My question is as it is in the title. However, if it isn't an object, how can it then be maintained in NSMutableArray as an object? Because NSMutableArray is only for storing objects or am I wrong? :)
Primitive types, like int, must be wrapped in an object before it can be added to a collection class like NSMutableArray. Try this:
int nameOfVariable = 42;
NSMutableArray *array = ... // the initialized array
[array addObject:#(nameOfVariable)];
The last line is modern syntax that essentially means:
[array addObject:[NSNumber numberWithInt:nameOfVariable]];
Later on, when you need to get the value back, you do:
int someVariable = [array[someIndex] intValue];
No, it is not an object and you can therefore not put it in an NSArray. You have to wrap it in an NSNumber, which is an object and can be put in an NSArray.
An int is a primitive type inherited from C (examples of other primitive types are char, long, float, etc.). These are not Objective-C objects. To add a primitive type to an NSMutableArray or any other Objective-C collection, you must wrap them in an object. For number types like int, you would use NSNumber as follows:
int i = 1;
[array addObject:#(i)]; // #(i) is equivalent to [NSNumber numberWithInt:i]
Related
I am using objective c to create a struct holding a variable length array. I know you can create an array of length n like so:
double array[n];
And i also believe in c++ you can declare:
vector<double> array;
where you do not have to declare the array length. Is there any way to do something similar in objective c? I am using ARC.
Thanks in advance, Ben
You just need to create an NSMutableArray like-
NSMutableArray *myArray = [NSMutableArray array];
[myArray addObject:....];// Add as many object as you want.
You just need to take care of one thing while creating variable length array, don't add nil as object, as nil is just to signify the end of the variable-length argument list.
EDIT -
Might be following will help you -
In this way you can define objective c data types in struct-
typedef struct{
int numInputs;
__unsafe_unretained NSMutableArray *array;
} Pin;
Is it possible to cast a NSInteger to a NSNumber object?
I need to convert the tag of a UIImageView object to a NSNumber object because I need to pass it as an argument to a function.
You cannot cast it because NSInteger is not an object, just an alias for a built-in type. You can always create a new NSNumber object from NSInteger, like this:
NSNumber *myNum = #(myNsIntValue);
or in the prior version of the compiler, use
NSNumber *myNum = [NSNumber numberWithInteger:myNsIntValue];
since Apple LLVM Compiler 4.0, there is an easier way to create NSNumber object:
NSNumber *x = #1234;
NSNumber *y = #(anIntegerVariable);
This is the more correct answer and it will not produce unexpected error.
NSNumber *myNum = [NSNumber numberWithInteger:myNsIntValue];
Because the doc said:
"numberWithInteger:
Creates and returns an NSNumber object containing a given value, treating it as an NSInteger."
"numberWithInt:
Creates and returns an NSNumber object containing a given value, treating it as a signed int."
a.H:
-(NSArray *) returnarray:(int) aa
{
unsigned char arry[1000]={"aa","vv","cc","cc","dd"......};
NSArray *tmpary=arry;
return tmpary;
}
a.c:
#include "a.H"
main (){
// how do I call returnarray function to get that array in main class
}
I need that array in main and I need to retain that array function in separate class.
Can someone please provide a code example to do this?
These lines:
unsigned char arry[1000]={"aa", "vv", "cc", "cc", "dd", ...};
NSArray *tmpary=arry;
Should instead be:
unsigned char arry[1000]={"aa", "vv", "cc", "cc", "dd", ...};
NSMutableArray * tmpary = [[NSMutableArray alloc] initWithCapacity: 1000];
for (i = 0; i < 1000; i++)
{
[tmpary addObject: [NSString stringWithCString: arry[i] encoding:NSASCIIStringEncoding]];
}
This is because a C-style array (that is, int arr[10]; for example) are not the same as actual NSArray objects, which are declared as above.
In fact, one has no idea what an NSArray actually is, other than what the methods available to you are, as defined in the documentation. This is in contrast to the C-style array, which you are guaranteed is just a contiguous chunk of memory just for you, big enough to hold the number of elements you requested.
C-style arrays are not NSArray's so your assignment of arry (the definition of which has some typos, at least the unsighned part) is not valid. In addition, you call arry an array of char, but you assign it an array of null-terminated strings.
In general you need to loop and add all the elements of the C-style array to the NSArray.
I'm not sure why you must do it in main. If you want a global you can do it by declaring a global in another file. That said, you CANNOT assign a plain C data array to an objective C NSArray, which is different in nature entirely.
I have an NSArray arr. It has a bunch of NSNumber objects. I'm trying to calculate statistics analysis on the array using GNU's GSL. GSL takes parameters as C-style arrays.
Is there any mechanism that can, for example, run 'intValue' on all of the objects in a NSArray object, and convert the results that to a C-style array?
I don't really want to copy the contents of the NSArray to a C-style array, as it's a waste of space and cycles, so I'm looking for an alternative.
The mechanism you're describing — run intValue on all the objects in the NSArray and give a C-style array — seems to be exactly the same thing you describe as "a waste of space and cycles." It's also the only real way to do this if you need a C-style array of ints. Best approach I can think of:
int *c_array = malloc(sizeof(int) * [yourArray count]);
[yourArray enumerateObjectsWithOptions:NSEnumerationConcurrent
usingBlock:^(id number, NSUInteger index, BOOL *unused) {
c_array[index] = [number intValue];
}];
Try this:
id *numArray = calloc(sizeof(id), yourArray.count);
[yourArray getObjects: numArray range: NSMakeRange(0, yourArray.count)];
That gives you a C-array of NSNumbers. An alternative that gives you ints:
int *numArray = calloc(sizeof(int), yourArray.count);
for (int i = 0; i< yourArray.count; i++)
numArray[i] = [[yourArray objectAtIndex: i] intValue];
There is no way to tell yourArray to return a C-array of ints directly. NSArray has no concept of the contents it has, except that they are ids, and must be retained and released at the right times. It can at most return a C-array of ids, as in my first example.
You could probably write your own simple array class that contains ints (or floats or doubles, etc.) directly, in an internal C array, but there is no stock class for this.
How can I solve this problem?
code:
[NSNumber numberWithInteger:[buttonStatsInSection objectAtIndex:row]]
warning: passing argument 1 of 'numberWithInteger:' makes integer from pointer without a cast
Thanks.
numberWithInteger: needs you to give it an int to create the NSNumber. You are giving it an object, because objectAtIndex: returns an object.
Even if the object you have at that row is an NSNumber, or anything else, you still need to get an actual int data type out of it somehow.
For example, if the object you get back is an NSNumber, you could have something like this in the end:
NSNumber * myNSNum = [buttonStatsInSection objectAtIndex:row];
int myInt = [myNSNum intValue];
[NSNumber numberWithInteger:myInt];
Why are you creating a new NSNumber object? Do you really want a copy of it, or do you just want a reference to it? What do you plan to do with it? If you want a copy, you can just do:
NSNumber* copy = (NSNumber*)[[buttonStatsInSection objextAtIndex:row] copy];
Otherwise just do:
NSNumber* num = (NSNumber*)[buttonStatsInSection objextAtIndex:row];
Either way it isn't necessary to go through the process of extracting the int value and the converting it right back to an NSNumber