I am trying to parse a large string in order to isolate words and all punctuation. Java has the following constructor for its StringTokenizer class.
public StringTokenizer(String str, String delim, boolean returnDelims)
Notice the last parameter. If that is true, each delimiter is also returned as a token.
Is there a class in Obj-C that mimics this Java functionality? I have been able to parse the string, but I lose my delimiters in the process and those delimiters determine what I do next.
According to the CFStringTokenizer reference, it tokenizes into "words, sentences, and paragraphs". I need more granularity than that.
Appreciate the help.
You can just use the componentsSeparatedByString: method of NSString and then NSMutableArray to insert the delimiters between the substrings:
NSString *s = #"abc,def,ghi,jkl";
NSString *delim = #",";
NSArray *arr = [s componentsSeparatedByString:delim];
NSMutableArray *res = [NSMutableArray array];
[res addObject:arr[0]];
for (NSInteger i = 1; i < arr.count; i++) {
[res addObject:delim];
[res addObject:arr[i]];
}
NSLog(#"%#", res);
Here is a sample category on NSScanner that may get you started:
#implementation NSScanner (Tokenizer)
+ (NSArray *)tokenize(NSString *str,NSString *delim,BOOL returnDelims)
{
NSScanner *scanner=[NSScanner scannerWithString:str];
NSString *delimiters=[NSCharacterSet characterSetWithCharactersInString:#",.!;"];
NSMutableArray *ma=[NSMutableArray array];
NSString *s;
while(![scanner isAtEnd])
{
if([scanner scanUpToCharactersFromSet:delim intoString:&s])
{
[ma addObject:s];
}
if([scanner scanCharactersFromSet:delim intoString:&s])
{
if(returnDelims) [ma addObject:s];
}
}
return ma;
}
#end
This isn't a complete implementation, it doesn't deal with whitespace or enforcing a specific order in the array. But it should give you an idea.
Related
I have an NSString which is a mathematical expression. I have operators (+,-,*,/) and operands (digits from 0 to 9,integers,decimals etc). I want to convert this NSString into NSArray. For example if my NSString is "7.9999-1.234*-9.21". I want NSArray having elements 7.9999,-,1.234,*,-,9.21 in the same order. How can I accomplish this?
I have tried a code. It dosent work in all scenarios though. Here It is:
code:
NSString *str=#"7.9999-1.234*-9.21";
NSMutableArray *marray=[[NSMutableArray alloc] init];
for(i=0;i<6;i++)
{
[marray addObject:[NSNull null]];
}
NSMutableArray *operands=[[NSMutableArray alloc] initWithObjects:#"7.9999",#"1.234",#"9.21",nil];
NSMutableArray *operators=[[NSMutableArray alloc] initWithObjects:#"-",#"*",#"-",nil];
for(i=0,j=0,k=0,l=0;i<=([str length]-1),j<[operands count],k<[operators count],l<[marray count];i++)
{
NSString *element=[[NSString alloc] initWithFormat:#"%c",[str characterAtIndex:i]];
BOOL res=[element isEqualToString:#"+"]||[element isEqualToString:#"-"]||[element isEqualToString:#"*"]||[element isEqualToString:#"/"];
if(res==0)
{
[marray replaceObjectAtIndex:l withObject:[operands objectAtIndex:j]];
}
else
{
l++;
[marray replaceObjectAtIndex:l withObject:[operators objectAtIndex:k]];
k++,l++,j++;
}
}
for(i=0;i<6;i++)
{
NSLog(#"%#",[marray objectAtIndex:i]);
}
Here str is the string to be converted. My array is the array obtained by converting the string str. When I execute this code I get the following on console:
7.9999
-
1.234
*
<null>
-
You should use NSScanner, scanning up to your operator characters, then when you find one, save the scanned string and then save the operator into the array and skip the operator (setScanLocation:). Continue doing this till you get to the end of the string (in a loop, one iteration for each operator).
NSArray * marray = [str componentsSeparatedByCharactersInSet:
[NSCharacterSet characterSetWithCharactersInString:#"+-*/"]
];
ThankYou #Wain and #Hinata Hyuga.I figured out a code that would work to convert any string to array with the help of your suggestions.
