Quickly Build an Input-Driven Game - Beginning iOS6 Games Development - page 83

The task coinForCoord: takes a Coord and returns the type of coin at that location. Finding the
NSNumber object at the given index in the NSMutableArray coins does this. The index is determined
by calling indexForCoord: , shown in Listing 4-16.
Listing 4-16. CoinsGame.m (indexForCoord:)
-(int)indexForCoord:(Coord)coord{
return coord.row*colCount + coord.col;
}
The task indexForCoord: takes a Coord struct. This simple task multiplies the number of columns in
the game by the row value of coord and adds the col value.
CoinsGame.m that should be explored to help you understand what
is doing during different parts of its life cycle. Let's continue by looking at the task
, shown in Listing 4-17.
CoinsGame.m (swap:With:)
int indexA = [self indexForCoord:coordA];
int indexB = [self indexForCoord:coordB];
NSNumber* coinA = [coins objectAtIndex:indexA];
NSNumber* coinB = [coins objectAtIndex:indexB];
[coins replaceObjectAtIndex:indexA withObject:coinB];
[coins replaceObjectAtIndex:indexB withObject:coinA];
}
The task swap:With: takes two Coords , coordA and coordB . This task switches the type of coins at
these two coordinates by finding the index of each coordinate, the current value of that index in
coins, and switching them. We know that after coins are swapped, CoinsController will have to look
for any matches. This is done with the tasks findMatchingRows and findMatchingCols . Listing 4-18
shows findMatchingRows.
Listing 4-18. CoinsGame.m (findMatchingRows)
-(NSMutableArray*)findMatchingRows{
NSMutableArray* matchingRows = [NSMutableArray new];
for (int r=0;r<rowCount;r++){
NSNumber* coin0 = [self coinForCoord:CoordMake(r, 0)];
BOOL mismatch = false;
for (int c=1;c<colCount;c++){
NSNumber* coinN = [self coinForCoord:CoordMake(r,c)];
if (![coin0 isEqual:coinN]){