I have an NSMutableArray which only lasts during the session.
Currently I create it like this
NSMutableArray *temp = [[NSMutableArray alloc] initWithCapacity:10];
[self setScoreArray:temp];
[temp release];
Problem is when I go to check each index I'm getting an array outofbounds error
NSNumber *previousScore = [[self scoreArray] objectAtIndex:[self quizNum]];
if ( previousScore != nil )
{
[self clearQuizBtns];
NSInteger previousScoreValue = [previousScore integerValue];
[self selectButtonAtTag:previousScoreValue];
}else {
[self clearQuizBtns];
}
I've read in other posts that initWithCapacity doesn't actually create the array. So what can I populate the array with initially?
Thanks in advance.
Two ways:
first: to initiate array with default values of NSNull class
NSMutableArray *temp = [[NSMutableArray alloc] initWithCapacity:10];
for (int i = 0 ; i < 10 ; i++)
{
[temp insertObject:[NSNull null] atIndex:i];
}
[self setScoreArray:temp];
[temp release];
and then to check: if object is kind of NSNull class means it was a never set before
id previousScore = [[self scoreArray] objectAtIndex:[self quizNum]];
if (![previousScore isKindOfClass:[NSNull class]])
{
[self clearQuizBtns];
NSInteger previousScoreValue = [(NSNumber *)previousScore integerValue];
[self selectButtonAtTag:previousScoreValue];
}else {
[self clearQuizBtns];
}
second: store scores in NSMutableDictionary and use NSNumber's as keys
// scoreDictionary property of NSMutableDictionary class must be declared in self
NSNumber *previousScore = [self.scoreDictionary objectForKey:[NSNumber numberWithInt:[self quizNum]]];
if (previousScore != nil)
{
[self clearQuizBtns];
NSInteger previousScoreValue = [previousScore integerValue];
[self selectButtonAtTag:previousScoreValue];
}else {
[self clearQuizBtns];
}
NSArray does not support "holes". The capacity is just a hint to the initializer.
You could either fill the array with placeholder objects or, more typically, change your algorithm to either fully prepopulate the array or to lazy load it linearly.
Your problem seems to be that you're never actually setting any score in the score array.. are you? NSArrays have an actual count of items in them, and accessing an index beyond that count will blow up, as you've seen. If there will only ever be a fixed (small) number of scores, like 10, then you could set them all initially to something default like:
for (int i = 0; i < 10; i++) {
[temp addObject:[NSNumber numberWithInt:0]];
}
P.S. -initWithCapacity does "create the array", it just doesn't create any objects in the array. The capacity is a hint only.
Using the arrayWithObject: or arrayWithObjects: methods can provide an array with pre-populated values.
One cool thing about NSMutableArrays is that you can just do an "init" and the array will handle adding and removing objects on the fly. Remember that you generally addObject: or removeObjectAtIndex: when dealing with mutable arrays.
Related
I want to get the index of an object within the NSMutableArray of categories.
The category object has an attribute "category_title" and I want to be able to get the index by passing the value of category_title.
I have looked through the docs and can't find a simple way to go about this.
NSArray does not guarantee that you can only store one copy of a given object, so you have to make sure that you handle that yourself (or use NSOrderedSet).
That said, there are a couple approaches here. If your category objects implement isEqual: to match category_title, then you can just use -indexOfObject:.
If you can't do that (because the category objects use a different definition of equality), use -indexOfObjectPassingTest:. It takes a block in which you can do whatever test you want to define your "test" - in this case, testing category_title string equality.
Note that these are all declared for NSArray, so you won't see them if you are only looking at the NSMutableArray header/documentation.
