Objective C - How to receive two int in same parameter

Question

I need to write a method like this:

-(void)doStuff:(int)options;

Based in the a typedef enum like this:

typedef enum
{
    FirstOption,
    SecondOption,
    ThirdOption
} MyOptions

What I need to to do in order to be able to call the method in this way (i.e. calling the method with more than one option "enabled":

[self doStuff:(FirstOption | ThirdOption)];

Do I need to setup the typedef enum differently? And how I check the options received in the method, a simple if (options == ...)?

fabrice truillot de chambrier · Accepted Answer · 2012-07-26T15:23:46.463

4

What you call for is a bit array. Define your options like this:

enum MyOptions
{
    FirstOption = 0x01, // first bit
    SecondOption = 0x02, // second bit
    ThirdOption = 0x04, // third bit
    ... = 0x08 ...
};

Combine the options like you suggested, with |, and test for them with & (options & SecondOption).

- (void) doStuff: (MyOptions) options
{
    if ( options & FirstOption )
    {
        // do something fancy
    }

    if ( options & SecondOption )
    {
        // do something awesome
    }

    if ( (options & SecondOption) && ( options & ThirdOption) )
    {
        // do something sublime
    }
}

edited Jul 26 '12 at 15:23

answered Jul 26 '12 at 14:36

fabrice truillot de chambrier

5,548
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1

For clarity I would add something explicit about the numbers being powers of two. – Almo Jul 26 '12 at 14:37
2

You could also use the built-in binary notation available if it makes it easier to read for you: `0b0001`, `0b0010`, `0b0100`, `0b1000`. – Richard J. Ross III Jul 26 '12 at 14:42
3

The conventions in apples code is to do a bitshift operation when setting up these masks: `FirstOption = 1, SecondOption = 1 << 1;` – wattson12 Jul 26 '12 at 14:44
@fabricetruillotdechambrier I am not being able to test for them with `&`. If you could please explain more, or explain about Apple conventions would be perfect. – Natan R. Jul 26 '12 at 14:57
It's not Apple-ish things, it's basic C. But hop, added an example. – fabrice truillot de chambrier Jul 26 '12 at 15:24
@fabricetruillotdechambrier Merci ;) – Natan R. Jul 26 '12 at 16:13
A votre service, Monsieur. :) – fabrice truillot de chambrier Jul 26 '12 at 16:21

score 1 · Answer 2 · edited May 23 '17 at 11:55

1

I'm no expert at Obj-C, but in other languages I would use flags. If each value is a power of two, then it will have only one bit set for that value. You can use that bit as a bool for a particular option.

FirstOption = 1
SecondOption = 2
ThirdOption = 4

FirstAndThird = FirstOption | ThirdOption; // Binary Or sets the bits

// Binary And checks the bits
IsFirst = FirstAndThird & FirstOption == FirstOption; // is true
IsSecond = FirstAndThird & SecondOption == SecondOption; // is false
IsThird = FirstAndThird & ThirdOption == ThirdOption; // is true

This question may also be of use.

edited May 23 '17 at 11:55

Community

1
1

answered Jul 26 '12 at 14:37

Corey Ogburn

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Compile errors/warnings with `IsFirst = FirstAndThird & FirstOption == FirstOption` – Natan R. Jul 26 '12 at 15:02
It's a language agnostic example. – Corey Ogburn Jul 26 '12 at 17:11

Objective C - How to receive two int in same parameter

2 Answers2