I am trying to remove objects at array starting at index 5 to the end of the list. I have a for loop to do this, however now I discovered
- (void)removeObject:(id)anObject inRange:(NSRange)aRange
The question is what is the anObject here? I only need range as far as I know
removeObject:inRange: deletes an object within a certain range. This method would be useful if you wanted delete the string #"Hello World" only if it is one of the first 5 elements.
It sounds like what you are trying to do is delete all objects after the 5th element. If that is what you are trying to do, you should use the removeObjectsInRange: method. For example:
NSRange r;
r.location = 5;
r.length = [someArray count]-5;
[someArray removeObjectsInRange:r];
You want
- (void)removeObjectsInRange:(NSRange)aRange
Removes from the array each of the objects within a given range.
Related
I have an array of objects. Each object has property "date" and "title".
I want to populate sectioned UITableView with those items like:
Section 1 - 2012.06.12 (taken from object.date)
Cell 1.1: Title 1 (taken from object.name)
Cell 1.2: Title 2
Cell 1.3: Title 3
...
Section 2 - 2012.06.13
Cell 2.1: Title 1
Cell 2.2: Title 2
..
Section 3 ..
I can do that by manually creating 1..n NSMutableArrays for all date combinations and filling them with object.name values. But the problem is I do not know how many date combinations there are, so it should be done dynamically. Also, the date property can repeat in different objects
My object structure is:
Object
-NSDate - date
-NSString - title
UPD:
I was thinking if it is possible to create NSDictionary, where the key would be my date and the object would be NSArray, which contains all my items for the key-date. But I do not know how to do that dynamically.
I hope I explained my question clearly enough.
Thank you in advance!
You can create arrays based on date.You have array of objects, so iterate through this array of objects to get distinct dates, as follows:
for(int i =0;i<[objectsArr count];i++)
{
if(![newDateArr containsObject:[objectsArr objectAtIndex:i].date])
{
[newDateArr addObject:[objectsArr objectAtIndex:i].date];
}
NSMutableArray *newTitleArray = [newTitleDictionary objectForKey:#"[objectsArr objectAtIndex:i].date"];
if(newTitleArray != nil)
{
[newTitleArray addObject:[objectsArr objectAtIndex:i].title];
}
else
{
newTitleArray = [[[NSMutableArray alloc] init] autorelease];
[newTitleArray addObject:[objectsArr objectAtIndex:i].title];
}
[newTitleDictionary setValue:newTitleArray forKey:#"[objectsArr objectAtIndex:i].date"];
}
where newTitleDictionary and newDateArr are declare outside this method.Now you can use both is newTitleDictionary and newDateArr to populate tableview.
If I understand you correctly, you want to put an object into an array and then use that array to populate a table view?
Just add the date object each time to the NSMutableArray.
[myArray addObject:dateObject];
Then when it comes to populating the table view..
DateObject *newDateObj = [myArray objectAtIndex:index];
I hope this helps and I understood your question
EDIT To answer now I understand a bit more.
Step 1
Check through the existing array of dates and see if there are any that match maybe by iterating through it using a for loop. Search online for how to compare NSDate.
Step 2 If it doesn't match any then insert it into the array as an array with just that date on it's own so the array count will be one. If it does match then insert it into the array along with that one making the array count 2 or more.
Step 3 When it comes to declaring the section amount for the table just return the dateHolderArray count.
Step 4 When declaring the amount of rows in each section, return the array count for the array thats inside the dateHolderArray.
Step 5 Display the content when it comes to populating the cells with information. It becomes just a task of getting the dates from the arrays using the section ids and row ids.
This is how I would do it, there are probably many other methods. Any questions just ask
I'm adding an object to a NSMutableArray like this:
[array addObject:myObject];
I now want to send a reference to my delegates of the Array Index where this object was added.
Is there an easy way to find out the index where my object was added in the array so that later I can call
[array objectAtIndex:index]
to get a reference back for it?
Thanks!
