I need to create a custom array:
In php I would define as follows:
$myarray[100][80] = 1;
But I don't know how to do it in objective-c...
I don't need an array [0][0],[0][1],[0][2], ... I only need concrete positions in this array [80][12], [147][444], [46][9823746],...
The content of these positions always will be = 1;
for this you would use a dictionary rather than an array as they are always 0,1,2 keyed so something along the lines of:
NSNumber *one = [NSNumber numberWithInt:1];
NSString *key = #"80,12";
NSDictionary *items = [NSDictionary dictionaryWithObject:one forKey:key];
Then to pull them out again you would use the objectForKey: method.
You cannot put ints directly into arrays or dictionaries that's why it is wrapped in the NSNumber object. To access the int after getting the NSNumber out of the dictionary you would use something like:
NSNumber tempNum = [items objectForKey:key];
int i = tempNum.intValue;
See the docs here for a full explanation of the NSDictionary class. Hope this helps...
I an not a PHP master but I believe in php arrays are not real arrays they are hash tables right?
Anyway, I think you are looking for NSDictionary or NSMutableDictionary class.
That looks more like a bitset than an array.
Allocating so many cells for that seems useless, so maybe you could revert the problem, and store the positions in an array.
Well in objective c we can use NSMutableArray to define 2-D arrays.
See the following code, it might help you
NSMutableArray *row = [[NSMutableArray alloc] initWithObjects:#"1", #"2", nil];
NSMutableArray *col = [[NSMutableArray alloc] init];
[col addObject:row];
NSString *obj = [[col objectAtIndex:0] objectAtIndex:0];
NSLog(#"%#", obj);
Related
How can I add object at specified index?
in my problem
NSMutableArray *substring
contains index and object alternatively
and I need to add it to the another array str according to index I getting from this array.
NSMutableArray *str=[NSMutableArray new];
if ([substrings containsObject:#"Category-Sequence:"])
{
NSString *index=[substrings objectAtIndex:5];
//[substrings objectAtIndex:5]
gives me integer position at which I need to add object in `str` array,
gives 5,4,8,2,7,1 etc
NSString *object=[substrings objectAtIndex:1];
//[substrings objectAtIndex:1] gives object,gives NSString type of object
[str insertObject:object atIndex:(index.intValue)];
}
please suggest some way to achieve it.
Thanks in advance!
Allocate the array first & then try to add objects in it.
NSMutableArray *str = [[NSMutableArray alloc]init];
if ([substrings containsObject:#"Category-Sequence:"])
{
NSString *index=[substrings objectAtIndex:5];
NSString *object=[substrings objectAtIndex:1];
[str insertObject:object atIndex:(index.intValue)];
}
Allocate the NSMutableArray before inserting objects into it:
NSMutableArray *strMutableArray = [[NSMutableArray alloc] init];
(You’ll also need to release it when you’re done if you’re not using ARC.)
Or you could also use a temporary object, if you don’t need to keep strMutableArray:
NSMutableArray *strMutableArray = [NSMutableArray array];
Then you can insert objects into the NSMutableArray.
Be careful with using indexes of and in different arrays, however. There might be a better way to do what you want.
I am having a problem that I think I am overcomplicating.
I need to make either an NSMutableArray or NSMutableDictionary. I am going to be adding at least two objects like below:
NSMutableArray *results = [[NSMutableArray alloc] init];
[results addObject: [[NSMutableArray alloc] initWithObjects: [NSNumber numberWithInteger:myValue01], #"valueLabel01", nil]];
This gives me the array I need but after all the objects are added I need to be able to sort the array by the first column (the integers - myValues). I know how to sort when there is a key, but I am not sure how to add a key or if there is another way to sort the array.
I may be adding more objects to the array later on.
Quick reference to another great answer for this question:
How to sort NSMutableArray using sortedArrayUsingDescriptors?
NSSortDescriptors can be your best friend in these situations :)
What you have done here is create a list with two elements: [NSNumber numberWithInteger:myValue01] and #"valueLabel01". It seems to me that you wanted to keep records, each with a number and a string? You should first make a class that will contain the number and the string, and then think about sorting.
