NSString tokenize in Objective-C - objective-c

Question

What is the best way to tokenize/split a NSString in Objective-C?

Answer 1

Found answer here:
NSString *string = #"oop:ack:bork:greeble:ponies";
NSArray *chunks = [string componentsSeparatedByString: #":"];

Answer 2

Everyone has mentioned componentsSeparatedByString: but you can also use CFStringTokenizer (remember that an NSString and CFString are interchangeable) which will tokenize natural languages too (like Chinese/Japanese which don't split words on spaces).

Answer 3

If you just want to split a string, use -[NSString componentsSeparatedByString:]. For more complex tokenization, use the NSScanner class.

Answer 4

If your tokenization needs are more complex, check out my open source Cocoa String tokenizing/parsing toolkit: ParseKit:
http://parsekit.com
For simple splitting of strings using a delimiter char (like ':'), ParseKit would definitely be overkill. But again, for complex tokenization needs, ParseKit is extremely powerful/flexible.
Also see the ParseKit Tokenization documentation.

Answer 5

If you want to tokenize on multiple characters, you can use NSString's componentsSeparatedByCharactersInSet. NSCharacterSet has some handy pre-made sets like the whitespaceCharacterSet and the illegalCharacterSet. And it has initializers for Unicode ranges.
You can also combine character sets and use them to tokenize, like this:
// Tokenize sSourceEntityName on both whitespace and punctuation.
NSMutableCharacterSet *mcharsetWhitePunc = [[NSCharacterSet whitespaceAndNewlineCharacterSet] mutableCopy];
[mcharsetWhitePunc formUnionWithCharacterSet:[NSCharacterSet punctuationCharacterSet]];
NSArray *sarrTokenizedName = [self.sSourceEntityName componentsSeparatedByCharactersInSet:mcharsetWhitePunc];
[mcharsetWhitePunc release];
Be aware that componentsSeparatedByCharactersInSet will produce blank strings if it encounters more than one member of the charSet in a row, so you might want to test for lengths less than 1.

Answer 6

If you're looking to tokenise a string into search terms while preserving "quoted phrases", here's an NSString category that respects various types of quote pairs: "" '' ‘’ “”
Usage:
NSArray *terms = [#"This is my \"search phrase\" I want to split" searchTerms];
// results in: ["This", "is", "my", "search phrase", "I", "want", "to", "split"]
Code:
#interface NSString (Search)
- (NSArray *)searchTerms;
#end
#implementation NSString (Search)
- (NSArray *)searchTerms {
// Strip whitespace and setup scanner
NSCharacterSet *whitespace = [NSCharacterSet whitespaceAndNewlineCharacterSet];
NSString *searchString = [self stringByTrimmingCharactersInSet:whitespace];
NSScanner *scanner = [NSScanner scannerWithString:searchString];
[scanner setCharactersToBeSkipped:nil]; // we'll handle whitespace ourselves
// A few types of quote pairs to check
NSDictionary *quotePairs = #{#"\"": #"\"",
#"'": #"'",
#"\u2018": #"\u2019",
#"\u201C": #"\u201D"};
// Scan
NSMutableArray *results = [[NSMutableArray alloc] init];
NSString *substring = nil;
while (scanner.scanLocation < searchString.length) {
// Check for quote at beginning of string
unichar unicharacter = [self characterAtIndex:scanner.scanLocation];
NSString *startQuote = [NSString stringWithFormat:#"%C", unicharacter];
NSString *endQuote = [quotePairs objectForKey:startQuote];
if (endQuote != nil) { // if it's a valid start quote we'll have an end quote
// Scan quoted phrase into substring (skipping start & end quotes)
[scanner scanString:startQuote intoString:nil];
[scanner scanUpToString:endQuote intoString:&substring];
[scanner scanString:endQuote intoString:nil];
} else {
// Single word that is non-quoted
[scanner scanUpToCharactersFromSet:whitespace intoString:&substring];
}
// Process and add the substring to results
if (substring) {
substring = [substring stringByTrimmingCharactersInSet:whitespace];
if (substring.length) [results addObject:substring];
}
// Skip to next word
[scanner scanCharactersFromSet:whitespace intoString:nil];
}
// Return non-mutable array
return results.copy;
}
#end

Answer 7

If you are looking for splitting linguistic feature's of a string (Words, paragraphs, characters, sentences and lines), use string enumeration:
NSString * string = #" \n word1! word2,%$?'/word3.word4 ";
[string enumerateSubstringsInRange:NSMakeRange(0, string.length)
options:NSStringEnumerationByWords
usingBlock:
^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
NSLog(#"Substring: '%#'", substring);
}];
// Logs:
// Substring: 'word1'
// Substring: 'word2'
// Substring: 'word3'
// Substring: 'word4'
This api works with other languages where spaces are not always the delimiter (e.g. Japanese). Also using NSStringEnumerationByComposedCharacterSequences is the proper way to enumerate over characters, since many non-western characters are more than one byte long.