Here is the code
NSMutableArray *convArray=[[NSMutableArray alloc] init];
NSScanner *scanner = [NSScanner scannerWithString:inputString];
NSCharacterSet *opSet=[NSCharacterSet characterSetWithCharactersInString:#"+-/*"];
[scanner setCharactersToBeSkipped:opSet];
int i;
for(i=0;i<[inputString length];)
{
if([inputString characterAtIndex:i]=='+'||[inputString characterAtIndex:i]=='-'||[inputString characterAtIndex:i]=='*'||[inputString characterAtIndex:i]=='/')
{
[convArray addObject:[[NSString alloc] initWithFormat:#"%c",[inputString characterAtIndex:i]]];
i++;
}
else
{
NSString *oprnd;
[scanner scanUpToCharactersFromSet:opSet intoString:&oprnd];
[convArray addObject:oprnd];
i=i+[inputString rangeOfString:oprnd].length;
}
}
return convArray;
I'v been trying to split string to array of components by number, but have no idea how to do it. I know that each components lenght is 9 except the last one. But there is no separation between them. Maybe anyone would know how could i make this split possible?
string : E44000000R33000444V33441
And i'd like to get array with: E44000000 R33000444 V33441
in past I'v used this method, but i guess there should be a way to separate by constant number. Any ideas
NSArray *myWords = [message componentsSeparatedByString:#";"];
Please try the below code.
NSString *stringTest = #"E44000000R33000444V33441323";
NSMutableArray *arrayTest = [NSMutableArray array];
while([stringTest length] > 8) {
[arrayTest addObject:[NSString stringWithString:[stringTest substringToIndex:9]]];
stringTest = [stringTest substringFromIndex:9];
}
NSLog(#"arrayTest - %#", arrayTest);
Try this one..
NSString *mainString=#"E44000000R33000444V";
NSMutableArray *brokenString=[NSMutableArray new];
int start=0;
for (; start<mainString.length-9; start+=9) {
[brokenString addObject:[mainString substringWithRange:NSMakeRange(start, 9)]];
}
[brokenString addObject:[mainString substringFromIndex:start]];
NSLog(#"->%#",brokenString);
Output is :
->(
E44000000,
R33000444,
V
)
I investigated the NSString, and i didn't found any function like that. But you can create a category of NSString and put this function in that category and you can use as a NSString instance method.
- (NSArray *) componentSaparetedByLength:(NSUInteger) length{
NSMutableArray *array = [NSMutableArray new];
NSRange range = NSMakeRange(0, length);
NSString *subString = nil;
while (range.location + range.length <= self.length) {
subString = [self substringWithRange:range];
[array addObject:subString];
//Edit
range.location = range.length + range.location;
//Edit
range.length = length;
}
if(range.location<self.length){
subString = [self substringFromIndex:range.location];
[array addObject:subString];
}
return array;
}
You can get the substring upto the characters which you want in a loop(string length) & pass the next index for getting the next substring. After getting each substring you can add it to the array.
Used SubstringToIndex & SubstringFromIndex functions to get the substring.
Also not an requirement here, I want to propose a solution that is capable of handling characters from more sophisticated script systems, like surrogate pairs, base characters plus combining marks, Hangul jamo, and Indic consonant clusters.
#interface NSString (Split)
-(NSArray *)arrayBySplittingWithMaximumSize:(NSUInteger)size
options:(NSStringEnumerationOptions) option;
#end
#implementation NSString (Split)
-(NSArray *)arrayBySplittingWithMaximumSize:(NSUInteger)size
options:(NSStringEnumerationOptions) option
{
NSMutableArray *letterArray = [NSMutableArray array];
[self enumerateSubstringsInRange:NSMakeRange(0, [self length])
options:(option)
usingBlock:^(NSString *substring,
NSRange substringRange,
NSRange enclosingRange,
BOOL *stop) {
[letterArray addObject:substring];
}];
NSMutableArray *array = [NSMutableArray array];
[letterArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
if (idx%size == 0) {
[array addObject: [NSMutableString stringWithCapacity:size]];
}
NSMutableString *string = [array objectAtIndex:[array count]-1];
[string appendString:obj];
}];
return array;
}
#end
usage
NSArray *array = [#"E44000000R33000444V33441" arraysBySplittingWithMaximumSize:9
options:NSStringEnumerationByComposedCharacterSequences];
results in:
(
E44000000,
R33000444,
V33441
)
I'm trying to re-arrange words into alphabetical order. For example, tomato would become amoott, or stack would become ackst.
