i am trying to get index of an array through indexOfObject method as follows but when i try to log the value to test the index i get a garbage value.. for testing purposes i am having an array with values {57,56,58..} to get an index of lets say 56,
NSNumber *num = [NSNumber numberWithInteger:56];
NSInteger Aindex = [myArray indexOfObject:num];
NSLog(#" %d",Aindex);
the value i get is something like 2323421. what am i possibly doing wrong??
The index returned by indexOfObject will be the first index for an occurence of your object. Equality is tested using isEqual method.
The garbage value you get is probably equal to NSNotFound.
Try testing anIndex against it. The number you are looking for isn't probably in your array :
NSNumber *num=[NSNumber numberWithInteger:56];
NSInteger anIndex=[myArray indexOfObject:num];
if(NSNotFound == anIndex) {
NSLog(#"not found");
}
or log the content of the array to be sure :
NSLog(#"%#", myArray);
Folks,
When an object is not found in the array the indexOfObject method does NOT return a 'garbage' value. Many systems return an index of -1 if the item is not found.
However, on IOS - because the indexOfObject returns an UNSIGNED int (aka NSUInteger) the returned index must be greater than or equal to zero. Since 'zero' is a valid index there is no way to indicate to the caller that the object was not found -- except by returning an agreed upon constant value that we all can test upon. This constant agreed upon value is called NSNotFound.
The method:
- (NSUInteger)indexOfObject:(id)anObject;
will return NSNotFound if the object was not in the array. NSNotFound is a very large POSITIVE integer (usually 1 minus the maximum int on the platform).
NSNumber *num1 = [NSNumber numberWithInt:56];
NSNumber *num2 = [NSNumber numberWithInt:57];
NSNumber *num3 = [NSNumber numberWithInt:58];
NSMutableArray *myArray = [NSMutableArray arrayWithObjects:num1,num2,num3,nil];
NSNumber *num=[NSNumber numberWithInteger:58];
NSInteger Aindex=[myArray indexOfObject:num];
NSLog(#" %d",Aindex);
Its giving the correct output, may be u have done something wrong with storing objects in ur array.
Try this:
NSArray's indexOfObject: method. Such as the following:
NSUInteger fooIndex = [someArray indexOfObject: someObject];
If you're using Swift and optionals make sure they are unwrapped. You cannot search the index of objects that are optionals.
I just checked. Its working fine for me. Check if your array has the particular number. It will return such garbage values if element is not present.
indexOfObject methord will get the index of the corresponding string in that array if the string is like #"Test" and you find like #"TEST" Now this will retun an index like a long number
Related
I have an array with 10 items. When I call "IndexOfObject" for the elements number 9 and the element number 10 Xcode return an exception: "NSRangeException"
reason: '_[_NSCFArray objectAtIndex:] index:2147483647 beyond
bounds(10)'.
From a previous NSLog, I saw that the two elements exist in the array but indexOfObject not find them. Why?
My code is:
NSDictionary * headConfig =[avatarDictionaryToSave objectForKey:#"head_dictionary"];
NSString * headImage =[headConfig objectForKey:#"layer_key"];
NSString * pathFace =[[NSBundle mainBundle]pathForResource:#"Face" ofType:#"plist"];
NSLog(#"%#", headImage);
NSArray *arrayFace =[NSArray arrayWithContentsOfFile:pathFace];
NSLog(#"the elements are: %#", arrayFace);//here headImage is present
int index =[arrayFace indexOfObject:headImage];
NSLog(#"the index is %d", index);
indexOfObject: returns NSNotFound when the object is not present in the array. NSNotFound is defined as NSIntegerMax (== 2147483647 on iOS 32 bit).
So it seems that the object you are looking for is just not there.
Please change the coding of adding the array values as I mentioned below.
// [arr_values addObject:[dictionary valueForKey:#"Name"]];
[arr_values addObject:[NSString stringWithFormat:#"%#",[dictionary valueForKey:#"Name"]]];
When target array elements are not in string format then while we using the
indexOfObject then that value can't able to find in the target array. So please try to
change the value of object as mentioned above while adding into array.
By default, an integer is assumed to be signed.
In other words the compiler assumes that an integer variable will be called upon to store either a negative or positive number. This limits the extent that the range can reach in either direction.
For example, a 32-bit int has a range of 4,294,967,295. In practice, because the value could be positive or negative the range is actually −2,147,483,648 to +2,147,483,647.