Answer 8

I had a case where I had to split the console output after an LDAP query with ldapsearch. First set up and execute the NSTask (I found a good code sample here: Execute a terminal command from a Cocoa app). But then I had to split and parse the output so as to extract only the print-server names out of the Ldap-query-output. Unfortunately it is rather tedious string-manipulation which would be no problem at all if we were to manipulate C-strings/arrays with simple C-array operations. So here is my code using cocoa objects. If you have better suggestions, let me know.
//as the ldap query has to be done when the user selects one of our Active Directory Domains
//(an according comboBox should be populated with print-server names we discover from AD)
//my code is placed in the onSelectDomain event code
//the following variables are declared in the interface .h file as globals
#protected NSArray* aDomains;//domain combo list array
#protected NSMutableArray* aPrinters;//printer combo list array
#protected NSMutableArray* aPrintServers;//print server combo list array
#protected NSString* sLdapQueryCommand;//for LDAP Queries
#protected NSArray* aLdapQueryArgs;
#protected NSTask* tskLdapTask;
#protected NSPipe* pipeLdapTask;
#protected NSFileHandle* fhLdapTask;
#protected NSMutableData* mdLdapTask;
IBOutlet NSComboBox* comboDomain;
IBOutlet NSComboBox* comboPrinter;
IBOutlet NSComboBox* comboPrintServer;
//end of interface globals
//after collecting the print-server names they are displayed in an according drop-down comboBox
//as soon as the user selects one of the print-servers, we should start a new query to find all the
//print-queues on that server and display them in the comboPrinter drop-down list
//to find the shares/print queues of a windows print-server you need samba and the net -S command like this:
// net -S yourPrintServerName.yourBaseDomain.com -U yourLdapUser%yourLdapUserPassWord -W adm rpc share -l
//which dispalays a long list of the shares
- (IBAction)onSelectDomain:(id)sender
{
static int indexOfLastItem = 0; //unfortunately we need to compare this because we are called also if the selection did not change!
if ([comboDomain indexOfSelectedItem] != indexOfLastItem && ([comboDomain indexOfSelectedItem] != 0))
{
indexOfLastItem = [comboDomain indexOfSelectedItem]; //retain this index for next call
//the print-servers-list has to be loaded on a per univeristy or domain basis from a file dynamically or from AN LDAP-QUERY
//initialize an LDAP-Query-Task or console-command like this one with console output
/*
ldapsearch -LLL -s sub -D "cn=yourLdapUser,ou=yourOuWithLdapUserAccount,dc=yourDomain,dc=com" -h "yourLdapServer.com" -p 3268 -w "yourLdapUserPassWord" -b "dc=yourBaseDomainToSearchIn,dc=com" "(&(objectcategory=computer)(cn=ps*))" "dn"
//our print-server names start with ps* and we want the dn as result, wich comes like this:
dn: CN=PSyourPrintServerName,CN=Computers,DC=yourBaseDomainToSearchIn,DC=com
*/
sLdapQueryCommand = [[NSString alloc] initWithString: #"/usr/bin/ldapsearch"];
if ([[comboDomain stringValue] compare: #"firstDomain"] == NSOrderedSame) {
aLdapQueryArgs = [NSArray arrayWithObjects: #"-LLL",#"-s", #"sub",#"-D", #"cn=yourLdapUser,ou=yourOuWithLdapUserAccount,dc=yourDomain,dc=com",#"-h", #"yourLdapServer.com",#"-p",#"3268",#"-w",#"yourLdapUserPassWord",#"-b",#"dc=yourFirstDomainToSearchIn,dc=com",#"(&(objectcategory=computer)(cn=ps*))",#"dn",nil];
}
else {
aLdapQueryArgs = [NSArray arrayWithObjects: #"-LLL",#"-s", #"sub",#"-D", #"cn=yourLdapUser,ou=yourOuWithLdapUserAccount,dc=yourDomain,dc=com",#"-h", #"yourLdapServer.com",#"-p",#"3268",#"-w",#"yourLdapUserPassWord",#"-b",#"dc=yourSecondDomainToSearchIn,dc=com",#"(&(objectcategory=computer)(cn=ps*))",#"dn",nil];
}
//prepare and execute ldap-query task
tskLdapTask = [[NSTask alloc] init];
pipeLdapTask = [[NSPipe alloc] init];//instead of [NSPipe pipe]
[tskLdapTask setStandardOutput: pipeLdapTask];//hope to get the tasks output in this file/pipe
//The magic line that keeps your log where it belongs, has to do with NSLog (see https://stackoverflow.com/questions/412562/execute-a-terminal-command-from-a-cocoa-app and here http://www.cocoadev.com/index.pl?NSTask )
[tskLdapTask setStandardInput:[NSPipe pipe]];
//fhLdapTask = [[NSFileHandle alloc] init];//would be redundand here, next line seems to do the trick also
fhLdapTask = [pipeLdapTask fileHandleForReading];
