Hi I'm looking to compare 2 strings using objective c. One string is a single word and the other will be one or more words. How can I cheeck for a match at word level? I.e if any word from the multiple word string matches my single word string return a 1 else return a 0 ? Any help much appreciated.
You might be tempted to use -[NSString rangeOfString:]:
if ([multipleWords rangeOfString:singleWord].location != NSNotFound)
return YES;
return NO;
But it's imperfect. You could have "returning" in multipleWords and singleWord could be "return", giving you a false positive.
So instead we must use NSRegularExpression.
NSString *single = #"returning";
NSString *multiple = #"a man is returning home";
NSString *pattern = [NSString stringWithFormat:#"\\b%#\\b",single];
NSError *error = nil;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern
options:NSRegularExpressionCaseInsensitive
error:&error];
NSRange range = NSMakeRange(0, multiple.length);
NSUInteger matched = [regex numberOfMatchesInString:multiple options:0 range:range];
NSLog(#"number of matched = %ld", matched);
You can use NSString's rangeOfString method:
NSRange range = [multiWordString rangeOfString:oneWordString];
if (range.location == NSNotFound)
return 0;
else
return 1;
The above code will return 1 if you are searching for "WAR" inside the longer "I AM AWARE". Maybe you're looking for entire word match.
In that case you should split the long string into an array of single words using...
NSArray *singleWords = [multiWordString componentsSeparatedByString: #" "];
Then parse the array to find the oneWordString
You can split up words in a string into an array using [string componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]. You can then check each word in the array to see if it matches the single word being searched. It's not the most efficient way, but it could work for your needs.
Related
How would I do this? I'm new to Objective-C but I can't find anything that would help me do this.
NSArray *splitLine = [currentLine componentsSeparatedByString:#":%#",notNumber];
Where notNumber is a string that represents anything that isn't a number. So I want to separate a string where there are colons separated by strings that aren't numbers. (I want to avoid splitting at times i.e. 3:00pm, but split at iCal parameters like DESCRIPTION: and LOCATION:.)
You can do this in several steps, like this. I have not compiled this code, but it should at least give you an idea of what to do.
1) Create a regex object to match your separators:
NSString *regexString = #"DESCRIPTION:\s|LOCATION:\s"; // or whatever makes sense for your scenario
NSRegularExpression *regex =
[NSRegularExpression regularExpressionWithPattern:regexString
options:NSRegularExpressionCaseInsensitive
error:nil];
2) Replace all the different separators matching your regex with just one separator:
NSRange range = NSMakeRange(0, string.length);
NSString *string2 = [regex stringByReplacingMatchesInString:string
options:0
range:range
withTemplate:#"SEPARATOR"];
3) Split the string!
NSArray *elements = [string2 componentsSeparatedByString:#"SEPARATOR"];
Shortest solution for splitting string.
NSString *str = #"Please split me to form array of words";
NSArray *wordsArray = [str componentsSeparatedByString:#" "];
You can use regular expressions!
Using the pattern (I believe this is the core of your question):
pattern = #"(?<=[^0-9]):(?=[^0-9])"
This pattern will only match ':' symbols not surrounded by numbers.
Then replace with a dummy value that won't show in your data
dummy = #"NEVERSEETHIS"
NSRegularExpressions *regex = [NSRegularExpression regularExpressionWithPattern:pattern options:0 error:nil];
NSRange range = NSMakeRange(0, [string length])
NSString *modified= [regex replaceMatchesInString:yourString options:0 range:range withTemplate:dummy];
and finally, split
return [modified componentsSeparatedByString:dummy];
Hi im trying to remove som HTML string from a web response. I want to remove <pre><a style="" name="output-line-1">1</a>, were the who instances of number "1"varies, but is always a digit. but how do i write the regex method for removing this? Below is what i have got so far:
-(NSString *)stringByStrippingHTML:(NSString*)str
{
NSRange r;
while ((r = [str rangeOfString:#"/^<pre><a style=\"\"name=\"output-line-([0-9])\">([0-9])</a>" options:NSRegularExpressionSearch]).location != NSNotFound){
str = [str stringByReplacingCharactersInRange:r withString:#""];
}
}
Basically I want to remove a substring with random number in it... In some instances of the substring the 1 is replaced, so that any similar string gets acknowledged, for example it could be output-line-999. How do i combine the range of string so i can both describe the string and specify to find any similar string with any number?
I want to remove both the HTML and the numbers.
