Question

I want to ask about the NSArray in objective C.

I want to create a dynamic array as I don’t know about the size of the array. And I also want to insert some of the data to the array. However, I don’t know how to decl, init and insert the element in to the array.

The following is the C++ version.
I want to create a empty array A and put all the array element in array B to A.

// empty array

string arrA[] = new string();

// put the arrB into arrA

for(int i=0; i < arrB.length(); i++)

      arrA[i] = arrB[i];

Thank you very much.

Answer 1

You should use the class named NSArray or NSMutableArray. These are similar to std::vector however they are somewhat different in their use due to the way Objective-C works.

// Immutable array (must be created with contents specified)
NSArray *strings = [NSArray arrayWithObjects:@"Hello", @", world!", nil];

// Mutable array (can be modified)
NSMutableArray *strings = [NSMutableArray array];
[strings addObject:@"Hello"];
[strings addObject:@", world!"];

The difference with Objective-C NSArray objects is that they can take any type of object as long as it is a subclass of NSObject.

NSArray *array = [NSArray arrayWithObjects:@"A string", [NSNumber numberWithInt:1337], [NSDictionary dictionary]];

To access values you must use the objectAtIndex: message.

NSString *aString = [array objectAtIndex:10];
NSLog(aString);