EDIT: Code sample. This assumes objects of class CASCategory with an NSString property categoryTitle (I can't bring myself to put underscores in an ivar name :-):
CASCategory *cat1 = [[CASCategory alloc] init];
[cat1 setCategoryTitle:#"foo"];
CASCategory *cat2 = [[CASCategory alloc] init];
[cat2 setCategoryTitle:#"bar"];
CASCategory *cat3 = [[CASCategory alloc] init];
[cat3 setCategoryTitle:#"baz"];
NSMutableArray *array = [NSMutableArray arrayWithObjects:cat1, cat2, cat3, nil];
[cat1 release];
[cat2 release];
[cat3 release];
NSUInteger barIndex = [array indexOfObjectPassingTest:^BOOL(id obj, NSUInteger idx, BOOL *stop) {
if ([[(CASCategory *)obj categoryTitle] isEqualToString:#"bar"]) {
*stop = YES;
return YES;
}
return NO;
}];
if (barIndex != NSNotFound) {
NSLog(#"The title of category at index %lu is %#", barIndex, [[array objectAtIndex:barIndex] categoryTitle]);
}
else {
NSLog(#"Not found");
}
Not sure that I understand the question but something like this might work (assuming the Mutable Array contains objects of Class "Category"):
int indx;
bool chk;
for (Category *aCategory in theArray)
{
chk = ([[aCategory category_title] isEqualToString:#"valOfCategoryTitle"])
if ( chk )
indx = [theArray indexOfObject:aCategory];
}
Try this code much more simpler:-
int f = [yourArray indexOfObject:#"yourString"];
The title pretty much says it all, but just to clarify: I have an NSMutableDictonary containing several NSMutableArrays. What I would like to do is find any value that is present in multiple arrays (there will not be any duplicates in a single array) and return that value. Can someone please help? Thanks in advance!
Edit: For clarity's sake I will specify some of my variables:
linesMutableDictionary contains a list of Line objects (which are a custom NSObject subclass of mine)
pointsArray is an array inside each Line object and contains the values I am trying to search through.
Basically I am trying to find out which lines share common points (the purpose of my app is geometry based)
- (NSValue*)checkForDupes:(NSMutableDictionary*)dict {
NSMutableArray *derp = [NSMutableArray array];
for (NSString *key in [dict allKeys]) {
Line *temp = (Line*)[dict objectForKey:key];
for (NSValue *val in [temp pointsArray]) {
if ([derp containsObject:val])
return val;
}
[derp addObjectsFromArray:[temp pointsArray]];
}
return nil;
}
this should work
If by duplicates you mean returning YES to isEqual: you could first make an NSSet of all the elements (NSSet cannot, by definition, have duplicates):
NSMutableSet* allElements = [[NSMutableSet alloc] init];
for (NSArray* array in [dictionary allValues]) {
[allElements addObjectsFromArray:array];
}
Now you loop through the elements and check if they are in multiple arrays
NSMutableSet* allDuplicateElements = [[NSMutableSet alloc] init];
for (NSObject* element in allElements) {
NSUInteger count = 0;
for (NSArray* array in [dictionary allValues]) {
if ([array containsObject:element]) count++;
if (count > 1) {
[allDuplicateElements addObject:element];
break;
}
}
}
Then you have your duplicate elements and don't forget to release allElements and allDuplicateElements.
I've got a problem. I'm trying to sort the items from 1 array (name: mps) into an other array (name: totalArray), but every item should be in a new array. In short: the items in mps should move into a new array, but every item should be in a new array, so the totalArray is an array of arrays. After that, totalArray should be copied back into mps.
To clarify, here is the code:
NSMutableString *oud = [[NSMutableString alloc] init];
NSMutableString *nieuw = [[NSMutableString alloc] init];
NSMutableArray *tempArray = [[NSMutableArray alloc] init];
[tempArray removeAllObjects];
NSMutableArray *totalArray = [[NSMutableArray alloc] init];
[totalArray removeAllObjects];
tempArray = [[NSMutableArray alloc] init];
[tempArray removeAllObjects];
for (int j = 0; j < [mps count]; j++)
{
nieuw = [[mps objectAtIndex:j] valueForKey:#"ConfigurationAlias"];
if (j != 0)
{
if ([oud rangeOfString:nieuw].location == NSNotFound)
{
NSLog(#"ADDED!");
[totalArray addObjectsFromArray:tempArray];
[oud setString:nieuw];
[tempArray removeAllObjects];
[tempArray addObject:[mps objectAtIndex:j]];
}
else
{
[tempArray addObject:[mps objectAtIndex:j]];
}
}
else {
[oud setString:nieuw];
[tempArray addObject:[mps objectAtIndex:j]];
}
}
//En de array weer laden in de tabel
//NSLog(#"%#", totalArray);
NSLog(#"%i", [mps count]);
[mps removeAllObjects];
NSLog(#"REMOVED!!!");
NSLog(#"%i", [mps count]);
[mps addObjectsFromArray:totalArray];
NSLog(#"Added totalArray: %i", [totalArray count]);
NSLog(#"%i", [mps count]);
[tempArray release];
[totalArray release];
[tabelView reloadData];
}
Now, here comes my problem:
The log gives the line 2011-04-07 10:02:46.368 Fleet Manager[901:40b] ADDED! 11 times, then it posts 16 (mps count, this is correct), then the line REMOVED!, then 0 (mps count, also correct), but then the line: Added totalArray: 15. This can't be correct, it added 11 times but it counts 15?
