I'm new in Obj C programming, so i will start from beginning
I have an array with some NSNumber and NSString elements, i want to replace NSString elems to NSNumber elems. I decide to make this with for in construction get to new NSMutableArray all elements value and to NSMutableIndexSet their indexes, but when i made this i faced with trouble, here it is, i show you my code and log.
NSArray *oneMoreStack = [program copy];
NSLog(#" stack=%#",oneMoreStack);
NSLog(#" show me index ind=%#",[oneMoreStack indexOfObject:#"x"]);
NSMutableIndexSet *myVarIndexesSet;
NSMutableArray *myVarsArray;
for (id myVarConst in oneMoreStack) {
if([myVarConst isKindOfClass:[NSString class]])
{
if([myVarConst isEqualToString:#"x"]){
[myVarsArray addObject:myVarConst];
NSLog(#"obj x=%#",myVarConst);
[myVarIndexesSet addIndex:[oneMoreStack indexOfObject:myVarConst]];
NSLog(#"ind x=%#",[oneMoreStack indexOfObject:myVarConst]);
}
}
When i run it log show me this:
Calculator[6306:f803] stack=(
x,
2,
"+"
)
Calculator[6306:f803] show me index ind=(null)
Calculator[6306:f803] obj x=x
Calculator[6306:f803] ind x=(null)
then crash [NSMutableArray replaceObjectsAtIndexes:withObjects:]: index set cannot be nil
So, my question is why does [oneMoreStack indexOfObject:myVarConst] return null? How can i fix it? Thanks.
I don't mention this code before because think problem is in getting indexes.
after previous part of code goes this part:
[stack replaceObjectsAtIndexes:[myVarIndexesSet copy] withObjects:[myVarsArray copy]];
after that crash with error report i mention previously. Thanks.
[oneMoreStack indexOfObject:myVarConst] returns an NSUInteger, a primitive type, not an object.
In your NSLog, you are using %#, which says "Hey, take this object I'm passing as an argument, call -description on it, and print it out". Luckily, the NSUInteger you are passing in happens to be 0, NSLog thinks that it is a null object, and you aren't crashing. If the call to -indexOfObject: returns non-0, you will likely crash.
Try this instead:
// For iOS
NSLog(#" show me index ind=%u", [oneMoreStack indexOfObject:#"x"]);
or
// For 64-bit and 32-bit Mac OS X
NSLog(#" show me index ind=%lu", (unsigned long)[oneMoreStack indexOfObject:#"x"]);
You can learn more about string formats at:
Formatting String Objects
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 am quite new to objective-c and I am trying to convert an int into a NSNumber so that I can save it into Core-Data.
I've the following piece of code (index is an NSInteger)
- (void) associateOrNotToARoutine:(NSString*)exerciseName associate:(BOOL)associate index:(NSInteger)index
NSLog(#"number w index %d, %d",[NSNumber numberWithInteger:index],index);
and it returns
number w index 170413600, 2
I need an int of 2 to be translated into a number 2 along with all other numbers to be translated into the correct number... Could anyone tell me why i am getting this convertion? I tried reading on NSNumber manual but i found nothing
Try:
NSLog(#"number w index %#, %d",[NSNumber numberWithInteger:index],index);
^^
The %# format specifier will call the [NSNumber description] method, which should return the value you are after. Your original code will return the address of the NSNumber object, not its content.
Even though this question has already been answered, I thought I'd flesh out a longer answer for future readers in general:
What's happening?
%d is a C format string used to indicate one of the passed parameters is an integer (int) ivar value. Much like %f is used for float values.
[NSNumber numberWithInteger:index] returns a pointer to an NSNumber instance. If you use %d, NSLog thinks you're passing it an integer when, in fact, you're passing a pointer. So the pointer value (a memory address) is printed.
What's %#?
As mentioned by trojanfoe: %# tells NSLog() that you are passing an object. In that case, NSLog asks the object to describe itself using a string… it calls the description method.
Specific answer
For this specific question, there are multiple ways. The two main one being:
NSLog(#"number w index %#, %d", [NSNumber numberWithInteger:index], index);
NSLog(#"number w index %d, %d", [[NSNumber numberWithInteger:index] intValue], index);
Extra goodness
When using %#, the passed object can be anything that responds to description, essentially any descendant of NSObject. Also, if you're creating your own classes, it's a good idea to overload description to return a more meaningful string than the default NSObject implementation.
// Try using it with NSArray or NSDictionary and see how each describe themselves.
