working with a basic objective c example here, tried to use replaceObjectAtIndex for an array and it doesn't seem to be working.
my code:
NSMutableArray *myArray=[NSMutableArray array];
[myArray addObject:#"First string"];
[myArray addObject:#"Second string"];
[myArray addObject:#"Third string"];
NSString *newElement=[myArray objectAtIndex:1];
NSLog(#"New object at index 1 BEFORE is %#", newElement);
[myArray replaceObjectAtIndex:1 withObject:#"Hello"];
NSLog(#"New object at index 1 AFTER is %#", newElement);
theoretically the output for newElement should now display "Hello", but it's still displaying "Second String"
output:
2012-05-30 11:21:16.638 cocoa lab[753:403] New object at index 1 BEFORE is Second string
2012-05-30 11:21:16.641 cocoa lab[753:403] New object at index 1 AFTER is Second string
please advise
thank you
You need to get the new value from the array after replacing it
// ...
[myArray replaceObjectAtIndex:1 withObject:#"Hello"];
/* ADD THIS */
newElement=[myArray objectAtIndex:1];
NSLog(#"New object at index 1 AFTER is %#", newElement);
At the moment you fetch the original string, replace the array's object, and print out the original string again.
You need to reset the value of newElement after calling replaceObjectAtIndex:, so add another line before logging the value the second time:
newElement=[myArray objectAtIndex:1];
UPDATE 1
And don't feel bad -- we've all done this to ourselves at one time or another. :-)
UPDATE 2
By the way, a good way to avoid this kind of problem in general is to get in the habit of using separate local variables in these kinds of situations, for example, you could rewrite the code you posted as follows:
NSString *initialValue = [myArray objectAtIndex:1];
NSLog(#"New object at index 1 BEFORE is %#", initialValue);
[myArray replaceObjectAtIndex:1 withObject:#"Hello"];
NSString *newValue = [myArray objectAtIndex:1];
NSLog(#"New object at index 1 AFTER is %#", newValue);
Related
I have this snipped of code that results in an array with a whole bunch of "<null>" throughout and I need to figure out how to remove them. Obviously after smashing my head against the keyboard I'm asking for some help.
In my .h I have declared:
NSArray *sortedContacts;
NSArray *rawContacts;
And then in .m:
-(void) buildContacts {
ABAddressBook *addressBook = [ABAddressBook sharedAddressBook];
NSArray *contacts = [addressBook people];
rawContacts=contacts;
NSArray *firstNames = [rawContacts valueForKey:#"First"];
NSArray *lastNames = [rawContacts valueForKey:#"Last"];
NSArray *organization = [rawContacts valueForKey:#"Organization"];
NSMutableArray *fullNames = [NSMutableArray array];
for(int i = 0; i < [firstNames count]; i++)
{
NSString *fullName = [NSString stringWithFormat:#"%# %# %#",
[firstNames objectAtIndex:i],
[lastNames objectAtIndex:i],
[organization objectAtIndex:i]];
[fullNames addObject:fullName];
}
NSMutableArray *fullList = [[NSMutableArray alloc]initWithArray:fullNames];
[fullList removeObjectIdenticalTo: #"<null>"];
sortedContacts = [fullList sortedArrayUsingSelector:#selector(compare:)];
NSLog(#"%#",sortedContacts);
}
I've tried so many things that I just can't see the forest for the trees anymore.
The text <null> is how the singleton instance of NSNull describes itself. That is, it's what -[NSNull description] returns.
In turn, these NSNull objects are getting into your firstNames, lastNames, and organization arrays because that's what Key-Value Coding does when you call -valueForKey: on an array and some of the elements return nil when that message is forwarded on to them with the same key. That is, calling [rawContacts valueForKey:#"First"] causes NSArray to call [element valueForKey:#"First"] for each element in rawContacts and to put the result in the array it builds. But, since an array can't contain nil, if one of those elements returns nil from [element valueForKey:#"First"], an NSNull object is added in its place.
Then, you are formatting the string fullName from the corresponding elements of firstNames, lastNames, and organization. You need to check if any of those elements are NSNull using if ([value isKindOfClass:[NSNull class]]) and handling that. For instance, you might just skip that record. Or you might combine the available fields and leave out any unavailable ones.
In any case, none of the elements of fullList will be #"<null>" because formatting values into #"%# %# %#" can never result in that string. (It might be #"<null> <null> <null>" or something like that, but never just #"<null>".)