This a problem for me, in the first place because it's plain incorrect, but the tableview gets screwed up as well because of the section-amount not being correct either (15 sections). Anybody has any idea what's going on?
EDIT: all the objects in mps are dictionaries, and all of them have a value for the key "ConfigurationAlias".
First, I would like to suggest using debugging mode instead of bunch of NSLog functions to track down what's actually happening inside your objects and variables. Try using breakpoints. Set one for [totalArray addObjectsFromArray:tempArray]; line so every time this line of code is reached the execution would stop and let you look around, check different fields' states inside totalArray and tempArray objects.
Concerning your problem... Since you are using addObjectsFromArray: that means that passed array may pass not one but several objects (thus the plural in method name). I guess one of those "11 times" added more than one element - that should explain the actual count being more than the times you've called this method. Again, please check tempArray contents.
Good luck!
If you want to end up with an array of arrays, you need to be allocating temp arrays inside the loop. It also seems like you are overdoing it with clearing out the arrays.
It appears you are trying to add the value from mps to totalArray regardless of the conditions, so it would make sense to only do that in one place (outside of the conditions).
Also, if you are not mutating the arrays (such as tempArray), you can use NSArray instead, which should be smaller and faster.
Finally, you should be able to assign the new array to mps instead of doing the expensive array copying. Not sure if that is somehow referenced as the table delegate, though.
I would try something like:
NSMutableString *oud = [[NSMutableString alloc] init];
NSMutableString *nieuw = [[NSMutableString alloc] init];
NSMutableArray *tempArray;
NSMutableArray *totalArray = [[NSMutableArray alloc] init];
for (int j = 0; j < [mps count]; j++)
{
tempArray = [[NSMutableArray alloc] init];
[totalArray addObject:tempArray];
[tempArray release];
nieuw = [[mps objectAtIndex:j] valueForKey:#"ConfigurationAlias"];
if (j != 0)
{
if ([oud rangeOfString:nieuw].location == NSNotFound)
{
NSLog(#"ADDED!");
[oud setString:nieuw];
}
}
else {
[oud setString:nieuw];
}
}
NSLog(#"%i", [mps count]);
[mps removeAllObjects];
NSLog(#"REMOVED!!!");
NSLog(#"%i", [mps count]);
[mps addObjectsFromArray:totalArray];
NSLog(#"Added totalArray: %i", [totalArray count]);
NSLog(#"%i", [mps count]);
[totalArray release];
[tabelView reloadData];
}
You should
sort the base array in a tempArray
create an empty resultArray
iterate through tempArray and for each item create an itemArray containing the item on the first position and add this array to resutArray
don't forget to release all alloc-ed temporary data
Check this out for sorting easily: Sorting arrays via Apple
I'm working on implementing a customized searchBar for a fairly complex table and have come across this code pattern AGAIN. This is a sample from the Beginning iPhone Development book:
- (void)handleSearchForTerm:(NSString *)searchTerm
{
NSMutableArray *sectionsToRemove = [[NSMutableArray alloc] init];
[self resetSearch];
for (NSString *key in self.keys)
{
NSMutableArray *array = [self.names valueForKey:key];
NSMutableArray *toRemove = [[NSMutableArray alloc] init];
for (NSString *name in array)
{
if ([name rangeOfString:searchTerm
options:NSCaseInsensitiveSearch].location == NSNotFound)
[toRemove addObject:name];
}
if ([array count] == [toRemove count])
[sectionsToRemove addObject:key];
[array removeObjectsInArray:toRemove];
[toRemove release];
}
[self.keys removeObjectsInArray:sectionsToRemove];
[sectionsToRemove release];
[table reloadData];
}
The part I'm curious about is the "for (NSString *name in array)" section. What is this doing exactly? It seems to create a string for every item in the array. Also, how does this work with dictionaries?
