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 ...
Related
I am making a calculator that logs input in a label named "inputLabel' and then outputs the answer in a different label named "outputLabel" (similar to a graphing calculator). Once the user is finished entering the expression, the expression is stored in an NSString object and then parsed with the NSPredicate class and evaluated with the NSExpression class. What I have works, but I have noticed for particular operations the answers are not correct. For example, if the user types in "25/2" the calculator returns 12, which is obviously incorrect. However, if the user types in "25/2.0" or "25.0/2" the calculator returns 12.5 which is what I want. It seems that the NSExpression method 'expressionValueWithObject' is interpreting the operands as integers instead of floats. If this is the case, is there a way that I change the 'expressionValueWithObject'method to interpret the operands as floats?
Brain.m
-(float)performCalculation: (NSString *)operation
{
NSPredicate *parsed = [NSPredicate predicateWithFormat:[operation stringByAppendingString:#"=1.0"]];
NSExpression *inputExpressionParsed = [(NSComparisonPredicate *)parsed leftExpression];
NSNumber *result = [inputExpressionParsed expressionValueWithObject:inputExpressionParsed context:nil];
return [result floatValue];
}
ViewController.m
- (IBAction)equalsPressed:(id)sender
{
//self.inputLabel.text = [self.inputLabel.text stringByAppendingString:#".0"];
NSString *inputExpression = self.inputLabel.text;
self.inputLabel.text = [self.inputLabel.text stringByAppendingString:#"="];
float result = [self.brain performCalculation:inputExpression];
self.outputLabel.text = [NSString stringWithFormat:#"%g", result];
}
No, NSExpression cannot do that. You could try to append ".0" to all integer numbers
in the string before evaluating it, but the better solution is probably to use a "proper"
math expression parser, for example
https://github.com/davedelong/DDMathParser
You could iterate through the expression tree replacing the expression with the integer value (expressionType == NSConstantExpression). It depends a little bit of the features of your calculator, whether it is worth or not.
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.
I've got this:
if ([[currentPlayer rankicon] isEqualToString:#"0"]) {
self.casteImage.image = [casteImages objectAtIndex:0];
}
Which works. However, I have some 16 images to assign, and since the NSString and the index id are the same, I'd like to find a more efficient way to do this. I've also tried:
NSInteger i = [[currentPlayer rankicon] integerValue];
self.casteImage.image = [casteImages objectAtIndex:[i]];
But that doesn't work. Could be a bug elsewhere in my code(or some syntax error in the above), of course, but was wondering if I'm anywhere near the right track.
Remove [] around iin the second line.
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
I've got an NSDictionary that was initialized with a plist that, among other things, contained count followed by 32 and I want to get at the value for count.
How?
I know how to get it into an object via
[dictionaryObjectName objectForKey:#"count"]
But to me, the value I'm obtaining is not an object.
If I have to specify an object, what would be the best one to use (FYI the value will always be unsigned) and I need to get it into a true int.
Do I do something like
NSNumber *num = [dictionaryObjectName objectForKey:#"count"];
int theValue = [num intValue];
[num release];
Is the release on num a good thing to do since this for an iPhone with no garbage collector?
And nicer form is:
int theValue = [[dictionaryObjectName objectForKey:#"count"] intValue];
EDIT
Since I see that people still arrive to this page, let's clarify that these days you simply do
int theValue = [dictionaryObjectName[#"count"] intValue];
Yes, you pull it out as an NSNumber, then grab the int(eger)Value but there's no need to release it. You didn't retain, alloc, or copy the number, so you don't have to worry about releasing it.