A quick look at your code suggests you cannot get any empty strings added to your array, (a) you add elements using:
[fullNames addObject:fullName];
and fullName is created using:
[NSString stringWithFormat:#"%# %# %#" ...
so even if the %#'s get replaced by nothing you'll still have 2 spaces...
Maybe this is why all the things you've tried fail, if you're looking for empty strings you won't find them.
(Addendum: Question now says you're looking for #"<null>", you won't get that either for the same reason - there is at least two spaces in your string.)
The simple answer to removing invalid entries in fullNames is not to add them in the first place. You are adding elements in a loop (for), and conditional logic (e.g. if) inside the loop to determine whether you have something valid to add - however you define "something valid" - and only add an item to fullNames if so.
HTH
I'm not really familiar with the AddressBook framework, however this might be what's causing the confusion:
The values you collect in your arrays firstNames, lastNames and organization can be of type NSString or NSNull. You have to do any null-checking within the for-loop, before the fullName-string is constructed.
Remove this useless line:
[fullList removeObjectIdenticalTo: #"<null>"];
And replace the contents of your for-loop with the following code:
for(int i = 0; i < [firstNames count]; i++)
{
NSString *firstName = [firstNames objectAtIndex:i];
NSString *lastName = [lastNames objectAtIndex:i];
NSString *org = [organization objectAtIndex:i];
NSMutableArray *namesArray = [NSMutableArray array];
if ([firstName isKindOfClass:[NSString class]])
[namesArray addObject:firstName];
if ([lastName isKindOfClass:[NSString class]])
[namesArray addObject:lastName];
if ([org isKindOfClass:[NSString class]])
[namesArray addObject:org];
if (namesArray.count > 0)
[fullNames addObject:[namesArray componentsJoinedByString:#" "]];
}
I have a mutable array of checked box
NSMutableArray *arrayOfCheckedBox = [NSMutableArray arrayWithObjects:namePropertyString, lastNamePropertyString, companyPropertyString, workEmailPropertyString, personalEmailPropertyString, workPhonePropertyString, cellNumberPropertyString, nil];
[arrayOfCheckedBox removeObjectIdenticalTo:[NSNull null]]; //not working
NSLog(#"array of check box = %#", arrayOfCheckedBox);
If I click on check boxes at index 0, 1 and 4, it will only collect object at indexes 0 and 1 only and will not detect index 4 at all.
I get the values at the selected index in log before getting it in arrayOfCheckedBox. How to get checked values in this case?
The problem is that you're hitting a nil value, so the arrayWithObjects: method thinks you're at the end of the list of objects.
Something like this will work:
NSMutableArray *arrayOfCheckedBox = [NSMutableArray arrayWithCapacity:7];
if (namePropertyString)
[arrayOfCheckedBox addObject:namePropertyString];
if (lastNamePropertyString)
[arrayOfCheckedBox addObject:lastNamePropertyString];
I would suggest storing the check box values in an array of BOOLs.
Wrap them in NSNumbers first and unwrap them to retrieve them.
Wrap to store,
[NSNumber numberWithBool:YES]]
Unwrap to retrieve,
[[your_array objectAtIndex:index] boolValue]
For null values appear to be string literals #"" rather than the NSNull.So use following way to remove null object :
NSLog(#"%d", [arrayOfCheckedBox count]);
NSString *nullString = #"<null>";
[arrayOfCheckedBox removeObject:nullString];
NSLog(#"%d", [arrayOfCheckedBox count]);
I get an array from a JSON and I parse it into an NSMutableArray (this part is correct and working). I now want to take that array and print the first object to a Label. Here is my code:
NSDictionary *title = [[dictionary objectForKey:#"title"] objectAtIndex:2];
arrayLabel = [title objectForKey:#"label"];
NSLog(#"arrayLabel = %#", arrayLabel); // Returns correct
//Here is where I need help
string = [arrayLabel objectAtIndex:1]; //I do not get the first label (App crashes)
NSLog(#"string = %#", string);
other things that I have already tried are as follows:
string = [NSString stringWithFormat:#"%#", [arrayImage objectAtIndex:1]];
and
string = [[NSString alloc] initWithFormat:#"%#", [arrayImage objectAtIndex:1]];
Any help is greatly appriciated!
EDIT: The app does not return a single value and crashes.
