I need to keep track of integer values in an array, and sometimes I need to modify a value in the array.
Right now I do this:
// Read an integer from the array
NSNumber* num = [NSNumber numberWithInteger:someInteger];
[numArray addObject:num];
To update a value:
// Update an integer in the array
NSNumber* num = [numArray lastObject]; // get old
NSInteger numInt = [numInt integerValue]; // convert
NSNumber* newNum = [NSNumber numberWithInteger:numInt + someAddition]; // create new
[numArray removeLastObject]; // remove old
[numArray addObject:newNum]; // set new
This is so bad. So many objects involved and all because NSNumber is immutable. Now I thought maybe I must step down into good old C and use CFMutableArrayRef? Can I store simple NSInteger values in there without all this overhead?
You could use replaceObjectAtIndex: withObject: command:
[numArray replaceObjectAtIndex:[array count]-1 withObject:newNum];
It's better than your method
Related
Ok. i don't see ways to done it. But maybe some one knows?
I don't need use NSString to put it in array, because it makes huge memory usage.
NSMutableArray *array = #[#(-16.f)].mutableCopy;
for (NSNumber *number in array) {
NSLog(#"%f", number.floatValue);
}
first you need to convert yourfloat value toNSNumber using #(floatValue) .
NSMutableArray *arr = [[NSMutableArray alloc]init]; // here you can add value using initWithObject method.
[arr addObject:#(-16)]; // here you can add your float value using #(float value).
NSLog(#" array = %#",arr);
When you retrive value from array .
float yourValue = [[arr objectAtIndex:(your index)] floatValue];
hope it help you .
I want to create instance variables dynamically at runtime, and I want to add these variables to a category. The number of the instance variables may change based on the configuration/properties file which I am using for defining them.
Any ideas??
Use Associative References - this is tricky, but that is the mechanism invented specifically for your use case.
Here is an example from the link above: first, you define a reference and add it to your object using objc_setAssociatedObject; then you can retrieve the value back by calling objc_getAssociatedObject.
static char overviewKey;
NSArray *array = [[NSArray alloc] initWithObjects:# "One", #"Two", #"Three", nil];
NSString *overview = [[NSString alloc] initWithFormat:#"%#", #"First three numbers"];
objc_setAssociatedObject (
array,
&overviewKey,
overview,
OBJC_ASSOCIATION_RETAIN
);
[overview release];
NSString *associatedObject = (NSString *) objc_getAssociatedObject (array, &overviewKey);
NSLog(#"associatedObject: %#", associatedObject);
objc_setAssociatedObject (
array,
&overviewKey,
nil,
OBJC_ASSOCIATION_ASSIGN
);
[array release];
I'd be inclined to just use a NSMutableDictionary (see NSMutableDictionary Class Reference). Thus, you would have an ivar:
NSMutableDictionary *dictionary;
You'd then initialize it:
dictionary = [NSMutableDictionary dictionary];
You can then save values to it dynamically in code, e.g.:
dictionary[#"name"] = #"Rob";
dictionary[#"age"] = #29;
// etc.
Or, if you are reading from a file and don't know what the names of the keys are going to be, you can do this programmatically, e.g.:
NSString *key = ... // your app will read the name of the field from the text file
id value = ... // your app will read the value of the field from the text file
dictionary[key] = value; // this saves that value for that key in the dictionary
And if you're using an older version of Xcode (before 4.5), the syntax is:
[dictionary setObject:value forKey:key];
Depends on exactly what you want to do, the question is vague but if you want to have several objects or several integers or so on, arrays are the way to go. Say you have a plist with a list of 100 numbers. You can do something sort of like this:
NSArray * array = [NSArray arrayWithContentsOfFile:filePath];
// filePath is the path to the plist file with all of the numbers stored in it as an array
That will give you an array of NSNumbers, you can then turn that into an array of just ints if you want like this;
int intArray [[array count]];
for (int i = 0; i < [array count]; i++) {
intArray[i] = [((NSNumber *)[array objectAtIndex:i]) intValue];
}
Whenever you want to get an integer from a certain position, lets say you want to look at the 5th integer, you would do this:
int myNewInt = intArray[4];
// intArray[0] is the first position so [4] would be the fifth
Just look into using a plist for pulling data, it will them be really easy to create arrays of custom objects or variables in your code by parsing the plist.
I'm new in Cocoa.
