Question

I need to parse the following string in Objective-C for iOS app

NSString *htmlString = @”12, 22, ‘stringA’,”, ‘stringB, stringC’, 2,’stringD'”;

I would like to an array like this

{
    @12,
    @22,
    @"stringA",
    @"emptySlotInfo",
    @"stringB, stringC",
    @2,
    @"stringD"
}

The headache is @”strinb, stringC” because

[htmlString componentsSeparatedByString:@","];

does not work for the case and the @”‘” as separator does not work either.

How can I get necessary components?

Answer 1

You could use NSScanner.

If it scans a ', it knows a string is starting and ignore ,till it reads the next '. if no opening ' was read, sperate by ,.

This cocoawithlove article might be helpful.

---

I made a quick prototype. Most likely there is much to optimize, as I am also not a expert for NSScanner

NSString *htmlString = @"12, 22, 'stringA','', 'stringB, stringC', 2,'stringD'";
NSScanner *scanner = [NSScanner scannerWithString:htmlString];

NSString *apostrophe = @"'";    // scanner needs to detect this
NSString *comma = @",";         // scanner needs to detect this
NSCharacterSet *charSet = [NSCharacterSet characterSetWithCharactersInString:[NSString stringWithFormat:@"%@%@", apostrophe, comma]];
BOOL apostropheOpen = NO;       // is the scan location inside a single quoted substring?
NSInteger lastCommaIndex = -1;  // track last found comma's index
NSMutableArray *array = [NSMutableArray array];

while (![scanner isAtEnd]) {
    [scanner scanUpToCharactersFromSet:charSet intoString:NULL];
    NSString *charAtlocation = [htmlString substringWithRange:NSMakeRange([scanner scanLocation], 1)];
    if ([charAtlocation isEqualToString:apostrophe]){
        apostropheOpen = !apostropheOpen;                
    } else if ([charAtlocation isEqualToString:comma]){
        if (!apostropheOpen) {
            [array addObject: [scanner.string substringWithRange:NSMakeRange(lastCommaIndex+1, [scanner scanLocation]- lastCommaIndex-1)]];
            lastCommaIndex = [scanner scanLocation];
        }
    }
    [scanner setScanLocation:[scanner scanLocation]+1];
} ;

// scanner only dealt with the string until the last comma, probably one more value to handle
if (lastCommaIndex < [scanner scanLocation]){
    [array addObject: [scanner.string substringWithRange:NSMakeRange(lastCommaIndex+1, [scanner scanLocation]- lastCommaIndex-1)]];
}

// array contains seperated strings, but with blanks and apostrophes
// we will deal with them now
__block NSMutableArray *resultArray = [NSMutableArray array];
[array enumerateObjectsUsingBlock:^(NSString *obj, NSUInteger idx, BOOL *stop) {
    obj = [[obj stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]
                stringByTrimmingCharactersInSet:charSet];
    if ([obj length] > 0)
        [resultArray addObject:obj];
    else
        [resultArray addObject:@"emptySlotInfo"];
}];

The resultArray contains

(
12,
22,
stringA,
emptySlotInfo,
stringB, stringC,
2,
stringD
)