How to write regex for Objective-C?

Question

I have some html data containing some img tags as follows:

img width=500 height=400
img width=400 height=250
img width=600 height=470

Height and width always changing. I have to replace that html data. I need to replace that html data to "img with=100" using Objective-C.

I wrote these but it's not matching

NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"/(img\\s)((width|height)(=)([0-9]+)"
                                                                       options:NSRegularExpressionCaseInsensitive
                                                                         error:&error];
NSUInteger numberOfMatches = [regex numberOfMatchesInString:myhtmldata
                                                    options:0
                                                      range:NSMakeRange(0, [myhtmldata length])];

NSString *modifiedString; 
if (numberOfMatches > 0)
{
   modifiedString = [regex stringByReplacingMatchesInString:myhtmldata
                                                           options:0
                                                             range:NSMakeRange(0, [myhtmldata length])
                                                      withTemplate:@"img width=30"];

}

Can you help me ?

Answer 1

If I infer the intent correctly from your sample code, you just want to use NSRegularExpression to change the width to 30. Then:

#import <Foundation/Foundation.h>

int main(int argc, char *argv[]) {
    @autoreleasepool {
        NSError *regexError = nil;
        NSRegularExpressionOptions options = 0;
        NSString *sampleText = @"img width=500 height=400";
        NSString *pattern = @"^(img\\s+)width=\\d+(\\s+height=\\d+)";
        NSRegularExpression *expression = [NSRegularExpression regularExpressionWithPattern:pattern options:options error:&regexError];

        sampleText = [expression stringByReplacingMatchesInString:sampleText
                                                          options:0
                                                            range:NSMakeRange(0,sampleText.length)
                                                     withTemplate:@"$1width=30$2"];
        printf("%s\n",[sampleText UTF8String]);
    }

}

prints img width=30 height=400 to the console.

EDIT:

You change change the regular expression to (img\\s+width=)\\d+\\s+height=\\d+ which when escaped properly will be:

@"(img\\s+width=)\\d+\\s+height=\\d+"

then change the template string to @"$130" . IF you make those changes to the my original code, you should match all occurrences of the img tag embedded in HTML. For example, it should change:

<html>
    <body>
        <img width=500 height=400>
        <img width=520 height=100>
    </body>
</html>

to:

<html>
    <body>
        <img width=30>
        <img width=30>
    </body>
</html>

Is this what your specs call for?

Answer 2

I found a different method and it's working. Here is code :

NSArray* ary = [oldHtml componentsSeparatedByString:@"<img"];
NSString* newHtml = [ary objectAtIndex:0];
for (int i = 1; i < [ary count]; i++) {

    newHtml = [newHtml stringByAppendingString:[@"<img width=300 " stringByAppendingString:[[ary objectAtIndex:i] substringFromIndex:[[ary objectAtIndex:i] rangeOfString:@"src"].location]]];

}

How to write regex for Objective-C?

Question

2 answers

solution1
2 2012-12-09 04:47:42

solution2
0 2012-12-09 23:14:37

How to write regex for Objective-C?

Question

2 answers

solution1 2 2012-12-09 04:47:42

solution2 0 2012-12-09 23:14:37

solution1
2 2012-12-09 04:47:42

solution2
0 2012-12-09 23:14:37