Doesn't the sortedArrayUsingComparator: method work for you? Something like:
- (NSArray *)sortedArray {
return [results sortedArrayUsingComparator:(NSComparator)^(id obj1, id obj2)
{
NSNumber *number1 = [obj1 objectAtIndex:0];
NSNumber *number2 = [obj2 objectAtIndex:0];
return [number1 compare:number2]; }];
}
I am using insertObject for NSMutableArray for storing values into two dimensional array like below for example.
[mutableArrayPtr insertObject:[NSMutableArray arrayWithObjects:firstData, secondData,nil] atIndex:index];
I think, it is correct way of storing values in two dimensional array in Obj C.
I want to access it at later point of time. How can i do that?
Thanks!
The way you are doing it is perfectly fine. NSArray's don't have native two dimensional syntax like primitive arrays (int[][], double[][], etc.) in C do. So instead, you must nest them using an array of arrays. Here's an example of how to do that:
NSString *hello = #"Hello World";
NSMutableArray *insideArray = [[NSMutableArray alloc] initWithObjects:hello,nil];
NSMutableArray *outsideArray = [[NSMutableArray alloc] init];
[outsideArray addObject:insideArray];
// Then access it by:
NSString *retrieveString = [[outsideArray objectAtIndex:0] objectAtIndex:0];
To access your array at a later point in time, you would do something like:
NSArray* innerArray = [mutableArrayPtr objectAtIndex:0];
NSObject* someObject = [innerArray objectAtIndex:0];
Of course, change 0 to whatever index you actually need to retrieve.
EDIT:
Q: Is it "initWithObjects" (or) "insertObject:[NSMutableArray arrayWithObjects:imagePtrData,urlInStr,nil]" for two dimension?
A: initWithObjects and insertObject would both allow you to create two dimensional arrays. For example you could do:
NSMutableArray* arrayOne = [[NSMutableArray alloc] initWithObjects:[NSArray initWithObjects:#"One", #"Two", #"Three", nil], [NSArray initWithObjects:[#"Four", #"Five", #"Six", nil], nil];
// NOTE: You need to release the above array somewhere in your code to prevent a memory leak.
or:
NSMutableArray* arrayTwo = [NSMutableArray array];
[arrayTwo insertObject:[NSArray arrayWithObjects:#"One", #"Two", #"Three", nil] atIndex:0];
In my iPhone app, I am using an array which contains the values like shown below:
A:{
1000,
2000,
-1000,
4000
}
Now I want to convert this to the array shown below.
NSArray *A = [[NSArray alloc] initWithObjects:[NSNumber numberWithInt:1000],[NSNumber numberWithInt:2000],[NSNumber numberWithInt:-1000],[NSNumber numberWithInt:4000],nil];
How can I do that?
Edit:
Also I cannot use the value of Array A:{1000,2000,-1000,4000} to directly pass it into the NSNumber numberWithInt method, because it takes these values as NSString and not integers.
regarding to another question I saw from you I'm guessing those values are NSStrings
then use something like this.
NSMutableArray *array = [NSMutableArray array];
for (NSString *numberString in numberStringArray) {
[array addObject:[NSNumber numberWithInteger:[numberString integerValue]]];
}
and to be honest I think you should invest more time for the basics before you try to make use of core-plot
Is it acceptable to have a NSMutableArray within an NSDictionary? Or does the NSDictionary also have to be mutable?
The NSMutableArray will have values added to it at runtime, the NSDictionary will always have the same 2 NSMutableArrays.
Thanks,
Dan
Yes, it's perfectly acceptable. Keep in mind, the contents of the array are the pointers to your NSMutableArrays--those are what can't change in the immutable dictionary structure. What the pointers point to can change all you want. To wit:
NSMutableArray *arr = [[NSMutableArray alloc] init];
NSDictionary *dict = [NSDictionary dictionaryWithObject:arr forKey:#"test"];
[arr addObject:#"Hello"];
NSString *str = [[dict objectForKey:#"test"] objectAtIndex:0];
NSLog("%#", str);
It's quite acceptable. But, it's precisely the sort of setup that suggests you should seriously consider replacing the dictionary with an NSObject subclass that sports two properties for accessing the arrays.