Your code doesn't match the structure of your JSON. In your comment on the deleted answer, you said you got an exception when sending objectAtIndex: to an NSString. In your case, arrayLabel isn't an array when you think it is.
If your JSON has an object, your code needs to treat it as an NSDictionary. Likewise for arrays and NSArray and strings and NSString.
In addition to whatever else was going on, you repeatedly refer to "first" but use the index 1. In most C-based programming languages (and others, as well) the convention is that indexes into arrays are 0-based. So, use index 0 to get the first element.
Here I am getting the cityName1 with the city names like Piscataway, Iselin, Broklyn etc fetched from the tgpList1 array and I need to put the values into an array called item5.
There are 133 records fetched by the above iteration. The following code stores only the last record's cityName1 and not the entire list of city names though inside the loop.
I tried many ways but I am missing something.
tgpList1 is an array.
tgpDAO is an NSObject with two objects NSString *airportCode and NSString *cityName
NSArray *item5 = [[NSArray alloc]init];
for (int currentIndex=0; currentIndex<[tgpList1 count]; currentIndex++)
{
tgpDAO *tgpTable = (tgpDAO *)[self.tgpList1 objectAtIndex:currentIndex];
NSLog(#"The array values are %#",tgpList1);
NSString *cityName1 = tgpTable.cityName;
item5 =[NSArray arrayWithObjects:cityName1, nil];
}
Use mutable array.
{
NSMutableArray *item5 = [[NSMutableArray alloc]initWithArray:nil];
for (int currentIndex=0; currentIndex<[tgpList1 count]; currentIndex++) {
tgpDAO *tgpTable = (tgpDAO *)[self.tgpList1 objectAtIndex:currentIndex];
NSLog(#"The array values are %#",tgpList1);
NSString *cityName1 = tgpTable.cityName;
[item5 addObject:cityName1];
}
}
Instead of
item5 =[NSArray arrayWithObjects:cityName1, nil];
use
[item5 addObject:cityName1];
There are more ways of achieving that. However, this is the one that is designed for that purpose and the most "readable" from my pont of view.
If you need to clear the contents of item5 before then call
[item5 removeAllObjects];
right before the for loop.
What you were doing: arrayWithObjects allways creates a new array that ist made of the objects that are passed to it as aguments. If you do not use ARC, then you would create some serious memory leak with your code because arrayWithObjects creates and retains an object on every loop and on the next loop all references to the array object, that was just created, are lost without being released. If you do ARC then you do not have to worry about in this case.
NSMutableArray *myCities = [NSMutableArray arrayWithCapacity:2]; // will grow if needed.
for( some loop conditions )
{
NSString* someCity = getCity();
[myCities addObject:someCity];
}
NSLog(#"number of cities in array: %#",[myCities count]);
I have an array which has several objects (all of different classes) in it. But using enumeration doesn't work on it for some reason.
NSString *arrayString;
NSURL *arrayUrl;
NSProcessInfo *arrayPr;
NSDictionary *arrayDictionary;
NSMutableString *arrayMString;
NSMutableArray *objectArray = [NSMutableArray arrayWithObjects:arrayString,arrayUrl,arrayPr,arrayDictionary,arrayMString,nil];
for( NSString *item in objectArray ){
NSLog(#"Class name is: %#", [item className]);
}
I think it might be something to do with how the objects are been added to the array but i'm new to objective-c and not sure.
you aren't actually populating the array.
NSString *arrayString;
declares a variable, arrayString, of type NSString. it's not initialized (so it deserves to crash when you use the variable -- but may be 0 with some build settings).
so, to assign a variable:
NSString *arrayString = [NSString stringWithFormat:#"sksjdhf %f\n", 3.3];
arrayWithObjects adds objects from the (va list) argument until nil/null/0 is encountered.
you must set up the remainder of your variables/arguments correctly before using them.
this should work as you expect it to:
NSString * str = #"a string";
NSMutableArray *objectArray = [NSMutableArray arrayWithObjects:str, nil];
for (NSObject * item in objectArray) {
NSLog(#"Class name is: %#", [item className]);
}
In the for loop, use an id data type. The id data type is a general purpose data type that can be used to store a reference to any object.
For example:
for ( id item in objectArray ) {
NSLog(#"Class name is: %#", [item className]);
}
Yep, that's how you do it. If you're having trouble, it is not in the enumeration syntax itself.