I've found some methods to do this in C with char arrays, but I'm having issues getting that to work within the confines of the NSString object.
Is there an easier way to do it within the NSString object itself?
You could store each of the string's characters into an NSArray of NSNumber objects and then sort that. Seems a bit expensive, so I would perhaps just use qsort() instead.
Here it's provided as an Objective-C category (untested):
NSString+SortExtension.h:
#import <Foundation/Foundation.h>
#interface NSString (SortExtension)
- (NSString *)sorted;
#end
NSString+SortExtension.m:
#import "NSString+SortExtension.h"
#implementation NSString (SortExtension)
- (NSString *)sorted
{
// init
NSUInteger length = [self length];
unichar *chars = (unichar *)malloc(sizeof(unichar) * length);
// extract
[self getCharacters:chars range:NSMakeRange(0, length)];
// sort (for western alphabets only)
qsort_b(chars, length, sizeof(unichar), ^(const void *l, const void *r) {
unichar left = *(unichar *)l;
unichar right = *(unichar *)r;
return (int)(left - right);
});
// recreate
NSString *sorted = [NSString stringWithCharacters:chars length:length];
// clean-up
free(chars);
return sorted;
}
#end
I think separate the string to an array of string(each string in the array contains only one char from the original string). Then sort the array will be OK. This is not efficient but is enough when the string is not very long. I've tested the code.
NSString *str = #"stack";
NSMutableArray *charArray = [NSMutableArray arrayWithCapacity:str.length];
for (int i=0; i<str.length; ++i) {
NSString *charStr = [str substringWithRange:NSMakeRange(i, 1)];
[charArray addObject:charStr];
}
NSString *sortedStr = [[charArray sortedArrayUsingSelector:#selector(localizedCaseInsensitiveCompare:)] componentsJoinedByString:#""];
// --------- Function To Make an Array from String
NSArray *makeArrayFromString(NSString *my_string) {
NSMutableArray *array = [[NSMutableArray alloc] init];
for (int i = 0; i < my_string.length; i ++) {
[array addObject:[NSString stringWithFormat:#"%c", [my_string characterAtIndex:i]]];
}
return array;
}
// --------- Function To Sort Array
NSArray *sortArrayAlphabetically(NSArray *my_array) {
my_array= [my_array sortedArrayUsingSelector:#selector(localizedCaseInsensitiveCompare:)];
return my_array;
}
// --------- Function Combine Array To Single String
NSString *combineArrayIntoString(NSArray *my_array) {
NSString * combinedString = [[my_array valueForKey:#"description"] componentsJoinedByString:#""];
return combinedString;
}
// Now you can call the functions as in below where string_to_arrange is your string
NSArray *blowUpArray;
blowUpArray = makeArrayFromString(string_to_arrange);
blowUpArray = sortArrayAlphabetically(blowUpArray);
NSString *arrayToString= combineArrayIntoString(blowUpArray);
NSLog(#"arranged string = %#",arrayToString);
Just another example using NSMutableString and sortUsingComparator:
NSMutableString *mutableString = [[NSMutableString alloc] initWithString:#"tomat"];
[mutableString appendString:#"o"];
NSLog(#"Orignal string: %#", mutableString);
NSMutableArray *charArray = [NSMutableArray array];
for (int i = 0; i < mutableString.length; ++i) {
[charArray addObject:[NSNumber numberWithChar:[mutableString characterAtIndex:i]]];
}
[charArray sortUsingComparator:^NSComparisonResult(id _Nonnull obj1, id _Nonnull obj2) {
if ([obj1 charValue] < [obj2 charValue]) return NSOrderedAscending;
return NSOrderedDescending;
}];
[mutableString setString:#""];
for (int i = 0; i < charArray.count; ++i) {
[mutableString appendFormat:#"%c", [charArray[i] charValue]];
}
NSLog(#"Sorted string: %#", mutableString);
Output:
Orignal string: tomato
Sorted string: amoott
I have a search string, where people can use quotes to group phrases together, and mix this with individual keywords. For example, a string like this:
"Something amazing" rooster
I'd like to separate that into an NSArray, so that it would have Something amazing (without quotes) as one element, and rooster as the other.
