Equivalent to static fields in IOS - ios

Question

I'm more of an Android developer, but i'm beginning to see the light at the end of the tunnel on iOS development.
There is, however, one coding pattern I can't seem to find an equivalent for.
The use of static fields as flags.
Android :
public final static int ERROR_EMPTY = 1;
public final static int ERROR_NO_CONNECTION = 2;
public final static int ERROR_WRONG_USER = 4;
...
if (error == MyClass.ERROR_EMPTY) {//do things}
What would be the proper way to achieve this on iOS ?
Thanks.

Answer 1

Using Objective-C and C
i often use prefixes:
typedef enum MyClass_Error {
// never use MyClass_Error_Undefined
// or you may favor MyClass_Error_None for a valid error code
MyClass_Error_Undefined = 0,
MyClass_Error_Empty = 1,
MyClass_Error_NoConnection = 2,
MyClass_Error_WrongUser = 4
// ...
} MyClass_Error;
for these value collections. then you get benefits such as typesafety and switch value checking.
for non-type constants:
enum { MyClass_ConstantName = 4 };
and feel free to hide these in the *.m when private.
also note that C enums may have gaps in their defined values (unlike Java's).
Update: there's an even better way to declare an enum, as demonstrated in Abizern's answer -- if you're sticking with the most recent toolchains. the big reason to use this extension is for binary compatibility and encoding (although i favor fixed-width types for these purposes).
There are a few other variations, for the cases when you want to use existing types:
Private Constant
MyClass.m
static const NSRange MyClass_InputRange = {1,1};
Public Constant
MyClass.h
extern const NSRange MyClass_InputRange;
MyClass.m
const NSRange MyClass_InputRange = {1,1};
Using C++
You would likely favor introducing a new scope for these values -- either in a class or a namespace, rather than simulating the scope using prefixes.
Common Mistakes
Use of #define for constants (unless definition is mandatory when preprocessing)
Use of short identifiers, and identifiers which are not prefixed
Use of static values in headers
Not using const when possible
Declaring them in the header, when they could be in the *.m source.

Answer 2

Just to add to Justin's excellent answer - the Modern Objective-C definition for the enum would be:
typedef enum MyClass_Error : NSUInteger {
// never use MyClass_Error_Undefined
// or you may favor MyClass_Error_None for a valid error code
MyClass_Error_Undefined = 0,
MyClass_Error_Empty = 1,
MyClass_Error_NoConnection = 2
// ...
} MyClass_Error;