Rather than passing the index of an object (which could be incorrect) to your delegate, pass a reference to the object itself. If the delegate needs the index of the object in the array, it can figure it out itself using -indexOfObject: as Antonio MG describes. The index of any given object in a mutable array can change as objects are added, inserted, and deleted. Counting on indices to remain valid over any period of time is like leaving a jelly sandwich on the counter -- it's sure to attract bugs.
You need to serialize access to a mutable array and -addObject: always adds the object to the end of the array. Given those two assertions, you know the index of the next added object will always be the current length of the array. So the following will hold true:
NSUInteger nextIndex = [array count];
[array addObject:myObject];
// you can now tell your delegates that nextIndex is the index of myObject
Use this method for that:
index = [animalOptions indexOfObject:myObject];
The latest added object should be at [array count] - 1 index. You can always rely on "count - 1" scheme to determine the last index.
If you call addObject you always add the object at the end (so count - 1).
You can use "insertObject:atIndex:" to specify an index.
For your question: indexOfObject:
Direct after adding the object's index is array.count -1 .
I am working on a small isometric engine for my next iPhone game. To store the map cells or tiles I need a 2 dimensionel array. Right now I am faking it with a 1-dimensionel, and it is not good enough anymore.
So from what I have found out looking around the net is that in objective-c I need to make an array of arrays.
So here is my question: How do I dynamicly create arrays at runtime based on how many map-rows I need?
The first array is easy enough:
NSMutableArray *OuterArray = [NSMutableArray arrayWithCapacity:mapSize];
now I have the first array that should contain an array for each row needed.
Problem is, it can be 10 but it can also be 200 or even more. So I dont want to manually create each array and then add it. I am thinking there must be a way to create all these arrays at runtime based on input, such as the chosen mapsize.
Hope you can help me
Thanks in advance
Peter
I think this previous question should help.
2d arrays in objective c
Nothing to do with me. I have never owned an iphone or tried to write code for one.
The whole point of NSMutableArray is that you don't care. Initialize both dimensions with an approximate size and then add to them. If your array grows beyond your initial estimate the backing storage will be increased to accomodate it. This counts for both your columns (first order array), and rows (second order array).
EDIT
Not sure what you meant in your comment. But this is one way to dynamically create a 2-dimensional mutable array in Objective-C.
NSUInteger columns = 25 ; // or some random, runtime number
NSUInteger rows = 50; // once again, some random, runtime number
NSMutableArray * outer = [NSMutableArray arrayWithCapacity: rows];
for(NSUInteger i; i < rows; i++) {
NSMutableArray * inner = [NSMutableArray arrayWithCapacity: columns];
[outer addObject: inner];
}
// Do something with outer array here
NSMutableArray can hold as many elements as you want to add to it. (Based on available heap though).
All you have to do is when you want to add an element(Array) to this mutable array you can add it using the addObject method.
So you create a MutableArray as follows:
NSMutabaleArray *outerArray = [NSMutableArray array]; // initially contains 0 elements.
[outerArray addobject:<anotherArray>];
From your rejection of the other answers I think you don't know how to add them in a loop, or am I wrong?
Try:
for (i = 0; i < mapSize; i++)
[outerArray addObject: [[NSMutableArray alloc] init]];
or, if you know or can estimate the size of the second dimension:
for (i = 0; i < mapSize; i++)
[outerArray addObject: [[NSMutableArray alloc]
initWithCapacity: your_2nd_d_size]];
Now, how you fill the arrays, i.e. where you get the contents depends on you. In one or more loops, you do:
[(NSMutableArray *)[outerArray objectAtIndex: i]
addObject: your_current_object];
I'm sure this is a very obvious question but I'm not getting anywhere with it and I've been trying for half an hour or so now.
I have an NSMutableDictionary which has keys & values, obviously. Each key stores an array of objects. What I need to do is find a specific array in a key and get the list of the array. The catch is that I don't know the value of the key, I just know it's index. (EG: I know I need to find the array in the 2nd key).
