Modifying Occurrences of Time Format Regex in a Long String - ios

Question

I have strings containing Time values like 08:30:00AM and/or 12:45:00PM etc.
Now what i need is to remove the part containing 'seconds' value in these strings to make upper strings like 08:30AM and/or 12:45PM etc.
I can't use NSDateFormatter as it's not necessary that the string always contain time string in HH:MM:SS value.. There could be any string value else.. That's why I have to do it through patttern matching.
I know, i can use the following code. But what I need to know is what will be the regex to find and modify the string.
NSString *string = #"string containing 08:30:00AM values and some text";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"???" options:NSRegularExpressionCaseInsensitive error:&error];
NSString *modifiedString = [regex stringByReplacingMatchesInString:string options:0 range:NSMakeRange(0, [string length]) withTemplate:#""];
NSLog(#"%#", modifiedString);
Thanks in advance..

Answer 1

If it is time, then you can use dateformatter:
NSString *string = #"08:30:00AM"; //This is your input time
NSDateFormatter *df=[NSDateFormatter new];
[df setDateFormat:#"hh:mm:ssa"];
NSDate *nowTime=[df dateFromString:string];
[df setDateFormat:#"hh:mma"];
NSString *outputTime=[df stringFromDate:nowTime];
NSLog(#"time is : %#",outputTime);
Output: 08:30AM
EDIT:
Alternate way:
If you are sure your time is always in given format as 08:30:00AM and 08:30:05AM then you can use:
NSString *string = #"08:30:00AM";
NSString *aMPM=[string substringFromIndex:string.length-2];
NSString *noSecondAMPM= [string substringToIndex:string.length-5];
NSString *myTime=[NSString stringWithFormat: #"%#%#",noSecondAMPM,aMPM];
NSLog(#"time is : %#",myTime);

Answer 2

Just to give an answer along the lines of your own question, this regex pattern will match the time formats you are after and the parenthesis will capture the hour and minute part and allow you to keep them in the modified string:
NSString *timeText = #"This is a text with 08:30:23 and 9:23:54AM to test both formats.";
NSString *timePattern = #"([0-9]{1,2}:[0-9]{2}):[0-9]{2}";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:timePattern
options:0
error:&error];
NSString *modifiedString = [regex stringByReplacingMatchesInString:timeText
options:0
range:NSMakeRange(0, timeText.length)
withTemplate:#"$1"];
The result is this:
This is a text with 08:30 and 9:23AM to test both formats.
The $n (where n is a digit) in the replacement string refers to the nth capture group (parenthesis) in the regex pattern - in this case the hours, the colon and the minutes.
As you mentioned yourself, using regexes you can do the substitution directly in the text with no further parsing needed.
BTW, there are no letters in this pattern, so you don't need NSRegularExpressionCaseInsensitive.
This site is useful, e.g. the discussion on replacement strings and advanced syntax.