Neither componentsSeparatedByString nor componentsSeparatedByCharactersInSet seem to fit the bill. Is there an easy way to do this, or should I just code it up myself?
You probably will have to code some of this up yourself, but the NSScanner should be a good basis on which to build. If you use the scanUpToCharactersInSet method to look for everything up to your next whitespace or quote character to can pick off words. Once you encounter a quite character, you could continue to scan using just the quote in the character set to end at, so that spaces within the quotes don't result in the end of a token.
I made a simple way to do this using NSScanner:
+ (NSArray *)arrayFromTagString:(NSString *)string {
NSScanner *scanner = [NSScanner scannerWithString:string];
NSString *substring;
NSMutableArray *array = [[NSMutableArray alloc] init];
while (scanner.scanLocation < string.length) {
// test if the first character is a quote
unichar character = [string characterAtIndex:scanner.scanLocation];
if (character == '"') {
// skip the first quote and scan everything up to the next quote into a substring
[scanner setScanLocation:(scanner.scanLocation + 1)];
[scanner scanUpToString:#"\"" intoString:&substring];
[scanner setScanLocation:(scanner.scanLocation + 1)]; // skip the second quote too
}
else {
// scan everything up to the next space into the substring
[scanner scanUpToString:#" " intoString:&substring];
}
// add the substring to the array
[array addObject:substring];
//if not at the end, skip the space character before continuing the loop
if (scanner.scanLocation < string.length) [scanner setScanLocation:(scanner.scanLocation + 1)];
}
return array.copy;
}
This method will convert the array back to a tag string, re-quoting the multi-word tags:
+ (NSString *)tagStringFromArray:(NSArray *)array {
NSMutableString *string = [[NSMutableString alloc] init];
NSRange range;
for (NSString *substring in array) {
if (string.length > 0) {
[string appendString:#" "];
}
range = [substring rangeOfString:#" "];
if (range.location != NSNotFound) {
[string appendFormat:#"\"%#\"", substring];
}
else [string appendString:substring];
}
return string.description;
}
I ended up going with a regular expression as I was already using RegexKitLite, and creating this NSString+SearchExtensions category.
.h:
// NSString+SearchExtensions.h
#import <Foundation/Foundation.h>
#interface NSString (SearchExtensions)
-(NSArray *)searchParts;
#end
.m:
// NSString+SearchExtensions.m
#import "NSString+SearchExtensions.h"
#import "RegexKitLite.h"
#implementation NSString (SearchExtensions)
-(NSArray *)searchParts {
__block NSMutableArray *items = [[NSMutableArray alloc] initWithCapacity:5];
[self enumerateStringsMatchedByRegex:#"\\w+|\"[\\w\\s]*\"" usingBlock: ^(NSInteger captureCount,
NSString * const capturedStrings[captureCount],
const NSRange capturedRanges[captureCount],
volatile BOOL * const stop) {
NSString *result = [capturedStrings[0] stringByReplacingOccurrencesOfRegex:#"\"" withString:#""];
NSLog(#"Match: '%#'", result);
[items addObject:result];
}];
return [items autorelease];
}
#end
This returns an NSArray of strings with the search strings, removing the double quotes that surround the phrases.
If you'll allow a slightly different approach, you could try Dave DeLong's CHCSVParser. It is intended to parse CSV strings, but if you set the space character as the delimiter, I am pretty sure you will get the intended behavior.
Alternatively, you can peek into the code and see how it handles quoted fields - it is published under the MIT license.
I would run -componentsSeparatedByString:#"\"" first, then create a BOOL isPartOfQuote, initialized to YES if the first character of the string was a ", but otherwise set to NO.