This regular expression should work:
[str rangeOfString:#"<pre><a style=\"\" name=\"output-line-[0-9]+\">[0-9]+</a>" options:NSRegularExpressionSearch];
I thnk the problem is that there ins't a space before name in your reg expression
Using your original while loop, you can:
-(NSString *)stringByStrippingHTML:(NSString*)str
{
NSRange r;
while ((r = [str rangeOfString:#"<pre><a style=\"\" name=\"output-line-[0-9]+\">[0-9]+</a>" options:NSRegularExpressionSearch]).location != NSNotFound)
{
str = [str stringByReplacingCharactersInRange:r withString:#""];
}
}
Or you can use NSRegularExpression:
NSMutableString *input = ...
NSError *error;
NSRegularExpression *regex;
regex = [NSRegularExpression regularExpressionWithPattern:#"<pre><a style=\"\" name=\"output-line-[0-9]+\">[0-9]+</a>"
options:0
error:&error];
if (error)
{
NSLog(#"error=%#",error);
return;
}
[regex replaceMatchesInString:input
options:0
range:NSMakeRange(0, [input length])
withTemplate:#""];
As the title suggests, I would like to get the last word out of an NSString.
I thought using this code:
NSArray *listItems = [someNSStringHere componentsSeparatedByString:#" "];
NSString *lastWordString = [NSString stringWithFormat:#"%#", listItems.lastObject];
anotherNSStringHere = lastWordString;
But I think the NSArray will take a time to load if it's big (and it is big), and it wouldn't recognize a word separated by a comma.
Thanks for helping!
If you want to be super-robust:
__block NSString *lastWord = nil;
[someNSStringHere enumerateSubstringsInRange:NSMakeRange(0, [someNSStringHere length]) options:NSStringEnumerationByWords | NSStringEnumerationReverse usingBlock:^(NSString *substring, NSRange subrange, NSRange enclosingRange, BOOL *stop) {
lastWord = substring;
*stop = YES;
}];
(This should also work with non-Roman languages; iOS 4+/OS X 10.6+.)
Basic explanation:
-enumerateSubstringsInRage:options:usingBlock: does what it says on the tin: it enumerates substrings, which are defined by what you pass in as the options. NSStringEnumerationByWords says "I want words given to me", and NSStringEnumerationReverse says "start at the end of the string instead of the beginning".
Since we're starting from the end, the first word given to us in substring will be the last word in the string, so we set lastWord to that, and then set the BOOL pointed to by stop to YES, so the enumeration stops right away.
lastWord is of course defined as __block so we can set it inside the block and see it outside, and it's initialized to nil so if the string has no words (e.g., if it's empty or is all punctuation) we don't crash when we try to use lastWord.
Give this a try:
NSRange range = [someNSStringHere rangeOfString:#" " options:NSBackwardsSearch];
NSString *result = [someNSStringHere substringFromIndex:range.location+1];
If you wanted to use a regular expression (which can be useful if you want to start getting more complicated in terms of what you're looking for at the end of your string), you could do something like:
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:#"\\S+\\Z" options:0 error:nil];
NSTextCheckingResult *found = [regex firstMatchInString:inputString options:0 range:NSMakeRange(0, [inputString length])];
if (found.range.location != NSNotFound)
result = [inputString substringWithRange:found.range];
That works great as it also recognizes symbols like # and # which enumerateSubstringsInRange: doesn't do.
NSCharacterSet *charSet = [NSCharacterSet whitespaceAndNewlineCharacterSet];
NSArray *components = [someString componentsSeparatedByCharactersInSet:charSet];
NSString *lastWord = components.lastObject;
The most efficient way is likely to start at the end of the string, examine each character to see if it's part of what you define as a word, and then extract the word you want using substringFromIndex: or substringWithRange:.
You can read symbols from the end of the your string and copy them at the 0 index to result string. Whether you read space or comma, result string wil contain the last word
You could use NSString's function rangeOfSubstring:options: to determine it. For example:
Search the string for a space, using a backwards search option to start the search from the end of the string.
NSRange r = [string rangeOfString:#" " options:NSBackwardsSearch];
This will find the location of the last word of the string. Now just get the string using substringWithRange: For Example:
NSRange found = NSMakeRange(NSMaxRange(r), string.length - NSMaxRange(r));
NSString *foundString = [string substringWithRange:found];
Where r is the range from earlier.
Also be careful to make sure that you check r actually exists. If there is only 1 word in the string, then r will be {NSNotFound, 0}
Hope I could help!
