使用 NSScanner 以逗号分隔字符串到 NSArray

Question

有谁知道我如何使用 NSScanner 将逗号分隔成一个数组，除非逗号嵌入引号中？

在我使用之前：

  NSArray *arrData = [strData componentsSeparatedByString:@","];

但是我在字符串中有引号，里面有逗号，我希望它们不要分开。我以前从未与 NSScanner 合作过，我正在努力接受文档。有没有人做过类似的事情？

Answer 1

如果你绝对必须使用 NSScanner，你可以这样做。

        NSScanner *scanner = [[NSScanner alloc] initWithString:@"\"Foo, Inc\",0.00,1.00,\"+1.5%\",\"+0.2%\",\"Foo"];
        NSCharacterSet *characters = [NSCharacterSet characterSetWithCharactersInString:@"\","];
        [scanner setCharactersToBeSkipped:nil];
        NSMutableArray *words = [[NSMutableArray alloc]init];
        NSMutableString *word = [[NSMutableString alloc] init];
        BOOL inQuotes = NO;
        while(scanner.isAtEnd == NO)
        {
            NSString *subString;
            [scanner scanUpToCharactersFromSet:characters intoString:&subString];
            NSUInteger currentLocation = [scanner scanLocation];
            if(currentLocation >= scanner.string.length)
            {
                if(subString.length > 0)
                    [words addObject:subString];
                break;
            }
            if([scanner.string characterAtIndex:currentLocation] == '"')
            {
                inQuotes = !inQuotes;
                if(subString == nil)
                {
                    [scanner setScanLocation:currentLocation + 1];
                    continue;
                }
                [word appendFormat:@"%@",subString];
                if(word.length > 0)
                   [words addObject:word.copy];
                [word deleteCharactersInRange:NSMakeRange(0, word.length)];
            }
            if([scanner.string characterAtIndex:currentLocation] == ',')
            {
                if(subString == nil)
                {
                    [scanner setScanLocation:currentLocation + 1];
                    continue;
                }
                if(inQuotes == NO)
                    [words addObject:subString];
                else
                    [word appendFormat:@"%@,",subString];
            }
            [scanner setScanLocation:currentLocation + 1];
        }

编辑： 这给出了以下输出：

Foo, Inc

0.00

1.00

+1.5%

+0.2%

富

希望这是你想要的

正如您所见，它变得复杂且非常容易出错，我建议为此使用正则表达式。

Answer 2

这与lead_the_zeppelin's answer 的一般程序相同，但我认为它要简单得多。我们使用NSMutableString、accum 来构建每个内部评论片段，其中可能包含任意数量的引用片段。

每次迭代，我们都会扫描到逗号、引号或字符串的结尾，以先到者为准。如果我们找到一个逗号，那么到目前为止积累的任何东西都应该被保存。对于引用，我们将所有内容提取到右引号 - 这是避免将引号内的逗号解释为分割点的关键。请注意，如果引号并不总是平衡的，这将不起作用。如果两者都不是，我们已经到了字符串的末尾，所以我们保存累积的字符串并退出。

// Demo data
NSArray * commaStrings = @[@"This, here, \"has\" no quoted, commas.",
                           @"This \"has, no\" unquoted \"commas,\"",
                           @"This, has,no,quotes",
                           @"This has no commas",
                           @"This has, \"a quoted\" \"phrase, followed\", by a, quoted phrase",
                           @"\"This\", one, \"went,\", to, \"mar,ket\"",
                           @"This has neither commas nor quotes",
                           @"This ends with a comma,"];

NSCharacterSet * commaQuoteSet = [NSCharacterSet characterSetWithCharactersInString:@",\""];

for( NSString * commaString in commaStrings ){

    NSScanner * scanner = [NSScanner scannerWithString:commaString];
    // Scanner ignores whitespace by default; turn that off.
    [scanner setCharactersToBeSkipped:nil];

    NSMutableArray * splitStrings = [NSMutableArray new];

    NSMutableString * accum = [NSMutableString new];

    while( YES ){

        // Set to an empty string for the case where the scanner is
        // at the end of the string and won't scan anything;
        // appendString: will die if its argument is nil.
        NSString * currScan = @"";
        // Scan up to a comma or a quote; this will go all the way to
        // the end of the string if neither of those exists.
        [scanner scanUpToCharactersFromSet:commaQuoteSet
                                intoString:&currScan];
        // Add the just-scanned material to whatever we've already got.
        [accum appendString:currScan];

        if( [scanner scanString:@"," intoString:NULL] ){
            // If it's a comma, save the accumulated string,
            [splitStrings addObject:accum];
            // clear it out,
            accum = [NSMutableString new];
            // and keep scanning.
            continue;
        }
        else if( [scanner scanString:@"\"" intoString:NULL] ) {
            // If a quote, append the quoted segment to the accumulation,
            [scanner scanUpToString:@"\""
                         intoString:&currScan];
            [accum appendFormat:@"\"%@\"", currScan];
            // and continue, appending until the next comma.
            [scanner scanString:@"\"" intoString:NULL];
            continue;
        }
        else {
            //Otherwise, there's nothing else to split; 
            // just save the remainder of the string
            [splitStrings addObject:accum];
            break;
        }

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

另外，as Chuck suggested，您可能只想获得一个 CSV 解析器。