Then create a mutable array to return:
NSMutableArray* masterArray = [[NSMutableArray alloc] init];
Then, create a loop over the array returned from the separation:
for(NSString* substring in firstSplitArray) {
NSArray* secondSplit;
if (isPartOfQuote == NO) {
secondSplit = [substring componentsSeparatedByString:#" "];
}
else {
secondSplit = [NSArray arrayWithObject: substring];
}
[masterArray addObjectsFromArray: secondSplit];
isPartOfQuote = !isPartOfQuote;
}
Then return masterArray from the function.
Is there any way to create a new
NSString from a format string like #"xxx=%#, yyy=%#" and a NSArray of objects?
In the NSSTring class there are many methods like:
- (id)initWithFormat:(NSString *)format arguments:(va_list)argList
- (id)initWithFormat:(NSString *)format locale:(id)locale arguments:(va_list)argList
+ (id)stringWithFormat:(NSString *)format, ...
but non of them takes a NSArray as an argument, and I cannot find a way to create a va_list from a NSArray...
It is actually not hard to create a va_list from an NSArray. See Matt Gallagher's excellent article on the subject.
Here is an NSString category to do what you want:
#interface NSString (NSArrayFormatExtension)
+ (id)stringWithFormat:(NSString *)format array:(NSArray*) arguments;
#end
#implementation NSString (NSArrayFormatExtension)
+ (id)stringWithFormat:(NSString *)format array:(NSArray*) arguments
{
char *argList = (char *)malloc(sizeof(NSString *) * arguments.count);
[arguments getObjects:(id *)argList];
NSString* result = [[[NSString alloc] initWithFormat:format arguments:argList] autorelease];
free(argList);
return result;
}
#end
Then:
NSString* s = [NSString stringWithFormat:#"xxx=%#, yyy=%#" array:#[#"XXX", #"YYY"]];
NSLog( #"%#", s );
Unfortunately, for 64-bit, the va_list format has changed, so the above code no longer works. And probably should not be used anyway given it depends on the format that is clearly subject to change. Given there is no really robust way to create a va_list, a better solution is to simply limit the number of arguments to a reasonable maximum (say 10) and then call stringWithFormat with the first 10 arguments, something like this:
+ (id)stringWithFormat:(NSString *)format array:(NSArray*) arguments
{
if ( arguments.count > 10 ) {
#throw [NSException exceptionWithName:NSRangeException reason:#"Maximum of 10 arguments allowed" userInfo:#{#"collection": arguments}];
}
NSArray* a = [arguments arrayByAddingObjectsFromArray:#[#"X",#"X",#"X",#"X",#"X",#"X",#"X",#"X",#"X",#"X"]];
return [NSString stringWithFormat:format, a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8], a[9] ];
}
Based on this answer using Automatic Reference Counting (ARC): https://stackoverflow.com/a/8217755/881197
Add a category to NSString with the following method:
+ (id)stringWithFormat:(NSString *)format array:(NSArray *)arguments
{
NSRange range = NSMakeRange(0, [arguments count]);
NSMutableData *data = [NSMutableData dataWithLength:sizeof(id) * [arguments count]];
[arguments getObjects:(__unsafe_unretained id *)data.mutableBytes range:range];
NSString *result = [[NSString alloc] initWithFormat:format arguments:data.mutableBytes];
return result;
}
One solution that came to my mind is that I could create a method that works with a fixed large number of arguments like:
+ (NSString *) stringWithFormat: (NSString *) format arguments: (NSArray *) arguments {
return [NSString stringWithFormat: format ,
(arguments.count>0) ? [arguments objectAtIndex: 0]: nil,
(arguments.count>1) ? [arguments objectAtIndex: 1]: nil,
(arguments.count>2) ? [arguments objectAtIndex: 2]: nil,
...
(arguments.count>20) ? [arguments objectAtIndex: 20]: nil];
}
I could also add a check to see if the format string has more than 21 '%' characters and throw an exception in that case.
#Chuck is correct about the fact that you can't convert an NSArray into varargs. However, I don't recommend searching for the pattern %# in the string and replacing it each time. (Replacing characters in the middle of a string is generally quite inefficient, and not a good idea if you can accomplish the same thing in a different way.) Here is a more efficient way to create a string with the format you're describing:
NSArray *array = ...
