快速 NSMutableArray 问题

Question

I was wondering, would using a NSMutableArray be the best way for making an array that i will be adding objects to? Or, just a regular NSArray? secondly, I'm trying to make something sort of like an ArrayList in java (so there is no limit to the size), and I would like to know how to do that. What I've thought of is to make a bigger array and copy older array into it. My code:

- (void) addAccount:(BankAccount *)b
{

accountCount = [NSNumber numberWithDouble:[accountCount doubleValue] + 1];    
NSMutableArray *oldList = accounts;
accounts = [[NSMutableArray alloc] (some code to make bigger and copy over)];

}

PS I taught myself this language yesterday, so I may not understand you response if it's too advanced

Answer 1

The difference between an NSMutableArray and an NSArray lies in the meaning of the word "mutable". ie: A mutable array can be modified after it's created whereas a "normal" NSArray is immutable and can't be modified after it's created.

As such, using an NSMutableArray and adding objects to it via the addObject: method would seem an ideal solution.

Answer 2

NSMutableArrays are what you want. Also, NSMutableArrays are already like ArrayLists or STL vectors, or anything else with "no limit to the size". You can say [myArray addObject:someObject]; until you run out of memory, and it will just keep resizing itself as needed.

Answer 3

1. If you want to be adding objects all at once use NSArray . If you're going to be adding some objects now, then more later, use NSMutableArray .

2. Your code snippet doesn't make much sense. To make an NSMutableArray , do this:

   NSMutableArray *array = [NSMutableArray array];

Answer 4

If you don't need an order (normally you don't), use a NSSet/NSMutableSet.