If we know that a variable will never be called upon to store a negative value, we can declare it as unsigned, thereby extending the (positive) range to 0 to +4,294,967,295.
An unsigned int is specified as follows:
unsigned int myint;
Something weird just happened.
I stored a NSNumber with an unsigned long long value in NSUserDefaults. When I retrieve it, the value just changed. It seems that system thinks the number is long long instead of unsigned long long.
What's worse is that when I compare the number retrieved from UserDefaults with the original number, the result is NotEqual!
what's wrong with the code? Thank you!
static NSString * const NumberKey = #"MyNumber";
unsigned long long value = 15908045869032883218ULL;
if ([[NSUserDefaults standardUserDefaults] objectForKey:NumberKey] == nil) {
NSNumber *number = [NSNumber numberWithUnsignedLongLong:value];
[[NSUserDefaults standardUserDefaults] setObject:number forKey:NumberKey];
NSLog(#"Original Number:%#", number); // 15908045869032883218, right
}
NSNumber *number = [[NSUserDefaults standardUserDefaults] objectForKey:NumberKey];
NSLog(#"Current Number:%#", number); // -2538698204676668398, weird
NSLog(#"Current Value:%llu", [number unsignedLongLongValue]); // 15908045869032883218, right
NSLog(#"%d", [number isEqualToNumber:[NSNumber numberWithUnsignedLongLong:value]]); // 0
NSLog(#"%d", [number unsignedLongLongValue] == value); // 1
To further answer your question. If you look in the documentation for NSNumber's isEqualToNumber: function you will notice the following line,
Two NSNumber objects are considered equal if they have the same id values or if they have equivalent values
it's important you understand this. In your code you are asking is my NSNumber object "number" equal to "value", you are not asking does the numerical value stored within my NSNumber object "number" equal the numerical value stored within my NSNumber object "value".
The last line of code you have written shows that in fact your NSNumber's numerical values are in fact equal.
NSLog(#"%d", [number unsignedLongLongValue] == value); //1
So you are correctly storing and retrieving the values, you should be using the == comparison method with NSNumber objects stored numerical values (ie intValue == intValue, unsignedLongLongValue == unsignedLongLongValue) and not comparing their object id's together.
As for this line of code
NSLog(#"Current Number:%#", number); // -2538698204676668398, weird
This is not weird, this is perfectly normal, as you have told NSLog to print out an NSObject representation of 'number'. I'm not 100% certain but I believe that NSNumber's - ( NSString * ) description function defaults to return an unsigned int value for the numerical value it contains. This is why you are getting the large negative number returned. You may want to look at NSNumber's - (NSString *)descriptionWithLocale:(id)aLocale function to print out the data in a more logical for for you, or you could use
NSLog(#"Current Number:%llu", [number unsignedLongLongValue]);
Which will give you the right answer.
EDIT:
Further to this, after looking into the issue what is happening is that on recollection of your NSNumber object from UserDefaults it's original number type is not being preserved (this information is highlighted in the documentation for NSNumber in the overview section)
(Note that number objects do not necessarily preserve the type they are created with.)
You can see this yourself if you log the following after retrieving "number" from user defaults (add this to the end of the code you have in your question) and have a look at the encoding values shown here
NSLog(#"%s", [number objCType]); //This will log out q
NSLog(#"%s", [[NSNumber numberWithUnsignedLongLong:value] objCType]); //this will log out Q
The difference between Q and q is that Q is an unsigned value... hence why you are having issues with the isEqualToNumber: function as the number types are different.
If you are so dead set on using the iSEqualToNumber: function to compare values then you could implement this to retrieve your value from NSUserDefaults.
NSNumber *number = [NSNumber numberWithUnsignedLongLong:[[NSUserDefaults standardUserDefaults] objectForKey:NumberKey] unsignedLongLongValue]];
You could look at using the NSNumber compare: function to see if the returned value is NSOrderedSame however this will not work for comparing unsigned vs signed values of the same type so in your situation I'd use the above as retrieving the data from NSUserDefaults is stripping the "signedness" of your number.
At the end of the day if you want to store NSNumber into NSUserDefaults this code works for me even for large integers like: 881217446193276338
To save:
[[NSUserDefaults standardUserDefaults] setObject:self.myUser.sessionid forKey:#"sessionid"];
[[NSUserDefaults standardUserDefaults] synchronize];
To recover:
self.myUser.sessionid = (NSNumber *)[[NSUserDefaults standardUserDefaults] objectForKey:#"sessionid"];
It's storing it correctly, nothing is wrong with your code except:
NSLog(#"Current Number:%#", number);
Here number is a non-string object, you might think of it as a wrapper for a numerical primitive. Or you might think that NSNumber instances objectify a primitive type.
