How can I check whether a string contains the English Letters (A through Z) in Objective-C?
In PHP, there is preg_match method for that.
One approach would be to use regular expressions — the NSRegularExpression class. The following demonstrates how you could detect any English letters, but the pattern could be modified to match only if the entire string consists of such letters. Something like ^[a-zA-Z]*$.
NSRegularExpression *regex = [[[NSRegularExpression alloc]
initWithPattern:#"[a-zA-Z]" options:0 error:NULL] autorelease];
// Assuming you have some NSString `myString`.
NSUInteger matches = [regex numberOfMatchesInString:myString options:0
range:NSMakeRange(0, [myString length])];
if (matches > 0) {
// `myString` contains at least one English letter.
}
Alternatively, you could construct an NSCharacterSet containing the characters you're interested in and use NSString's rangeOfCharacterFromSet: to find the first occurrence of any one. I should note that this method only finds the first such character in the string. Maybe not what you're after.
Finally, I feel like you could do something with encodings, but haven't given this much thought. Perhaps determine if the string could be represented using ASCII (using canBeConvertedToEncoding:) and then check for numbers/symbols?
Oh, and you could always iterate over the string and check each character! :)
You can use simple NSPredicate test.
NSString *str = #"APPLE";
NSString *regex = #"[A-Z]+";
NSPredicate *test = [NSPredicate predicateWithFormat:#"SELF MATCHES %#", regex];
BOOL result = [test evaluateWithObject:str];
You could also use NSCharacterSet and use the rangeOfCharacterFromSet: method to see if the returned NSRange is the entire range of the string. characterSetWithRange would be a good place to start to create your characterSet.
You can use the NSRegularExpression Class (Apple's documentation on the class can be viewed here)
Related
I have a very big NSString, which holds around 1500 characters in it. In this string I need to extract a phone number, which may change frequently, as it is a dynamic data. The phone number will be in the format of 251-221-2000, how can I extract this?
Check out this previous question on regular expressions and NSString.
Search through NSString using Regular Expression
In your case an appropriate regular expression would be #"\\d{3}-\\d{3}-\\d{4}".
This sounds like a perfect candidate for a regular expression. You can use the NSRegularExpression class to achieve this. You can test your regular expression at http://www.regextester.com
NSString *yourString = #"Your 1500 characters string ";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression
regularExpressionWithPattern:#"\d{3}-\d{3}-\d{4}"
options:NSRegularExpressionCaseInsensitive
error:&error];
[regex enumerateMatchesInString:yourString options:0 range:NSMakeRange(0, [yourString length]) usingBlock:^(NSTextCheckingResult *match, NSMatchingFlags flags, BOOL *stop){
// your code to handle matches here
}];
Let me know it is working or not.
I have a string like:
<book>MyBook</book><value>myValue</value>
Now I want to get the text "myValue" out of this string. I want to use NSRegularExpression to do this. I tried this:
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"(<book>MyBook</book>\\s*<value>).*?(</value>)"
options:NSRegularExpressionCaseInsensitive
error:&error];
NSArray *textArray = [regex matchesInString:myData options:0 range:NSMakeRange(0, [myData length])];
NSTextCheckingResult * result = [rege firstMatchInString:myData
options:0
range:NSMakeRange(0, [myData length])];
The result is:
<book>MyBook</book><value>myValue</value>
So I get the whole string, but I only want "myValue". How can I do this? What am I missing here?
Thanks in advance!
That happens because you wrote a regex that matches the entire string. I'd reckon that writing a regex that will only match the myValue part of the string is way too complicated to be bothered with (due to the fact that you've got MyBook string that will probably match anything myValue does).
I'd recommend not using regex for this, as they are not intended for the use you've described here. If you don't want to use any XML deserialization, you could use a NSScanner or any of the NSString class methods which will yield a simpler, and easier code to maintain.
For example, using an NSScanner and a few other methods:
NSString *stringToBeScanned = #"<book>MyBook</book><value>myValue</value>";
NSString *myValue;
NSScanner *scanner = [NSScanner scannerWithString:stringToBeScanned];
[scanner scanUpToString:#"<value>" intoString:nil];
// After the above, we've got "<value>myValue</value>" left to scan
[scanner scanUpToString:#"</value>" intoString:&myValue];
// We ended up with a "<value>myValue" type of a string
// This will trim the remaining of the string we don't need
myValue = [myValue stringByReplacingOccurrencesOfString:#"<value>" withString:#""];
The above could probably be written better and I might have made a mistake or two writing it out my head, but the principle should work.
> (2009 RX7)</font></td>
>monospace" size="-1">214869 (2007 PAZ)</font></td>
>monospace" size="-1"> 4155 Accord</font></td>
I wonder if someone could offer me a little help, I have a list of NSString items (See Above) that I want to parse some data from. My problem is that there are no tags that I can use within the strings nor do the items I want have fixed positions. The data I want to extract is:
2009 RX7
2007 PAZ
4155 Accord
My thinking is that its going to be easier to parse from the right hand end, remove the </font></td> and then use ";" to separate the data items:
(2009  RX7)
(2007  PAZ)
4155  Accord
which can them be cleaned up to match the example given. Any pointers on doing this or working through from the right would be very much appreciated.
