Get Index of specific instance of object while iterating through NSArray. (Duplicates are messing this up)

Question

I've finally pinpointed the exact issue to a problem I've been having, but I'm not sure how to fix it. Here is the general gist of what is happening: I have an array called wordArray, and I am iterating through it. This array can contain strings that are identical to each other and different from one another. All I want to do is retrieve the index of the particular instance that I am currently iterating, so I the simplified version is this:

for(NSString* stringInWordArray in wordArray){
            NSLog(@"String is: %@ Index is: %d",stringInWordArray,[wordArray indexOfObject:stringInWordArray]);
}

This will obviously print out the String, and the index of the string, however, according to the apple documentation, the indexOfObject method "Returns the lowest index whose corresponding array value is equal to a given object." This is a problem for me because if I have an array that looks like this:

["fruit","fruit","panda","happy",nil];

Then this will print:

String is fruit Index is 0
String is fruit Index is 0
String is panda Index is 2
String is happy Index is 3

Where I want the indices to print 0,1,2,3. Any workarounds for this issue?

rmaddy · Accepted Answer · 2014-07-20 21:38:05Z

3

Use a "normal" loop:

for (NSUInteger i = 0; i < wordArray.count; i++) {
    NSString *stringInWordArray = wordArray[i];
    NSLog(@"String is: %@ Index is: %u",stringInWordArray, i);
}

Or you can do:

NSUInteger i = 0;
for(NSString* stringInWordArray in wordArray) {
    NSLog(@"String is: %@ Index is: %u",stringInWordArray, i);
    i++;
}

Or you can do:

[wordArray enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
    NSString *stringInWordArray = obj;
    NSLog(@"String is: %@ Index is: %u",stringInWordArray, idx);
}];

answered Jul 20, 2014 at 21:38

rmaddy

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3 Comments

arc4randall Over a year ago

wow this seems so obvious now that you say it lol... So caught up with the rest of the problem I couldnt think straight. Thanks!

Ken Thomases Over a year ago

With the middle option, be careful if you add logic that may use the continue statement. It will skip the increment. Oh, also, with modern compilers you can just use the desired type for the block parameter directly, without a local. I.e. ... enumerateObjectsUsingBlock:^(NSString* stringInWordArray, NSUInteger idx, ...

rmaddy Over a year ago

Would someone care to explain why this was down voted? How is this answer unhelpful or incorrect? No one learns otherwise.

DeveloBär · Accepted Answer · 2014-07-20 21:41:42Z

0

You could use a NSDictionary with key = index and the value = your string:

NSDictionary *dict = @{@"0" : @"fruit", @"1" : @"friut", @"2" : @"panda", @"3" : @"happy"};

The keys are unique, so you know which object you use depending on the key.

answered Jul 20, 2014 at 21:41

DeveloBär

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