NSAutoreleasePool *pool = [NSAutoreleasePool new];
NSMutableArray *newArray = [NSMutableArray arrayWithCapacity:[array count]];
for (id object in array) {
[newArray addObject:[NSString stringWithFormat:#"x=%#", [object description]]];
}
NSString *composedString = [[newArray componentsJoinedByString:#", "] retain];
[pool drain];
I included the autorelease pool for good housekeeping, since an autoreleased string will be created for each array entry, and the mutable array is autoreleased as well. You could easily make this into a method/function and return composedString without retaining it, and handle the autorelease elsewhere in the code if desired.
This answer is buggy. As noted, there is no solution to this problem that is guaranteed to work when new platforms are introduced other than using the "10 element array" method.
The answer by solidsun was working well, until I went to compile with 64-bit architecture. This caused an error:
EXC_BAD_ADDRESS type EXC_I386_GPFLT
The solution was to use a slightly different approach for passing the argument list to the method:
+ (id)stringWithFormat:(NSString *)format array:(NSArray*) arguments;
{
__unsafe_unretained id * argList = (__unsafe_unretained id *) calloc(1UL, sizeof(id) * arguments.count);
for (NSInteger i = 0; i < arguments.count; i++) {
argList[i] = arguments[i];
}
NSString* result = [[NSString alloc] initWithFormat:format, *argList] ;// arguments:(void *) argList];
free (argList);
return result;
}
This only works for arrays with a single element
There is no general way to pass an array to a function or method that uses varargs. In this particular case, however, you could fake it by using something like:
for (NSString *currentReplacement in array)
[string stringByReplacingCharactersInRange:[string rangeOfString:#"%#"]
withString:currentReplacement];
EDIT: The accepted answer claims there is a way to do this, but regardless of how fragile this answer might seem, that approach is far more fragile. It relies on implementation-defined behavior (specifically, the structure of a va_list) that is not guaranteed to remain the same. I maintain that my answer is correct and my proposed solution is less fragile since it only relies on defined features of the language and frameworks.
For those who need a Swift solution, here is an extension to do this in Swift
extension String {
static func stringWithFormat(format: String, argumentsArray: Array<AnyObject>) -> String {
let arguments = argumentsArray.map { $0 as! CVarArgType }
let result = String(format:format, arguments:arguments)
return result
}
}
Yes, it is possible. In GCC targeting Mac OS X, at least, va_list is simply a C array, so you'll make one of ids, then tell the NSArray to fill it:
NSArray *argsArray = [[NSProcessInfo processInfo] arguments];
va_list args = malloc(sizeof(id) * [argsArray count]);
NSAssert1(args != nil, #"Couldn't allocate array for %u arguments", [argsArray count]);
[argsArray getObjects:(id *)args];
//Example: NSLogv is the version of NSLog that takes a va_list instead of separate arguments.
NSString *formatSpecifier = #"\n%#";
NSString *format = [#"Arguments:" stringByAppendingString:[formatSpecifier stringByPaddingToLength:[argsArray count] * 3U withString:formatSpecifier startingAtIndex:0U]];
NSLogv(format, args);
free(args);
You shouldn't rely on this nature in code that should be portable. iPhone developers, this is one thing you should definitely test on the device.
