I want to ask an NSString * question. I have a NSString * object. The content is like the following example. (like the CSV file)
Example: (my file is longer than this one so much)
First Name,Last Name,Middle Name,Phone,Chan,Tim,Man,123-456-789,Tom,,,987-654-321
(if it is empty, no space between the ',')
How can I insert the "(null)" NSString * / or NSString * object between the two ',' by using the objective C?
// After convent
First Name,Last Name,Middle Name,Phone,Chan,Tim,Man,123-456-789,Tom,(null),(null),987-654-321
Thank you very much.
Have a look at the method stringByReplacingOccurrencesOfString:withString: (untested):
NSString *newString = [oldString stringByReplacingOccurrencesOfString:#",,"
withString:#",(null),"];
This might be sufficient for your needs.
I'm a beginner in Objective-C and I didn't test this answer, but I think it does the job.
//given your NSString called string
NSArray *pieces = [[NSArray alloc] initWithArray: [string componentsSeparatedByString:#","]];
NSMutableString *final = [[NSMutableString alloc] init];
for(int i; i < [pieces count]; i++)
{
if(i > 0)
[final appendString: [NSString stringWithFormat:#","]];
if([pieces objectAtIndex: [NSNumber numberWithInt: i]] == nil)
{
[final appendString: [NSString stringWithFormat:#"(null)"]];
}
else
{
[final appendString: [pieces objectAtIndex: [NSNumber numberWithInt: i]]];
}
}
I hope I didn't screw it up too bad :)
Related
I have a NSString formatted like this:
"Hello world 12 looking for some 56"
I want to find all instances of numbers separated by whitespace and place them in an NSArray. I dont want to remove the numbers though.
Whats the best way of achieving this?
This is a solution using regular expression as suggested in the comment.
NSString *string = #"Hello world 12 looking for some 56";
NSRegularExpression *expression = [NSRegularExpression regularExpressionWithPattern:#"\\b\\d+" options:nil error:nil];
NSArray *matches = [expression matchesInString:string options:nil range:(NSMakeRange(0, string.length))];
NSMutableArray *result = [[NSMutableArray alloc] init];
for (NSTextCheckingResult *match in matches) {
[result addObject:[string substringWithRange:match.range]];
}
NSLog(#"%#", result);
First make an array using NSString's componentsSeparatedByString method and take reference to this SO question. Then iterate the array and refer to this SO question to check if an array element is number: Checking if NSString is Integer.
I don't know where you are looking to do perform this action because it may not be fast (such as if it's being called in a table cell it may be choppy) based upon the string size.
Code:
+ (NSArray *)getNumbersFromString:(NSString *)str {
NSMutableArray *retVal = [NSMutableArray array];
NSCharacterSet *numericSet = [NSCharacterSet decimalDigitCharacterSet];
NSString *placeholder = #"";
unichar currentChar;
for (int i = [str length] - 1; i >= 0; i--) {
currentChar = [str characterAtIndex:i];
if ([numericSet characterIsMember:currentChar]) {
placeholder = [placeholder stringByAppendingString:
[NSString stringWithCharacters:¤tChar
length:[placeholder length]+1];
} else {
if ([placeholder length] > 0) [retVal addObject:[placeholder intValue]];
else placeholder = #"";
return [retVal copy];
}
To explain what is happening above, essentially I am,
going through every character until I find a number
adding that number including any numbers after to a string
once it finds a number it adds it to an array
Hope this helps please ask for clarification if needed
In Objective C, I have an object e.g. Person with a lot of fields firstName, lastName, phoneNumber, address, city... and so on. These fields types are NSString and any of these could be nil.
Now I want to concatenate my field values in another NSString :
Person *p = ...
NSMutableString *s = [[NSMutableString alloc] init];
for (NSString *field in #[p.firstName, p.lastName, p.phoneNumber,
p.adress, p.city, ....more fields...]) {
if ([field length] > 0) {
[s appendFormat:#"%#\n", field];
}
}
Issue is that this code crash whenever one of the field is nil. I have the exception :
[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object
from objects[0]'
How could I handle simply the case of nil values within my for loop ?
I agree with #TomPace's post, for this small number I would do a simple if/else.
However, there may be times you do need to loop through a list of fields.
It's a bad idea to blindly pull the values into an array as you could be trying inserting nil values into the array. In this case, it would be better to place the field names into a key array as strings and loop through the list using valueForKey: to access the values. I would possibly store the keys list somewhere else where it can be used again.
