CODEWITHSUNDEEP
objective-cnsmutablearray
MrHappyAsthma
MrHappyAsthma

Reputation: 6522

NSMutableArray Count

I am reading through some code and I came across the following statement and it seems to make absolutely no sense. The line is coded below. It takes the first object of an NSMutableArray and then sends the "count" message. What exactly is this doing?

for (int j = 0; j < [[inputData objectAtIndex:0] count]; j++)
//inputData is just an NSMutableArray

Could someone please explain this to me? I have never come across this before. I thought at first maybe it was like a 2-D array scenario where array[x].length is different from array.length, but inputData is just a single NSMutableArray of like 10 numbers.

Upvotes: 1

Views: 2667

Answers (2)

ilhnctn
ilhnctn

Reputation: 2210

If your array(in this case inpuData) has a key-value matching mechanism, this loop will increment its index but since everytime the condition is the same(the count of [inputData objectAtIndex:0] will never change ) this will cause an infinite loop

Upvotes: 2

JeremyP
JeremyP

Reputation: 86651

If you are correct that inputData contains NSNumbers, then what happens is that the first time through, you get an exception because NSNumber does not respond to -count.

The only way that code would do anything else is if [inputData objectAtIndex:0] responds to -count. It can be any object that responds to -count not just an array. Actually, it would also not throw an exception if inputData was nil. The expression would then return 0 (sending objectAtIndex: to nil returns nil and sending count to nil returns 0).

Upvotes: 0

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