i am wondering how its possible to add an index for a tableview to an array. i am trying to save this index to the array in order to be able to view it later. i just am interested in knowing how to save the index to the array. thanks
Use a NSMutableArray and send it an addObject: message with the NSIndexPath as an argument.
Same way you save anything to an array:
NSMutableArray *myArray = [NSMutableArray array];
[myArray addObject:myIndexPath];
Related
How can I add object at specified index?
in my problem
NSMutableArray *substring
contains index and object alternatively
and I need to add it to the another array str according to index I getting from this array.
NSMutableArray *str=[NSMutableArray new];
if ([substrings containsObject:#"Category-Sequence:"])
{
NSString *index=[substrings objectAtIndex:5];
//[substrings objectAtIndex:5]
gives me integer position at which I need to add object in `str` array,
gives 5,4,8,2,7,1 etc
NSString *object=[substrings objectAtIndex:1];
//[substrings objectAtIndex:1] gives object,gives NSString type of object
[str insertObject:object atIndex:(index.intValue)];
}
please suggest some way to achieve it.
Thanks in advance!
Allocate the array first & then try to add objects in it.
NSMutableArray *str = [[NSMutableArray alloc]init];
if ([substrings containsObject:#"Category-Sequence:"])
{
NSString *index=[substrings objectAtIndex:5];
NSString *object=[substrings objectAtIndex:1];
[str insertObject:object atIndex:(index.intValue)];
}
Allocate the NSMutableArray before inserting objects into it:
NSMutableArray *strMutableArray = [[NSMutableArray alloc] init];
(You’ll also need to release it when you’re done if you’re not using ARC.)
Or you could also use a temporary object, if you don’t need to keep strMutableArray:
NSMutableArray *strMutableArray = [NSMutableArray array];
Then you can insert objects into the NSMutableArray.
Be careful with using indexes of and in different arrays, however. There might be a better way to do what you want.
I know how I would achieve this using NSMutableArray, but whats the correct way of emptying a whole array of class NSArray. I need to do this because I need to reload a tableView. Im using ARC.
NSArray is an immutable type. You cannot alter it's contents after creation.
Either use an NSMutableArray or replace it with a new (empty) NSArray.
NSArray *yourArray = [ whatever objects you have ]
//to empty this array
yourArray = [NSArray array];
NSArray is an immutable (unchangeable) class so there is no way to remove elements from the array. Basically, you will have to throw the array away and replace it with a new NSArray. Alternatively, you could just use an NSMutableArray.
You cant empty a non mutable NSArray, the best approach is to get a mutable copy of your array:
NSMutableArray *arr=[yourArr mutableCopy];
[arr removeAllObjects];
I have array of strings
NSMutableArray * nam = [[NSMutableArray alloc] initWithObjects:#"ZAZ", #"London", #"Australia",#"England", #"Dallas", #"Mexico", #"Russia", nil];
How I can create indexed TableView from this string alphabetically??? Like in "Contacts"! Or maybe somebody know some lessons with this problem?
Edit : Create UITableView follow link. Use newArray as tableview array
Sort your NSMutableArray alphabetically like this:
NSMutableArray *newArray = [nam sortUsingSelector:#selector(localizedCaseInsensitiveCompare:)];
Use this newArray as TableViewDataSource array for alphabetically ordered cells
I have a NSMutableArray (tripHistory) that gets a NSMutableDictionary (currentUpdate) added to it every second with new data.
[currentUpdate setObject:testVariable forKey:#"Test"];
[tripHistory addObject:currentUpdate];
[currentUpdate removeAllObjects];
Yet when I loop through tripHistory calling [[tripHistory objectAtIndex:i] description] everything is null.
My loop is as follows:
for (int i=0; i<[tripHistory count]; i++)
{
NSLog(#"%#", [[tripHistory objectAtIndex:i] description]);
}
To initialize my variables, the following code is called only for the first update.
tripHistory = [[NSMutableArray alloc] init];
currentUpdate = [[NSMutableDictionary alloc] init];
Any ideas?
Adding an object to an NSArray doesn't make a copy of it. All that happens is its reference count is incremented. Therefore currentUpdate and the NSDictionary added to tripHistory are one-and-the-same. If you remove objects from currentUpdate you are also removing objects from the NSDictionary in tripHistory.
After adding currentUpdate to tripHistory all you need to do is release currentUpdate and start again with a new empty NSDictionary for the next update.
Do not remove objects. Dictionary and array are keeping references to the same objects. If you want to add another dict to array then release first dict and create a new one
You are removing all of the contents of the dictionary. Adding the dictionary to your array doesn't make a copy: The array will retain a reference to the dictionary, which you proceed to empty out each time you add something to it.
You should allocate a new dictionary each time through the loop and then add that dictionary o the array. If you are not using garbage collection or ARC you should also release the dictionary after it is added to the array.
i wanted to know how to add strings into an array.
I used the following methods but it is showing null.
1) [arrData addObject:[NSString stringWithString:strlast]];
2) [arrData addObject:strlast];
Thanks in advance
You can't add anything to an NSArray once it's created. You need to use an NSMutableArray if you want to make changes to it.
Update: You may actually have two problems.
Using an NSArray instead of an NSMutableArray when mutability is needed.
Not initializing the array object (either kind). If arrData is nil, you can happily send as many messages as you want to nil. Nothing will happen.
If it is showing null (nil) you need to make sure you set arrData somewhere in your code before trying to addObject:.
arrData = [[NSMutableArray alloc] init];
Also strlast is a string so use your second example, the first example is pointless.
[arrData addObject:strlast];
Did you allocate an array and assign it to arrData?
Try:
NSMutableArray *arrData = [NSMutableArray array];
NSString *string = #"My string";
[arrData addObject:string];
NSLog(#"%#", [arrData objectAtIndex:0]); //logs "My string"
If you're using a non-mutable array, you can also use arrayByAddingObject:
arrData = [arrData arrayByAddingObject: strlast];
but a mutable array is probably a better idea.