Thanks!
This construct is a different kind of for loop that runs over items in an Objective-C collection, rather than a C array. The first part defines an object that is being set to one element in the collection each run of the loop, while the second part is the collection to enumerate. For example, the code:
NSArray *array = [NSArray arrayWithObjects:#"foo", #"bar", nil];
for(NSString *string in array) {
NSLog(string);
}
would print:
foo
bar
It's defining an NSString *string that, each run of the loop, gets set to the next object in the NSArray *array.
Similarly, you can use enumeration with instances of NSSet (where the order of objects aren't defined) and NSDictionary (where it will enumerate over keys stored in the dictionary - you can enumerate over the values by enumerating over keys, then calling valueForKey: on the dictionary using that key).
It's extremely similar to the construct in C:
int array[2] = { 0, 1 };
for(int i = 0; i < 2; i++) {
printf("%d\n", array[i]);
}
which prints:
0
1
It's just a syntactical way of making the code more readable and hiding some of the fancy enumeration that goes into listing objects in an NSArray, NSSet, or NSDictionary. More detail is given in the Fast Enumeration section of The Objective-C 2.0 Programming Language document.
This is called fast enumeration. It loops through the array, setting key to each item. It's the same, functionally, as doing this:
NSString *key;
for ( NSInteger i = 0; i < [[ self keys ] count ]; i++ ) {
key = [[ self keys ] objectAtIndex:i ];
NSMutableArray *array = [self.names valueForKey:key];
NSMutableArray *toRemove = [[NSMutableArray alloc] init];
for (NSString *name in array)
{
if ([name rangeOfString:searchTerm
options:NSCaseInsensitiveSearch].location == NSNotFound)
[toRemove addObject:name];
}
if ([array count] == [toRemove count])
[sectionsToRemove addObject:key];
[array removeObjectsInArray:toRemove];
[toRemove release];
}
It's a for loop with one iteration for each key in the dictionary.
The for..in construct is called Fast enumeration. You can read more about it in Objective-C 2.0 Programming Guide.
How it works with an object depends on it's implementation of the NSFastEnumeration protocol. The NSDictionary class reference describes how it works with dictionaries:
On Mac OS X v10.5 and later, NSDictionary supports the NSFastEnumeration protocol. You can use the for…in construct to enumerate the keys of a dictionary, as illustrated in the following example.
I have a NSMutableArray:
NSMutableArray *temp = //get list from somewhere.
Now there is one method objectAtIndex which returns the object at specified index.
What I want to do is that, I want to first check whether an object at specified index exists or not. If it exists than I want to fetch that object. Something like:
if ([temp objectAtIndex:2] != nil)
{
//fetch the object
}
But I get exception at the if statement saying that index beyond bound.
Please anyone tell me how to achieve this.
you cannot have 'empty' slots in an NSArray. If [myArray count]==2 ie array has two elements then you know for sure that there is an object at index 0 and an object at index 1. This is always the case.
Check the length first using the count method.
if ([temp count] > indexIWantToFetch)
id object = [temp objectAtIndex:indexIWantToFetch];
you could do this way:
When you initialize, do something like:
NSMutableArray *YourObjectArray = [[NSMutableArray alloc] init];
for(int index = 0; index < desiredLength; index++)
{
[YourObjectArray addObject:[NSNull null]];
}
Then when you want to add but check if it already exists, do something like this:
YourObject *object = [YourObjectArray objectAtIndex:index];
if ((NSNull *) object == [NSNull null])
{
/// TODO get your object here..
[YourObjectArray replaceObjectAtIndex:index withObject:object];
}
Just check that the index is >= 0 and < count
Returns the number of objects currently in the receiver.
- (NSUInteger)count
int arrayEntryCount = [temp count];
First of all you check the length of array-
NSMutableArray *temp = //get list from somewhere.
now check-
if(temp length)
{
Your objectclass *obj = [temp objectAtIndex:indexnumber];
// indexnumber is 0,1,2 ,3 or anyone...
}