mdLdapTask = [NSMutableData dataWithCapacity:512];//prepare capturing the pipe buffer which is flushed on read and can overflow, start with 512 Bytes but it is mutable, so grows dynamically later
[tskLdapTask setLaunchPath: sLdapQueryCommand];
[tskLdapTask setArguments: aLdapQueryArgs];
#ifdef bDoDebug
NSLog (#"sLdapQueryCommand: %#\n", sLdapQueryCommand);
NSLog (#"aLdapQueryArgs: %#\n", aLdapQueryArgs );
NSLog (#"tskLdapTask: %#\n", [tskLdapTask arguments]);
#endif
[tskLdapTask launch];
while ([tskLdapTask isRunning]) {
[mdLdapTask appendData: [fhLdapTask readDataToEndOfFile]];
}
[tskLdapTask waitUntilExit];//might be redundant here.
[mdLdapTask appendData: [fhLdapTask readDataToEndOfFile]];//add another read for safety after process/command stops
NSString* sLdapOutput = [[NSString alloc] initWithData: mdLdapTask encoding: NSUTF8StringEncoding];//convert output to something readable, as NSData and NSMutableData are mere byte buffers
#ifdef bDoDebug
NSLog(#"LdapQueryOutput: %#\n", sLdapOutput);
#endif
//Ok now we have the printservers from Active Directory, lets parse the output and show the list to the user in its combo box
//output is formatted as this, one printserver per line
//dn: CN=PSyourPrintServer,OU=Computers,DC=yourBaseDomainToSearchIn,DC=com
//so we have to search for "dn: CN=" to retrieve each printserver's name
//unfortunately splitting this up will give us a first line containing only "" empty string, which we can replace with the word "choose"
//appearing as first entry in the comboBox
aPrintServers = (NSMutableArray*)[sLdapOutput componentsSeparatedByString:#"dn: CN="];//split output into single lines and store it in the NSMutableArray aPrintServers
#ifdef bDoDebug
NSLog(#"aPrintServers: %#\n", aPrintServers);
#endif
if ([[aPrintServers objectAtIndex: 0 ] compare: #"" options: NSLiteralSearch] == NSOrderedSame){
[aPrintServers replaceObjectAtIndex: 0 withObject: slChoose];//replace with localized string "choose"
#ifdef bDoDebug
NSLog(#"aPrintServers: %#\n", aPrintServers);
#endif
}
//Now comes the tedious part to extract only the print-server-names from the single lines
NSRange r;
NSString* sTemp;
for (int i = 1; i < [aPrintServers count]; i++) {//skip first line with "choose". To get rid of the rest of the line, we must isolate/preserve the print server's name to the delimiting comma and remove all the remaining characters
sTemp = [aPrintServers objectAtIndex: i];
sTemp = [sTemp stringByTrimmingCharactersInSet: [NSCharacterSet whitespaceAndNewlineCharacterSet]];//remove newlines and line feeds
#ifdef bDoDebug
NSLog(#"sTemp: %#\n", sTemp);
#endif
r = [sTemp rangeOfString: #","];//now find first comma to remove the whole rest of the line
//r.length = [sTemp lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
r.length = [sTemp length] - r.location;//calculate number of chars between first comma found and lenght of string
#ifdef bDoDebug
NSLog(#"range: %i, %i\n", r.location, r.length);
#endif
sTemp = [sTemp stringByReplacingCharactersInRange:r withString: #"" ];//remove rest of line
#ifdef bDoDebug
NSLog(#"sTemp after replace: %#\n", sTemp);
#endif
[aPrintServers replaceObjectAtIndex: i withObject: sTemp];//put back string into array for display in comboBox
#ifdef bDoDebug
NSLog(#"aPrintServer: %#\n", [aPrintServers objectAtIndex: i]);
#endif
}
[comboPrintServer removeAllItems];//reset combo box
[comboPrintServer addItemsWithObjectValues:aPrintServers];
[comboPrintServer setNumberOfVisibleItems:aPrintServers.count];
[comboPrintServer selectItemAtIndex:0];
#ifdef bDoDebug
NSLog(#"comboPrintServer reloaded with new values.");
#endif
//release memory we used for LdapTask
[sLdapQueryCommand release];
[aLdapQueryArgs release];
[sLdapOutput release];
[fhLdapTask release];
[pipeLdapTask release];
// [tskLdapTask release];//strangely can not be explicitely released, might be autorelease anyway
// [mdLdapTask release];//strangely can not be explicitely released, might be autorelease anyway
[sTemp release];
}
}

Answer 9

I have my self come across instance where it was not enough to just separate string by component many tasks such as 1) Categorizing token into types 2) Adding new tokens 3)Separating string between custom closures like all words between "{" and "}"For any such requirements i found Parse Kit a life saver.
I used it to parse .PGN (prtable gaming notation) files successfully its very fast and lite.