Math logic to substitute if statement

Question

The below code works, but I'm trying to come up with some math logic and use some binary operator to put in place of this if statement.

NSInteger indexCor = 0;
    for (PFObject *object in self.objects) {
        if (object == custom) {
            if (indexCor < 2) {
                NSLog(@"rodou indexCor <=2.");
                [self.coresConjugadosDict setObject:self.uiColorsArray[0] forKey:object.objectId];
                indexCor++;
            }
            else if (indexCor < 4) {
                [self.coresConjugadosDict setObject:self.uiColorsArray[1] forKey:object.objectId];
                indexCor++;
            }
            else if (indexCor < 6) {
                [self.coresConjugadosDict setObject:self.uiColorsArray[2] forKey:object.objectId];
                indexCor++;
            }
            else if (indexCor < 8) {
                [self.coresConjugadosDict setObject:self.uiColorsArray[3] forKey:object.objectId];
                indexCor++;
            }
            else if (indexCor < 10) {
                [self.coresConjugadosDict setObject:self.uiColorsArray[4] forKey:object.objectId];
                indexCor++;
            }
            else if (indexCor < 12) {
                [self.coresConjugadosDict setObject:self.uiColorsArray[5] forKey:object.objectId];
                indexCor++;
            }
            else {
                [self.coresConjugadosDict setObject:self.uiColorsArray[6] forKey:object.objectId];
                indexCor++;
            }
        }

So basically, some objects are going to be combined with another object. What I need to do is to set one UIColor for each group of two combined objects. I have a NSArray with the UIColors I want to use, and right now, what happens is that each object that meets the specific criteria I add the first color in the array, increment it. This way, each group of two objects will be of a different color.

So, if have 6 objects...

Objects 1,2 = Color 1 Objects 3,4 = Color 2 Objects 5,6 = Color 3

and so on.

I would like to achieve this without the if statement.

Sergey Kalinichenko · Accepted Answer · 2014-07-30T17:06:50.847

4

It looks like you'd like to make these transformation:

indexCor    uiColorsArray index
--------    -------------------
0, 1        0
2, 3        1
4, 5        2
6, 7        3
8, 9        4
10, 11      5
12 and up   6

This can be achieved by integer-dividing indexCor by 2, and limiting the result to 6, like this:

[self.coresConjugadosDict
    setObject:self.uiColorsArray[min(indexCor++/2, 6)]
    forKey:object.objectId];

Note: you may need to define your own min function to use the above code; the code above will not work correctly with a simple MIN macro, unless you move indexCor++ on a separate line.

Demo of the concept on ideone.

edited Jul 30 '14 at 17:06

answered Jul 30 '14 at 16:36

Sergey Kalinichenko

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Note - you can use the standard `MIN` macro if you move the increment of `indexCor` to its own line. – rmaddy Jul 30 '14 at 17:04
Thanks, this is what I was looking for. Although, how can I define my own min function? I'm trying to redefine min macro, but as you stated, it is not working. – Jorge Jul 30 '14 at 17:25
@Jorge Take a look at the demo, I defined a `min` function there. – Sergey Kalinichenko Jul 30 '14 at 17:27
I'm getting the error: Undefined symbols for architecture armv7: "_min", referenced from: _main in main.o – Jorge Jul 30 '14 at 17:39
when trying to test the function on main.m, just like your demo. – Jorge Jul 30 '14 at 17:40
1

@Jorge This is because I defined `min` with the `inline` marker. Here is [an answer that explains how to do it correctly](http://stackoverflow.com/a/5229551/335858) - you need a definition in a header, and an `extern inline ...` definition in a .m file. If you do not have to use `min` in other files, you could also define it in your .m file above the `@implementation`. – Sergey Kalinichenko Jul 30 '14 at 17:43
Perfect! Thanks for the patience. Now, if I wanted to start over the colors `array` after a certain number on `indexCor`, or return the value of `indexCor` to 0 after a limit, could I do that? – Jorge Jul 30 '14 at 18:02
1

@Jorge Absolutely, you can do that: simply add an `if` that checks `indexCor`, and resets it once it passes the upper limit. – Sergey Kalinichenko Jul 30 '14 at 18:09

Math logic to substitute if statement

1 Answers1