CODEWITHSUNDEEP
objective-c
ben3019201
ben3019201

Reputation: 391

Objective-C Implementing a class (Initialization of array)

My initialization of my array is getting a weird error. Anything I'm missing? The error is at the gameBoard array.

@implementation TicTacToe

- (id)init
{
    self = [super init];
    if (self)
    {
        gameBoard [3][3] = {{0, 0, 0},
                            {0, 0, 0},
                            {0, 0, 0}}; // error is saying: "expected expression"
        turn = 1;
        winner = 0;
        cellsChosen = 0;   
    }
    ...

Upvotes: 0

Views: 475

Answers (2)

iHunter
iHunter

Reputation: 6205

You have your gameBoard declared in @interface TicTacToe, right? Then you cannot use C array initialization syntax, because your array is already initialized. Unfortunately C doesn't provide a shortcut to assign arrays, so you should create a temporary array initialized with your values and then use memcpy to copy its elements to your array.

...
if (self)
{
    int tmpGameBoard[3][3] = {{0, 0, 0},
                              {0, 0, 0},
                              {0, 0, 0}};
    NSAssert(sizeof(tmpGameBoard) == sizeof(gameBoard),
             @"gameBoard is not a 3x3 array");
    memcpy(gameBoard, tmpGameBoard, sizeof(tmpGameBoard));
...

NSAssert is used to make sure you haven't changed your array size in interface and forgot to update its initialization (It would be better to use compile time assertion instead of NSAssert, but that's another topic).

Upvotes: 1

justin
justin

Reputation: 104698

an objc initializer is not a 'proper' initializer. your memory for your ivars already exists and it has been initialized with zeroed memory. so you are not using actual initialization syntax in this scope. this is why a const ivar is not useful, unless you are happy with using zeroed memory exclusively for that ivar (or you're into breaking const promises).

you can use assignment for the type (creating a temporary), or you can use the usual memory copying.

Upvotes: 0

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