I have NSString - (e.g) MUSIC . I want to add some new NSString in Array,
And want to check something like this
if MUSIC already contained in Array, add Music_1 , after Music_2 and so on.
So I need to be able read that integer from NSString, and append it +1 .
Thanks
Use
NSString *newString = [myString stringByAppendingString:[NSString stringWithFormat:#"_%i", myInteger]];
if myString is "music", newString will be "music_1" or whatever myInteger is.
EDIT: I seem to have gotten the opposite meaning from the other answer provided. Can you maybe clarify what it is you are asking exactly?
Check it out:
NSMutableArray *array = [NSMutableArray arrayWithObjects:#"123", #"qqq", nil];
NSString *myString = #"MUSIC";
NSInteger counter = 0;
if ([array containsObject:myString]){
NSString *newString = [NSString stringWithFormat:#"%#_%d", myString, ++counter];
[array addObject:newString];
}
else
[array addObject:myString];
For checking duplicate element in Array you can use -containsObject: method.
[myArray containsObject:myobject];
If you have very big array keep an NSMutableSet alongside the array.Check the set for the existence of the item before adding to the array. If it's already in the set, don't add it. If not, add it to both.
If you want unique objects and don't care about insertion order, then don't use the array at all, just use the Set. NSMutableSet is a more efficient container.
For reading integer from NSString you can use intValue method.
[myString intValue];
For appending string with number you can use - (NSString *)stringByAppendingString:(NSString *)aString or - (NSString *)stringByAppendingFormat:(NSString *)format ... method.
Here's how you convert a string to an int
NSString *myStringContainingInt = #"5";
int myInt = [myStringContainingInt intValue];
myInt += 1;
// So on...
I'm trying to access an array using another array integer value as an index.
NSInteger index=[appDelegate.randomRiddles objectAtIndex:appDelegate.randomRiddlesCounter];
int i = index;
questionText.text = [[appDelegate.currentRiddlesContent objectAtIndex:i] objectForKey:#"question"];
//where appDelegate.randomRiddlesCounter is an NSInteger and appDelegate.randomRiddles is a NSMutableArray
However I'm getting incompatible pointer to int conversion warning. How can I fix this above code? The warning I get is coming from the first line.
Try:
NSNumber *index = [appDelegate.randomRiddles objectAtIndex: appDelegate.randomRiddlesCounter];
int i = [index intValue];
questionText.text = [[appDelegate.currentRiddlesContent objectAtIndex: i] objectForKey: #"question"];
NSInteger is an integral type, not an object.
Try this:
int i = [index intValue];
An NSArray like object can only store Objective-C object pointers (i.e. everything that you can assign to an id)
With objectAtIndex you get the object, with indexOfObject:(id)anObject you get the corresponding index.
These two instructions are both valid:
id bla = [appDelegate.randomRiddles objectAtIndex:appDelegate.randomRiddlesCounter];
NSInteger index = [appDelegate.randomRiddles indexOfObject:myObject];
The second assumes that myObject is at least of type id
So you try to convert a pointer to an int. Therefore the warning is issued.
The following code snippet:
NSLog(#"userInfo: The timer is %d", timerCounter);
NSDictionary *dict = [NSDictionary dictionaryWithObject:[NSNumber numberWithInteger:timerCounter] forKey:#"timerCounter"];
NSUInteger c = (NSUInteger)[dict objectForKey:#"timerCounter"];
NSLog(#"userInfo: Timer started on %d", c);
produces output along the lines of:
2009-10-22 00:36:55.927 TimerHacking[2457:20b] userInfo: The timer is 1
2009-10-22 00:36:55.928 TimerHacking[2457:20b] userInfo: Timer started on 5295968
(FWIW, timerCounter is a NSUInteger.)
I'm sure I'm missing something fairly obvious, just not sure what it is.
You should use intValue from the received object (an NSNumber), and not use a cast:
NSUInteger c = [[dict objectForKey:#"timerCounter"] intValue];
Dictionaries always store objects. NSInteger and NSUInteger are not objects. Your dictionary is storing an NSNumber (remember that [NSNumber numberWithInteger:timerCounter]?), which is an object. So as epatel said, you need to ask the NSNumber for its unsignedIntegerValue if you want an NSUInteger.
Or like this with literals:
NSUInteger c = ((NSNumber *)dict[#"timerCounter"]).unsignedIntegerValue;
You must cast as NSNumber first as object pulled from dictionary will be id_nullable and so won't respond to the value converting methods.