NSLog(#"the array description: %#", myArray);
NSLog(#"the dictionary description: %#", myDictionary);
You should use,
[[NSNumber numberWithInteger:index] intValue]
to get the integer value, the NSNumber, is holding
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);
I thought that I knew how to use fast enumeration, but there is something I don't understand about it. If I create three NSString objects and three NSNumber objects and put them in an NSMutableArray:
NSString *str1 = #"str1";
NSString *str2 = #"str2";
NSString *str3 = #"str3";
NSNumber *nb1 = [NSNumber numberWithInt:1];
NSNumber *nb2 = [NSNumber numberWithInt:2];
NSNumber *nb3 = [NSNumber numberWithInt:3];
NSArray *array = [[NSArray alloc] initWithObjects:str1, str2, str3, nb1, nb2, nb3, nil];
then I make do fast enumeration on all NSString objects, like this:
for (NSString *str in array) {
NSLog(#"str : %#", str);
}
In the console, I get this result :
2011-08-02 13:53:12.873 FastEnumeration[14172:b603] str : str1
2011-08-02 13:53:12.874 FastEnumeration[14172:b603] str : str2
2011-08-02 13:53:12.875 FastEnumeration[14172:b603] str : str3
2011-08-02 13:53:12.875 FastEnumeration[14172:b603] str : 1
2011-08-02 13:53:12.876 FastEnumeration[14172:b603] str : 2
2011-08-02 13:53:12.876 FastEnumeration[14172:b603] str : 3
I logged only the NSStrings, but I get a line for every object in the array, even the NSNumbers and I don't understand why. Does fast enumeration always use every object contained in an array?
When you write a forin loop like that, it casts every object in the array as an NSString, then prints them out as requested.
If you want only the NSStrings, you would need to write something like this:
for (id obj in array) {
if ([obj isKindOfClass:[NSString class]]) {
NSLog(#"str: %#", obj);
}
}
The for all loop doesn't know the difference between NSStrings and Integers -- it will simply go through the entire array, cast each as an NSString, and print them out as you asked.
I'm pretty sure that fast enumeration returns all objects in the array- all that you're doing in for (NSString *str in array) is typecasting str to an NSString. In the body of the loop you need to check the class of the returned object to make sure that it is an NSString.
for(NSString *str in array)
{
if([str isKindOfClass:[NSString class]])
NSLog(#"str : %#", str);
}
Objective-C is dynamically typed, meaning that at runtime (when the loop actually runs), objects are all effectively one type (id) with different classes. The language allows optional compile-time static typing, but all that does is check whether the messages you're sending are valid for the type you've marked. It doesn't actually change the behavior of your program. If you cast an object to be a different type than it actually is, all you're doing is lying to the compiler and defeating its type-checker.
Every object that descends from NSObject implements the method - (NSString)description, %# in Objective-C formate string will take the corresponding argument for the %# and call its description method, Most subclasses of NSObject will implement there own version of - (NSString)description. The same thing happens when you type
> po anObject
in the debugger.
for (NSString *str in array) {
is a way to enumerate through all the elements in array.
You expectative that by specifying NSString you get only the objects of that type is not correct. Rather, all the objects pointers are cast to that type (NSString*).
Have a look at Fast Enumeration in The Objective-C Programming Language guide.
I don't understand where is the unexpected behavior, using the enhanced for loop in an NSMutableArray will just iterate thru every single object in the array which in your case is 6, the result is correct and expected.
The numbers will just get casted to Strings.
in fast enumeration no typecasting,just assigning the pointer into new object
So, I'm struggling a bit with my programming project.
I have a object that stores player information, name, wins, losses.
I proceed to use that object in another object (a bracket) that sets the values of the player information, after each loop it copies the player object to a NSMutable in the bracket class.
Within the bracket class I have a method to print out the information, which was easy enough to figure out.
Now, to generate what will happen for the next bracket, I set up a method that will return a bracket when it's finished copying who won or lost.
I've done this all within the same bracket method so I could access the data as easily as possible. How do I simply just make a copy of the player object and add it to the new bracket?
I'm finding that I'm just getting garbage values or nothing at all when I try to print out the Bracket I've just generated. Here's my function that I'm having trouble with.
-(Bracket *) NextRound//Configures the next round
{
int i, y, *selection; //counter and selection
int comp;
y = 1;
i = 0;//so the counter won't get messed up
Bracket *roundx = [Bracket new]; //creates the bracket that will be sent back with the winners.
NSLog(#"Did %#(1) or %#(2) win (1 or 2)?: ",[[playerarray objectAtIndex:i] name], [[playerarray objectAtIndex:y] name]);
scanf("%d",&selection);
comp = selection++;
if (comp == 1)
{
NSLog(#"Player %d %# selected to win", i, [[playerarray objectAtIndex:i] name]);
[[self.playerarray objectAtIndex:i] setNext];//bool value for win or not
[roundx.playerarray addObject: [self.playerarray objectAtIndex:i]];
[roundx Print];//Too see if it has anything, usually it does not.
}
else
{
i++;
NSLog(#"Player %d %# selected to win", i, [[playerarray objectAtIndex:i] name]);
[[self.playerarray objectAtIndex:i] setNext];
[roundx.playerarray addObject: [self.playerarray objectAtIndex:i]];
[roundx Print];
}
return(roundx);
}
So, I thought that would just work. It compiles just fine (I get a few warnings, but it's about the integers and such that I use for logic mostly).
Thank You!
My comments:
The definition of selection is incorrect. You have defined it as a pointer to an int, but you are using it as if it were an int everywhere in your code. Note that selection++ increments selection by sizeof(int) not 1.
You shouldn't really be using -new to initialise objects but -alloc and then -init. (This is the modern convention).
The most likely cause of your problem is that playerarray is not initialised.