速而肮脏的事情，一个概念证明。请注意，它不会检查结果。实际的应用程序总是检查其结果。如您所见，工作是在-applicationDidFinishLaunching:方法中进行的(我在Mac OS X中工作，而不是iOS)。

编辑:

已经指出，最初发布的代码无法正确处理多行文本。为了解决这个问题，我利用了SRT files use CRLF as their line breaks这个事实，并搜索了该序列的两次出现。然后，根据观察到的here，将文本字符串中所有出现的CRLF更改为空格。这不考虑文本每一行中的前导或尾随空格。

我将stuff.srt文件的内容更改为此:

1
00:00:00,000 --> 00:00:01,000
This is the first line
and it has a secondary line

2
00:00:01,000 --> 00:00:02,000
This is the second line

3
00:00:02,000 --> 00:00:03,000
This is the last line
and it has a secondary line too

并且代码已作如下修改(我也将所有内容都放入了@autoreleasepool指令中；在解析文件的过程中可能会生成许多自动释放的对象!):

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
    NSString *path = [[NSBundle mainBundle] pathForResource:@"stuff" ofType:@"srt"];

    NSString *string = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:NULL];

    NSScanner *scanner = [NSScanner scannerWithString:string];

    while (![scanner isAtEnd])
    {
        @autoreleasepool
        {
            NSString *indexString;
            (void) [scanner scanUpToCharactersFromSet:[NSCharacterSet newlineCharacterSet] intoString:&indexString];

            NSString *startString;
            (void) [scanner scanUpToString:@" --> " intoString:&startString];

            // My string constant doesn't begin with spaces because scanners
            // skip spaces and newlines by default.
            (void) [scanner scanString:@"-->" intoString:NULL];

            NSString *endString;
            (void) [scanner scanUpToCharactersFromSet:[NSCharacterSet newlineCharacterSet] intoString:&endString];

            NSString *textString;
            // (void) [scanner scanUpToCharactersFromSet:[NSCharacterSet newlineCharacterSet] intoString:&textString];
            // BEGIN EDIT
            (void) [scanner scanUpToString:@"\r\n\r\n" intoString:&textString];
            textString = [textString stringByReplacingOccurrencesOfString:@"\r\n" withString:@" "];
            // Addresses trailing space added if CRLF is on a line by itself at the end of the SRT file
            textString = [textString stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
            // END EDIT

            NSDictionary *dictionary = [NSDictionary dictionaryWithObjectsAndKeys:
                                        indexString, @"index",
                                        startString, @"start",
                                        endString , @"end",
                                        textString , @"text",
                                        nil];

            NSLog(@"%@", dictionary);
        }
    }
}

修改后的输出如下所示:

2013-02-09 16:10:17.727 SRTFileScan[4846:303] {
    end = "00:00:01,000";
    index = 1;
    start = "00:00:00,000";
    text = "This is the first line and it has a secondary line";
}
2013-02-09 16:10:17.729 SRTFileScan[4846:303] {
    end = "00:00:02,000";
    index = 2;
    start = "00:00:01,000";
    text = "This is the second line";
}
2013-02-09 16:10:17.730 SRTFileScan[4846:303] {
    end = "00:00:03,000";
    index = 3;
    start = "00:00:02,000";
    text = "This is the last line and it has a secondary line too";
}

我从今天的阅读中学到的另一件事是:SRT文件格式起源于法国，输入中的逗号是在那里使用的十进制分隔符。