Expression is not an integer constant expression in iOS objective c

Question

I want to use the following expression

-(void)SwitchCondn{
    int expression;
    int match1=0;
    int match2=1;

    switch (expression)

    {
        case match1:

            //statements

            break;

        case match2:

            //statements

            break;

        default:

           // statements

            break;

    }

But I got

enter image description here

When I research I found

In order to work in Objective-C, you should define your constant either like this:
#define TXT_NAME 1
Or even better, like this:
enum {TXT_NAME = 1};

I have been using this methods since long time . Now my variable value will change in run time so I need to define in others way and i didn't want to use if else so is there any way of declaration variable others way

I have had study following

Why can I not use my constant in the switch - case statement in Objective-C ? [error = Expression is not an integer constant expression]

Objective C switch statements and named integer constants

Objective C global constants with case/switch

integer constant does 'not reduce to an integer'

Possible duplicate of [Why can I not use my constant in the switch - case statement in Objective-C ? \[error = Expression is not an integer constant expression\]](http://stackoverflow.com/questions/6585276/why-can-i-not-use-my-constant-in-the-switch-case-statement-in-objective-c-e) — gypsicoder, Nov 29 '16 at 08:50

score 12 · Answer 1 · answered Jun 29 '15 at 15:43

12

The error expression is not an integer constant expression means just what it says: in a case, the value must be constant, as in, not a variable.

You could change the declarations above the switch to be constants:

const int match1=0;
const int match2=1;

Or you could use an enumeration. Or a #define. But you can't use non-constant variables there.

answered Jun 29 '15 at 15:43

Tom Harrington

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will i be able to change the value of match1 where ever i wants – Nischal Hada Jun 29 '15 at 15:45
Not if you want to use it in a `case`. – Tom Harrington Jun 29 '15 at 15:46
no, as the error message points out, it's required to be a **constant**. – vadian Jun 29 '15 at 15:47
I have the condition that i need to declare const int match1 as universal and i need to set the value of const int match1 after i get data from server – Nischal Hada Jun 29 '15 at 15:47
Then you need to use something other than a `switch`. Maybe an `if`/`else if` chain. – Tom Harrington Jun 29 '15 at 15:49
i have been using #define previously but i need to declare value only after i get data from server so i got the problem – Nischal Hada Jun 29 '15 at 15:49
Ya if/else is the option but i want to know first if switch is possible or not – Nischal Hada Jun 29 '15 at 15:51
Ya thanks buddy. I have upvote for your efforts. Now i will try to implement it. Hope that u do same for my questions too – Nischal Hada Jun 29 '15 at 16:18
Does that means using if/else is the only option left – Nischal Hada Jun 29 '15 at 16:24
2

Using `const` before `int` does _not_ make this warning go away. At least not on Xcode 7.3.1 with `GCC_WARN_PEDANTIC = YES`. The only way to make it go away is with define macro or enum. – Jeff Jun 20 '16 at 12:26

score 6 · Answer 2 · answered Jun 29 '15 at 15:41

6

If you want to have labeled cases, you need a ENUM type

typedef NS_ENUM(int, MyEnum) {
  match1 = 0,
  match2 = 1
};

- (void)switchCondn:(MyEnum)expression {

  switch (expression)
  {
    case match1:
      //statements
      break;

    case match2:
      //statements
      break;

    default:
      // statements
      break;
  }
}

answered Jun 29 '15 at 15:41

vadian

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will i be able to change the value of match1 where ever i wants – Nischal Hada Jun 29 '15 at 15:45
I have the condition that i need to declare const int match1 as universal and i need to set the value of const int match1 after i get data from server. Can it be acheive – Nischal Hada Jun 29 '15 at 15:50
1

no, not in a switch expression. You have to use if - else or something similar – vadian Jun 29 '15 at 15:52
Thanks for your effort. I have upvoot for your effort hope to get that in question too – Nischal Hada Jun 29 '15 at 16:18
Does that means using if/else is the only option left – Nischal Hada Jun 29 '15 at 16:25
It seems so. Or you _switch_ to Swift. The switch statement in Swift is much more powerful – vadian Jun 29 '15 at 16:31

Expression is not an integer constant expression in iOS objective c

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