Personally I think you are better off with a regex. So my solution would be:
Regex of: ([0-9]+)[^;]+;([A-Za-z0-9]+)
Which for all the example text provides 3 matches. ie for:
(2009 RX7)</font></td>
0: 2009 RX7)<
1: 2009
2: RX7
I haven't coded this up, but did test the Regex at www.regextester.com
Regex's are implemented via NSRegularExpression and are available in iOS 4.0 and later.
Edit
Given that this appears to be a web scraping application, you never know when those pesky HTML code monkeys will change their output and break your carefully crafted matching methodology. As such I would change my regex to:
([0-9]+)([^;]+;)+([A-Za-z0-9]+)
Which adds an extra group, but allows for any number of elements between the number and the string.
Try this code:
NSString *str = #"> (2009 RX7)</font></td>";
NSRange fontRange = [str rangeOfString:#"</Font>" options:NSBackwardsSearch];
NSRange lastSemi = [str rangeOfString:#";" options:NSBackwardsSearch range:NSMakeRange(0, fontRange.location-1)];
NSRange priorSemi = [str rangeOfString:#";" options:NSBackwardsSearch range:NSMakeRange(0, lastSemi.location-1)];
NSString *yourString = [str substringWithRange:NSMakeRange(priorSemi.location+1, fontRange.location-1)];
The key element here is the NSBackwardsSearch search option.
This should do the trick:
NSString *s = #">monospace\" size=\"-1\"> 4155 Accord</font></td>";
NSArray *strArray = [s componentsSeparatedByString:#";"];
// you're interested in last two objects
NSArray *tmp = [strArray subarrayWithRange:NSMakeRange(strArray.count - 2, 2)];
In tmp you'll have something like:
"4155 ",
"Accord</font></td>"
strip unneeded chars and you're all set.
Using NSRegularExpression:
NSRegularExpression *regex;
NSTextCheckingResult *match;
NSString *pattern = #"([0-9]+) ([A-Za-z0-9]+)[)]?</font></td>";
NSString *string = #"> (2009 RX7)</font></td>";
regex = [NSRegularExpression
regularExpressionWithPattern:pattern
options:NSRegularExpressionCaseInsensitive
error:nil];
match = [regex firstMatchInString:string options:0 range:NSMakeRange(0, [string length])];
NSLog(#"'%#'", [string substringWithRange:[match rangeAtIndex:1]]);
NSLog(#"'%#'", [string substringWithRange:[match rangeAtIndex:2]]);
NSLog output:
'2009'
'RX7'
I want to replace all tags which are like <xxxx>.
I tried this:
- (NSString *)grabData:(NSString *)searchTerm {
// Setup an error to catch stuff in
NSError *error = NULL;
//Create the regular expression to match against
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"<.*>" options:NSRegularExpressionCaseInsensitive error:&error];
// create the new string by replacing the matching of the regex pattern with the template pattern(whitespace)
NSString *newSearchString = [regex stringByReplacingMatchesInString:searchTerm options:0 range:NSMakeRange(0, [searchTerm length]) withTemplate:#""];
NSLog(#"New string: %#",newSearchString);
return newSearchString;
}
But this just doesn't work. Could anyone help me?
The pattern <.*> matches a less-than, any amount of anything including a greater than, and then a greater-than. This pattern would, for instance, match a complete HTML file...
What you need is a <[^>]+> the [^>] is the set of all characters excluding greater-than, the + is "one or more", so the whole thing matches a less-than, one or more of anything excluding a greater than, and then a greater-than.
Your regular expression is incorrect.
< and > are meta characters and need escaping
The pattern matching should be .+
Based on this use
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"\\<.+\\>" options:NSRegularExpressionCaseInsensitive error:&error];
and it should work
I have the following code thats supposed to take the input entered into a UITextField and validate it. It doesn't seem to be working and Im a little confused as to why.
Could someone give me some advice please?
NSString *const regularExpression = #"([0-9a-zA-Z\\s]{1,6})";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:regularExpression options:NSRegularExpressionCaseInsensitive error:&error];
if (error)
{
NSLog(#"error %#", error);
}
NSUInteger numberOfMatches =
[regex numberOfMatchesInString:s options:0 range:NSMakeRange(0, [s length])];
NSLog(#"index = %d", i);
NSLog(#"Value of TextField = %#", s);
NSLog(#"Regular expression is = %#", regularExpression);
if (numberOfMatches <= 0)
{
NSLog(#"Failed regex test ");
}
This string should fail the regular expression test :"Einxnkxkd Xnckck"
But it passed.
im not sure how and why...
Anything obvious Im missing here?
Thanks
The method numberOfMatchesInString: searches for matches within the string. It does not test your pattern against the entire string.
It is passing because the pattern ([0-9a-zA-Z\\s]{1,6}) is matching at least the first six letters of your test string Einxnkxkd Xnckck yielding Einxnk. In fact, I can find lots of matches: E, Ein, inx, etc.
If you want to make sure the whole string matches the pattern, use ^ to indicate the beginning of the string and $ to mark the end of it, so that your pattern becomes ^([0-9a-zA-Z\\s]{1,6})$.
If you want to limit the expression to exactly the string, you need to wrap the expression in ^..$:
NSString *const regularExpression = #"^([0-9a-zA-Z\\s]{1,6})$";
Edit: Use the RegEx Air app to test, it's pretty handy (or any other reg exp tester)