I am almost certain this is a very easy & trivial thing to do but it's escaping me, I've only been doing Obj-C for a short while so not entirely at home with it yet!
Thanks,
Jack.
Use allKeys: to access the keys of your dictionary.
- (NSArray *)allKeys
Use as below .
NSArray* dictAllKeys = [dict allKeys];
if([dictAllKeys count] > 2)
{
NSArray* myArrayInDict = [dict objectForKey:[dictAllKeys objectAtIndex:1]];
// get the length of array in dict at 2nd key
int length = [myArrayInDict count];
}
The order will probably change if another key/value pair is added, it is a NSMutableDictionary. It is best not to rely on the order of a NSDictionary or NSSet.
Suggestion: Either use another container that does provide ordering such as NSMutableArray or find the item using the dictionary's value arrays, perhaps with NSPredicate.
My aim is to produce an array, which I can use to add section headers for a UITableView. I think the easiest way to do this, is to produce a sections array.
I want to create section headers for dates, where I'll have several or no rows for each.
So in my populate data array function, I want to populate a display array. So record 1, look for the first date in my display array, create a new array item if it doesn't exist, if it does exist add 1 to the count.
So I should end up with something like this.
arrDisplay(0).description = 1/June/2001; arrDisplay(0).value = 3;
arrDisplay(1).description = 2/June/2001; arrDisplay(1).value = 0;
arrDisplay(2).description = 3/June/2001; arrDisplay(2).value = 1;
arrDisplay(3).description = 5/June/2001; arrDisplay(3).value = 6;
My question is how do I create and use such an array with values, where I can add new elements of add to the count of existing elements and search for existing elements ?
I think, if i understand you, an NSMutableDictionary would work. (as NR4TR said) but, i think the object would be the description and the key would be the count. you could check for the key and get the count in the same gesture. if the return value of objectForKey is nil, it doesn't exist.
NSMutableDictionary *tableDictionary = [[NSMutableDictionary alloc] init];
NSString *displayKey = #"1/June/2001";
NSNumber *displayCount = [tableDictionary objectForKey:displayKey];
if (displayCount != nil) {
NSNumber *incrementedCount = [[NSNumber alloc] initWithInteger:[displayCount integerValue] + 1];
[tableDictionary removeObjectForKey:displayKey];
[tableDictionary setValue:incrementedCount
forKey:displayKey];
[incrementedCount release];
}
else {
NSNumber *initialCount = [[NSNumber alloc] initWithInteger:1];
[tableDictionary setValue:initialCount
forKey:displayKey];
[initialCount release];
}
EDIT: Hopefully this isn't pedantic, but I think a couple pointers will help.
Dictionaries, Sets, and Arrays all hold objects for retrieval. The manner of holding and retrieval desired drives the decision. I think of it based on the question 'what is the nature of the information that I have when I need an object being held?'
NSDictionary and NSMutableDictionary
Hold n objects per key. (I think...I haven't had to test a limit, but i know you can get an NSSet back as a value.)
KEY is more important than INDEX. I don't think of dictionaries as ordered. they know something and you need to ask the correct question.
NSArray and NSMutableArray
hold n objects in order.
INDEX is most important bit of information. (you can ask for the index of an object but, even here, the index is the important part)
you will typically drive table views with an array because the ordered nature of the array fits.
NSSet, NSMutableSet, and NSCountedSet
A collection of objects without order.
You can change any of these into the other with something like [nsset setFromArray:myArray];
and all of these things can hold the other as objects. I think an array as your top level is the correct thinking, but beyond that, it becomes an issue of implementation
Try array of dictionaries. Each dictionary contains two objects - section title and array of section rows.
If you want to have a description AND a rowcount then you can either create a class with those two properties and generate an NSArray of objects with that class or instead of all that you can just use an NSDictionary to store key/value lookups.
I think NSCountedSet is closest to what you want. It doesn't have an intrinsic order, but you can get an array out of it by providing a sort order.