Person *p = ...
NSMutableString *s = [[NSMutableString alloc] init];
NSArray *keys = #[#"firstName", #"lastName", #"phoneNumber", #"adress", #"city"];
for (NSString *key in keys)
{
NSString *value = [p valueForKey:key];
if ([value length] > 0) {
[s appendFormat:#"%#\n", value];
}
}
Person *person = [[Person alloc] init];
person.firstName = nil;
person.lastName = #"lastName";
NSMutableString *s = [[NSMutableString alloc] init];
[s appendFormat:#"%#\n", person.firstName == nil?#"":person.firstName];
[s appendFormat:#"%#\n", person.lastName == nil?#"":person.lastName];
For a selection of fields this small, don't use a for loop.
You may be saving a bit of code by attempting the for-loop structure, but it's really not the way to go if you're building the NSArray with only a few fields, and especially because you can't put nil items in it.
A better way to go is:
Person *p = ...
NSMutableString *s = [[NSMutableString alloc] init];
if ([p.firstName length] > 0) [s appendFormat:#"%#\n", p.firstName];
if ([p.lastName length] > 0) [s appendFormat:#"%#\n", p.lastName];
if ([p.phoneNumber length] > 0) [s appendFormat:#"%#\n", p.phoneNumber];
if ([p.adress length] > 0) [s appendFormat:#"%#\n", p.adress];
if ([p.city length] > 0) [s appendFormat:#"%#\n", p.city];
Edit, after original Question was updated with large amount of fields.
Like #BergQuester said, an approach to support a larger, arbitrary set of fields is using KVO-style inspection.
NSArray *fieldNames = #[#"firstName", #"lastName", #"phoneNumber", ....more fields...];
NSString *field;
for (NSString *fieldName in fieldNames) {
field = [p valueForKey:fieldName];
if ([field length] > 0 ) {
[s appendFormat: #"%#\n", field];
}
}
Try to create NSMutableString category
#import "NSMutableString+checkForNilObject.h"
#implementation NSMutableString (checkForNilObject)
-(void) appendNotNillObject:(NSString *) string
{
if(string)
{
[self appendString:string];
}
}
#end
You can override the getters of the class Person.
#implementation Person
- (NSString *)firstName{
if (_firseName == nil)
_firstName = #"";
return _firstName;
}
///....Other setters
#end
Like this you can define all your setters here.
i'm programming in Obj-c with xcode4.1, i have an array with numbers in it, and i want to visualize all of them in a label...can anyone help me around this please?
thanks!
this is the code:
combinedString=[[NSMutableArray alloc] init];
NSString *finalStringLabel=#"";
for (i=0; i<=textLength; i++) {
//character coding
char myChar = [myString characterAtIndex:i];
NSString *myCharS=[NSString stringWithFormat:#"%c", myChar];
int asciiCode=[myCharS characterAtIndex:0];
NSString *asciiS=[NSString stringWithFormat:#"%i", asciiCode];
[combinedString addObject:asciiS];
}
finalStringLabel=[NSString stringWithFormat:#"", [combinedString componentsJoinedByString:#"."]];
myLabel.text=finalStringLabel;
[combinedString release];
}
You can use this
NSArray *yourArray;
NSString *createdString = [yourArray componentsJoinedByString:#" "];
myLabel.text = createdString;
As your array is combinedString,
combinedString=[[NSMutableArray alloc] init];
looks like you are providing values after this line or this is not a property (this is a local as you are releasing it later), and your code in not complete.
Anyways,
You don't need to create an empty string and then assign new object to it, need to do as :
myLabel.text=[combinedString componentsJoinedByString:#"."];
[combinedString release];
}
Is there a simple way to split a NSString into an array of characters? It would actually be best if the resulting type were a collection of NSString's themselves, just one character each.
Yes, I know I can do this in a loop, but I'm wondering if there is a faster way to do this with any existing methods or functions the way you can with LINQ in C#.
e.g.
// I have this...
NSString * fooString = #"Hello";
// And want this...
NSArray * fooChars; // <-- Contains the NSStrings, #"H", #"e", #"l", #"l" and #"o"
You could do something like this (if you want to use enumerators)
NSString *fooString = #"Hello";
NSMutableArray *characters = [[NSMutableArray alloc] initWithCapacity:[fooString length]];
[fooString enumerateSubstringsInRange:NSMakeRange(0, fooString.length)
options:NSStringEnumerationByComposedCharacterSequences
usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop) {
[characters addObject:substring];
}];
And if you really wanted it in an NSArray finally
NSArray *fooChars = [NSArray arrayWithArray:characters];
Be sure to care about that some characters like emoji and others may span a longer range than just one index.
