Question

I’m binding a ObjC library and it all works well, but I have one problem.
The ObjC library is using some values that are defined in a separate header.

For example, a header with:

#define SOME_PROPERTY_1 TRUE
#define SOME_PROPERTY_2 TRUE
#define SOME_PROPERTY_3 FALSE

Dependant on these properties, the library will make some changes to the view (so these changes are in the library, not in my C# code).

I would like to have access to these properties from my C# code so that I can change them. Now I need to build my library again if I want to change them and I can’t change them dynamically (what the goal is).

Is this possible?

I have searched on this, but I didn’t understand the two proposed solutions:

1. Putting them in my C# code instead of in my binding
   -> I assume this is not a solution, because in that case the library will not know about these changes? (no connection)
2. Binding them as (static) properties

Unfortunately, I don’t know how to do this. In this header, these is no Class/Interface, only #DEF statements, so I don’t know in which ‘class’ I should define these properties.

The header is then included in some other ObjC classes. I was trying to see if I could define them there, but it’s an interface and properties are not accepted.

So basically, there is a “SomeController” class that I’m binding and the “SomeController.h” is defined as interface

@interface SomeController : UIViewController

And in the “SomeController.m” you then have

#import "Constants.h" //The file with only #DEF statements
@implementation SomeController
{
...
}

Any ideas?

Regards,
Matt

Answer 1

This is not possible, because your SOME_PROPERTY_# aren’t actually variables, they’re preprocessing directives.

This means that the ObjectiveC preprocessor will replace all instances of SOME_PROPERTY_# in your source code with the value you defined it to be, but there is no SOME_PROPERTY_# variable/constant in the final executable.

For example:

#define SOME_PROPERTY_1 TRUE
void foo ()
{
    Bool value = SOME_PROPERTY_1;
}

will be converted to this by the preprocessor:

void foo ()
{
    Bool value = TRUE;
}

As you can see there is no SOME_PROPERTY_1 in the converted source code.

This means that you can’t change the value of SOME_PROPERTY_# dynamically.