CODEWITHSUNDEEP
iosobjective-cstringnsstringsubstring
Želja Huber
Želja Huber

Reputation: 337

NSString Substring detection

I need help with replacing occurrences of string with another string. Occurrency that needs to be detected is actually some kind of function:

%nx+a or %nx-a

where x and a are some numbers.

So for example %n10+2 or %n54-11.

I can't even use something like:
NSRange startRange = [snippetString rangeOfString:@"%n"];

because if I have two patterns within same string I'm checking I'll only get starting range of first one...

Thanks.

Upvotes: 0

Views: 170

Answers (3)

SnakE
SnakE

Reputation: 2581

I assume that you need to do something with those two numbers. I think the best way is to use a regular expression to extract what you need in one go.

NSString * string = @"some %n5-3 string %n11+98";
NSError * regexError = nil;
NSRegularExpression * regex = [NSRegularExpression regularExpressionWithPattern:@"%n(\\d+)([+-])(\\d+)"
                                                                        options:0
                                                                          error:&regexError];
NSArray * matches = [regex matchesInString:string options:0 range:NSMakeRange(0, string.length)];
for (NSTextCheckingResult * match in matches) {
    NSString * firstNumber = [string substringWithRange:[match rangeAtIndex:1]];
    NSString * secondNumber = [string substringWithRange:[match rangeAtIndex:3]];
    NSString * sign = [string substringWithRange:[match rangeAtIndex:2]];
    // Do something useful with the numbers.
}

Of course if you just need to replace all the %n occurences with a constant string you can do that in one call:

NSString * result = [string stringByReplacingOccurrencesOfString:@"%n\\d+[+-]\\d+"
                                                      withString:@"here be dragons"
                                                         options:NSRegularExpressionSearch
                                                           range:NSMakeRange(0, string.length)];

Disclaimer: I didn't test this code. Minor bugs may be present.

Upvotes: 1

Mano
Mano

Reputation: 740

Alter this code to match ur need

yourString = [yourString stringByReplacingOccurrencesOfString:@" +" withString:@" "options:NSRegularExpressionSearch range:NSMakeRange(0, yourString.length)];

Upvotes: -1

Fogmeister
Fogmeister

Reputation: 77661

For something like this you could use an NSRegularExpression and use the method enumerateMatches:.

Or you can create your own loop.

The first is the easiest once you have the correct pattern.

Something like...

NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"%n" options:0 error:nil];

NSString *string = @"%n10+2*%n2";

[regex enumerateMatchesInString:string
options:0
range:NSMakeRange(0, string.length)
usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
    // here you will get each instance of a match to the pattern
}];

You will have to check the docs for NSRegularExpression to learn how to do what work you need to do with this.

Docs... https://developer.apple.com/library/mac/documentation/Foundation/Reference/NSRegularExpression_Class/Reference/Reference.html

Upvotes: 2

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