Ben
I have a NSString category I am working on to perform character substitution similar to PHP's strtr. This method takes a string and replaces every occurrence of each character in fromString and replaces it with the character in toString with the same index. I have a working method but it is not very performant and would like to make it quicker and able to handle megabytes of data.
Edit (for clarity):
stringByReplacingOccurrencesOfString:withString:options:range: will not work. I have to take a string like "ABC" and after replacing "A" with "B" and "B" with "A" end up with "BAC". Successive invocations of stringByReplacingOccurrencesOfString:withString:options:range: would make a string like "AAC" which would be incorrect.
Suggestions would be great, sample code would be even better!
Code:
- (NSString *)stringBySubstitutingCharactersFromString:(NSString *)fromString
toString:(NSString *)toString;
{
NSMutableString *substitutedString = [self mutableCopy];
NSString *aCharacterString;
NSUInteger characterIndex
, stringLength = substitutedString.length;
for (NSUInteger i = 0; i < stringLength; ++i) {
aCharacterString = [NSString stringWithFormat: #"%C", [substitutedString characterAtIndex:i]];
characterIndex = [fromString rangeOfString:aCharacterString].location;
if (characterIndex == NSNotFound) continue;
[substitutedString replaceCharactersInRange:NSMakeRange(i, 1)
withString:[NSString stringWithFormat:#"%C", [toString characterAtIndex:characterIndex]]];
}
return substitutedString;
}
Also this code is executed after every change to text in a text view. It is passed the entire string every time. I know that there is a better way to do it, but I do not know how. Any suggestions for this would be most certainly appreciated!
You can make that kind of string substitution with NSRegularExpression either modifying an mutable string or creating a new immutable string. It will work with any two strings to substitute (even if they are more than one symbol) but you will need to escape any character that means something in a regular expression (like \ [ ( . * ? + etc).
The pattern finds either of the two substrings with the optional "anything" between and than replaces them with the two substrings with each other preserving the optional string between them.
// These string can be of any length
NSString *firstString = #"Axa";
NSString *secondString = #"By";
// Escaping of characters used in regular expressions has NOT been done here
NSString *pattern = [NSString stringWithFormat:#"(%#|%#)(.*?)(%#|%#)", firstString, secondString, firstString, secondString];
NSString *string = #"AxaByCAxaCBy";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:pattern
options:NSRegularExpressionCaseInsensitive
error:&error];
if (error) {
// Insert error handling here...
}
NSString *modifiedString = [regex stringByReplacingMatchesInString:string
options:0
range:NSMakeRange(0, [string length])
withTemplate:#"$3$2$1"];
NSLog(#"Before:\t%#", string); // AxaByCAxaCBy
NSLog(#"After: \t%#", modifiedString); // ByAxaCByCAxa
I'm trying to get the following regular expression to grab only the letters from an alpha-numeric character input box, however it's always returning the full string, and not any of the A-Z letters.
What am I doing wrong?
It needs to grab all the letters only. No weird characters and no numbers, just A-Z and put it into a string for me to use later on.
// A default follows
NSString *TAXCODE = txtTaxCode.text;
// Setup default for taxcode
if ([TAXCODE length] ==0)
{
TAXCODE = #"647L";
}
NSError *error = NULL;
NSRegularExpression *regex;
regex = [NSRegularExpression regularExpressionWithPattern:#"/[^A-Z]/gi"
options:NSRegularExpressionCaseInsensitive
error:&error];
NSLog(#"TAXCODE = %#", TAXCODE);
NSLog(#"TAXCODE.length = %d", [TAXCODE length]);
NSLog(#"STC (before regex) = %#", STC);
STC = [regex stringByReplacingMatchesInString:TAXCODE
options:0
range:NSMakeRange(0, [TAXCODE length])
withTemplate:#""];
NSLog(#"STC (after regex) = %#", STC);
My debug output is as follows:
TAXCODE = 647L
TAXCODE.length = 4
STC (before regex) =
STC (after regex) = 647L
If you only ever going to have letters on one end then you could use.
NSString *TAXCODE =#"647L";
NSString *newcode = [TAXCODE stringByTrimmingCharactersInSet:[NSCharacterSet decimalDigitCharacterSet]];
If intermixed letters then you can get an Array that you can then play with.
NSString *TAXCODE =#"L6J47L";
NSArray *newcodeArray = [TAXCODE componentsSeparatedByCharactersInSet:[NSCharacterSet decimalDigitCharacterSet]];
I think you need to drop the perl syntax on the regexp. Use #"[^A-Z]" as the match string.