What you need is some thing like:
NSLog(#"Current Number:%#", [number stringValue]);
Here is a speculative answer:
The NSNumber documentation states that:
(Note that number objects do not necessarily preserve the type they are created with.) .
So it must be using a different internal storage for this type, and only gives you the correct value when you specifically ask for the unsigned long long value. The description method, which is called in your NSLog statement, may be defaulting to a different representation type.
And / or there may be some quirk of the unarchiver that is preventing the isEqualToNumber method working on the value returned from defaults. If you do that comparison between two NSNumbers created in the same scope, does it work? The correct value is definitely in there somewhere given your last statement returns true.
Is it possible in an NSArray to find out if a given value exists or not in the array (without searching it using a for loop)? Any default random method. I went through the documentation, but didn't find much relevant.
Please also tell me about valueForKey method (I was unable to get that from doc).
The containsObject: method will usually give you what you're asking - while its name sounds like you are querying for a specific instance (i.e. two object with the same semantic value would not match) it actually invokes isEqual: on the objects so it is testing by value.
If you want the index of the item, as your title suggests, use indexOfObject:, it also invokes isEqual: to locate the match.
valueForKey: is for when you have an array of dictionaries; it looks up the key in each dictionary and returns and array of the results.
I believe you want to use the indexOfObject method. From the documentation:
indexOfObject:
Returns the lowest index whose
corresponding array value is equal to
a given object.
- (NSUInteger)indexOfObject:(id)anObject
Parameters
anObject
An object.
Return Value
The lowest index whose corresponding
array value is equal to anObject. If
none of the objects in the array is
equal to anObject, returns NSNotFound.
Discussion
Objects are considered equal if
isEqual: returns YES.
Important: If anObject is nil an
exception is raised.
You can use :
NSInteger idx = [myArray indexOfObject:obj];
to find index of object.
And to check if object is there or not in array you may use :
- (BOOL)containsObject:(id)anObject
Use NSPredicate to filter an NSArray based on NSDictionary
array = [dictionary filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:#"(key == %#)", value]];
if([array count]>0)
{
value exists;
}
Combine objectAtIndex and indexOfObject like this:
[tmpArray objectAtIndex:[tmpArray indexOfObject:yourObject]];
I am having a problem with a for loop. Most probably it is a silly mistake somewhere that i cant catch. I have a fast enumeration loop that looks like this:
for (NSNumber *number in sums) {
int n = [number intValue];
NSArray *array = [self getResultForTarget:n];
for (NSNumber *num in array) {
NSLog(#"%i",[num intValue]);
}
}
the value for [num intValue] is the same for every enumeration of for (NSNumber *number in sums) when it is impossible for it to be the same. It is giving the value it calculates in the first enumeration. The method getResultForTarget: cannot return the same result for the different (int) arguments it is taking.... what might be going wrong???
p.s. i tried to manually enter the arguments of sums in the method and it returned correct results.
If you manually entered sums and got the right results there is a good chance that the issue is that at run time sums does not contain what you think it contains.
ok i got it to work... apparently i have an initialized array that should be emptied before each call ...
if i try to access a nsmutableArray with objectAtIndex:x and if i have no object at this index, my app always crash.
So my question is: how can i check, if there is something at this index, without crashing the app?
I hope your understand my question.
Thanks, Alex
Check if your index is in array's bounds range:
if (index >=0 && index < [myArray count])
...
NSArray has a method called "count".
Call count on your mutable array and it will tell you the number of elements in the array.
You have two options: Use the count method to ensure you're within the bounds of the array, or catch the exception when you try to use objectAtIndex: Checking the range with count will be much lower overhead than catching the exception.
In case you didn't know - there are no "holes" allowed in an NSArray - the objects from index 0 to the end of the array ([array count]-1) will all be accessible.
If you are within the array's bounds, you will always have an object at a specific index between 0 and [array count], as the array cannot have gaps of nil values in it.
Try this
for(i=0; i< [myMutableArrayObject count]; i++) {
NSLog(#"%#",[[myMutableArrayObject objectAtIndex: i] myMethodDefined]);
}
Here, we are using a method predefined called count which returns the number of objects in the MutableArray Object
and then another method objectAtIndex which iterates the objects at the interval from 0 to (count – 1).
Regards,
Sumit