Extracting price from string

Question

I am looking for a short and convenient way to extract a product's price from NSString. I have tried regular expressions, but always found some cases where did not match.

The price can be any number including decimals, 0 and -1 (valid prices: 10, 10.99, -1, 0).
NSString can contain a string like: @"Prod. price: $10.99"

Thanks!

You cannot cover 100% cases, don't even try to achieve that. — Andrey Gordeev, Nov 18 '13 at 12:17
It depends on ow well defined the surrounding context is. For example, is there always a preceding "$"? Is the price always at the end of the string? Provide full examples and the REs you have tried? Also have you tried `NSScanner`? — zaph, Nov 18 '13 at 12:20
No, but the numbers are always together. Maybe scan to the first number and then continue until I see a number and/or . ? — user-123, Nov 18 '13 at 12:21
I have tried (\\+|-)?([0-9]+(\\.[0-9]+)) and /^0$|^-?[1-9]\d*(\.\d+)?$/. both of them found on SO and they did not match all the cases above — user-123, Nov 18 '13 at 12:23
If you don't understand REs don't use them. Instead use `NSScanner`. `NSScanner` can be painful but it is straight forward. — zaph, Nov 18 '13 at 12:28

OGHaza · Accepted Answer · 2013-11-18T13:10:11.400

2

This will match all the examples you have given

-?\d+(\.\d{2})?

Optionally a -, followed by 1-many digits, optionally followed by a decimal point and 2 more digits.

If you've got other numbers that are not prices mixed in to the data then I don't think regex can fulfil your needs.

edited Nov 18 '13 at 13:10

answered Nov 18 '13 at 12:47

OGHaza

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If I want not only 2 numbers after decimal, then change it to: -?(\d+)(\.\d+)? ? – user-123 Nov 18 '13 at 13:00
Why two capture groups? `(-?\d+\.\d+)?` – zaph Nov 18 '13 at 13:02
@Zaph, you're right that the first group doesn't need to be captured (we're taking the whole match not any of the capture groups anyway) - will change that now. The 2nd group is in brackets because the `?` applies to only the `\.\d{2}`. - I could make it a non-capturing group, but like I said, we're ignoring the groups anyway. – OGHaza Nov 18 '13 at 13:09

score 2 · Answer 2 · answered Nov 18 '13 at 12:54

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NSString *originalString = @"Prod. price: $10.99";

NSScanner *scanner = [NSScanner scannerWithString:originalString];
NSCharacterSet *numbers = [NSCharacterSet characterSetWithCharactersInString:@"-0123456789"];

[scanner scanUpToCharactersFromSet:numbers intoString:NULL];
double number;
[scanner scanDouble:&number];

number is equal to 10.99

Obviously if you have other numbers before the value you looking for you wont find it.

answered Nov 18 '13 at 12:54

string.Empty

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Works, but a simpler solution is OGHaza's answer, using regex.. )) – user-123 Nov 18 '13 at 13:05

score 0 · Answer 3 · answered Nov 18 '13 at 13:02

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Assuming that your NSString will always contain the price with $ prep-ended to it, the following regex will match your need

.*?\$(-?(\d+)(.\d{1,2})?)

Once the above regex is matched you can find out match.group(1) to be the price from the NSString.

answered Nov 18 '13 at 13:02

Ramg

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No, $ is not obligatory – user-123 Nov 18 '13 at 13:04

Extracting price from string

3 Answers3

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