- (NSString *)stringWithFormat:(NSString *)format andArguments:(NSArray *)arguments {
NSMutableString *result = [NSMutableString new];
NSArray *components = format ? [format componentsSeparatedByString:#"%#"] : #[#""];
NSUInteger argumentsCount = [arguments count];
NSUInteger componentsCount = [components count] - 1;
NSUInteger iterationCount = argumentsCount < componentsCount ? argumentsCount : componentsCount;
for (NSUInteger i = 0; i < iterationCount; i++) {
[result appendFormat:#"%#%#", components[i], arguments[i]];
}
[result appendString:[components lastObject]];
return iterationCount == 0 ? [result stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] : result;
}
Tested with format and arguments:
NSString *format = #"xxx=%#, yyy=%# last component";
NSArray *arguments = #[#"XXX", #"YYY", #"ZZZ"];
Result: xxx=XXX, yyy=YYY last component
NSString *format = #"xxx=%#, yyy=%# last component";
NSArray *arguments = #[#"XXX", #"YYY"];
Result: xxx=XXX, yyy=YYY last component
NSString *format = #"xxx=%#, yyy=%# last component";
NSArray *arguments = #[#"XXX"];
Result: xxx=XXX last component
NSString *format = #"xxx=%#, yyy=%# last component";
NSArray *arguments = #[];
Result: last component
NSString *format = #"some text";
NSArray *arguments = #[#"XXX", #"YYY", #"ZZZ"];
Result: some text
I found some code on the web that claims that this is possible however I haven't managed to do it myself, however if you don't know the number of arguments in advance you also need to build the format string dynamically so I just don't see the point.
You better off just building the string by iterating the array.
You might find the stringByAppendingString: or stringByAppendingFormat: instance method handy .
One can create a category for NSString and make a function which receives a format, an array and returns the string with replaced objects.
#interface NSString (NSArrayFormat)
+ (NSString *)stringWithFormat:(NSString *)format arrayArguments:(NSArray *)arrayArguments;
#end
#implementation NSString (NSArrayFormat)
+ (NSString *)stringWithFormat:(NSString *)format arrayArguments:(NSArray *)arrayArguments {
static NSString *objectSpecifier = #"%#"; // static is redundant because compiler will optimize this string to have same address
NSMutableString *string = [[NSMutableString alloc] init]; // here we'll create the string
NSRange searchRange = NSMakeRange(0, [format length]);
NSRange rangeOfPlaceholder = NSMakeRange(NSNotFound, 0); // variables are declared here because they're needed for NSAsserts
NSUInteger index;
for (index = 0; index < [arrayArguments count]; ++index) {
rangeOfPlaceholder = [format rangeOfString:objectSpecifier options:0 range:searchRange]; // find next object specifier
if (rangeOfPlaceholder.location != NSNotFound) { // if we found one
NSRange substringRange = NSMakeRange(searchRange.location, rangeOfPlaceholder.location - searchRange.location);
NSString *formatSubstring = [format substringWithRange:substringRange];
[string appendString:formatSubstring]; // copy the format from previous specifier up to this one
NSObject *object = [arrayArguments objectAtIndex:index];
NSString *objectDescription = [object description]; // convert object into string
[string appendString:objectDescription];
searchRange.location = rangeOfPlaceholder.location + [objectSpecifier length]; // update the search range in order to minimize search
searchRange.length = [format length] - searchRange.location;
} else {
break;
}
}
if (rangeOfPlaceholder.location != NSNotFound) { // we need to check if format still specifiers
rangeOfPlaceholder = [format rangeOfString:#"%#" options:0 range:searchRange];
}
NSAssert(rangeOfPlaceholder.location == NSNotFound, #"arrayArguments doesn't have enough objects to fill specified format");
NSAssert(index == [arrayArguments count], #"Objects starting with index %lu from arrayArguments have been ignored because there aren't enough object specifiers!", index);
return string;
}
#end
Because NSArray is created at runtime we cannot provide compile-time warnings, but we can use NSAssert to tell us if number of specifiers is equal with number of objects within array.
Created a project on Github where this category can be found. Also added Chuck's version by using 'stringByReplacingCharactersInRange:' plus some tests.
Using one million objects into array, version with 'stringByReplacingCharactersInRange:' doesn't scale very well (waited about 2 minutes then closed the app). Using the version with NSMutableString, function made the string in about 4 seconds. The tests were made using simulator. Before usage, tests should be done on a real device (use a device with lowest specs).
Edit: On iPhone 5s the version with NSMutableString takes 10.471655s (one million objects); on iPhone 5 takes 21.304876s.
Here's the answer without explicitly creating an array:
NSString *formattedString = [NSString stringWithFormat:#"%# World, Nice %#", #"Hello", #"Day"];
First String is the target string to be formatted, the next string are the string to be inserted in the target.
No, you won't be able to. Variable argument calls are solved at compile time, and your NSArray has contents only at runtime.