Here's a category method for NSString
#implementation (SplitString)
- (NSArray *)splitString
{
NSUInteger index = 0;
NSMutableArray *array = [NSMutableArray arrayWithCapacity:self.length];
while (index < self.length) {
NSRange range = [self rangeOfComposedCharacterSequenceAtIndex:index];
NSString *substring = [self substringWithRange:range];
[array addObject:substring];
index = range.location + range.length;
}
return array;
}
#end
convert it to NSData the [data bytes] will have a C string in the encoding that you pick [data length] bytes long.
Try this
NSMutableArray *array = [NSMutableArray array];
NSString *str = #"Hello";
for (int i = 0; i < [str length]; i++) {
NSString *ch = [str substringWithRange:NSMakeRange(i, 1)];
[array addObject:ch];
}
Given a string, I need to obtain a count of each word that appears in that string. To do so, I extracted the string into an array, by word, and searched that way, but I have the feeling that searching the string directly is more optimal. Below is the code that I originally wrote to solve the problem. I'm up for suggestions on better solutions though.
NSMutableDictionary *sets = [[NSMutableDictionary alloc] init];
NSString *paragraph = [[NSString alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"text" ofType:#"txt"] encoding:NSUTF8StringEncoding error:NULL];
NSMutableArray *words = [[[paragraph lowercaseString] componentsSeparatedByString:#" "] mutableCopy];
while (words.count) {
NSMutableIndexSet *indexSet = [[NSMutableIndexSet alloc] init];
NSString *search = [words objectAtIndex:0];
for (unsigned i = 0; i < words.count; i++) {
if ([[words objectAtIndex:i] isEqualToString:search]) {
[indexSet addIndex:i];
}
}
[sets setObject:[NSNumber numberWithInt:indexSet.count] forKey:search];
[words removeObjectsAtIndexes:indexSet];
}
NSLog(#"%#", sets);
Example:
Starting string:
"This is a test. This is only a test."
Results:
"This" - 2
"is" - 2
"a" - 2
"test" - 2
"only" - 1
This is exactly what an NSCountedSet is for.
You need to break the string apart into words (which iOS is nice enough to give us a function for so that we don't have to worry about punctuation) and just add each of them to the counted set, which keeps track of the number of times each object appears in the set:
NSString *string = #"This is a test. This is only a test.";
NSCountedSet *countedSet = [NSCountedSet new];
[string enumerateSubstringsInRange:NSMakeRange(0, [string length])
options:NSStringEnumerationByWords | NSStringEnumerationLocalized
usingBlock:^(NSString *substring, NSRange substringRange, NSRange enclosingRange, BOOL *stop){
// This block is called once for each word in the string.
[countedSet addObject:substring];
// If you want to ignore case, so that "this" and "This"
// are counted the same, use this line instead to convert
// each word to lowercase first:
// [countedSet addObject:[substring lowercaseString]];
}];
NSLog(#"%#", countedSet);
// Results: 2012-11-13 14:01:10.567 Testing App[35767:fb03]
// <NSCountedSet: 0x885df70> (a [2], only [1], test [2], This [2], is [2])
If I had to guess, I would say NSRegularExpression for that. Like this:
NSUInteger numberOfMatches = [regex numberOfMatchesInString:string
options:0
range:NSMakeRange(0, [string length])];
That snippet was taken from here.
Edit 1.0:
Based on what Sir Till said:
NSString *string = #"This is a test, so it is a test";
NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
NSArray *arrayOfWords = [string componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
for (NSString *word in arrayOfWords)
{
if ([dictionary objectForKey:word])
{
NSNumber *numberOfOccurences = [dictionary objectForKey:word];
NSNumber *increment = [NSNumber numberWithInt:(1 + [numberOfOccurences intValue])];
[dictionary setValue:increment forKey:word];
}
else
{
[dictionary setValue:[NSNumber numberWithInt:1] forKey:word];
}
}
You should be careful with:
Punctuation signs. (near other words)
UpperCase words vs lowerCase words.
I think that's really bad idea that you trying to search a words among the long paragraph with a loop. You should use a regular expression to do that! I know it's not easy at first time to learn it but it's really worth to know it! Take look at this case Use regular expression to find/replace substring in NSString