Swift - C API enum in Swift

问题

I have C API defined like this:

typedef enum Foo {
   A = 0,
   B = 1
} Foo;

typedef struct Bar {
  int a;
  Foo foo;
} Bar;

How can I use Foo enum in Swift directly? I know, that I can do var data: Foo = A, but I dont like this syntax, where A seems to be some global variable.

I would rather have var data: Foo = Foo.A or something similar like with standard enums. Is there a way?

回答1:

C enumerations are imported into Swift as an enum if they are defined via the NS_ENUM or CF_ENUM macro, see for example How to import c enum in swift.

CF_ENUM is defined in CFAvailability.h from the Core Foundation framework, so you have to import that file if it is not yet imported indirectly via other Core Foundation include files:

#include <CoreFoundation/CFAvailability.h>

typedef CF_ENUM(int, Foo) {
    A = 0,
    B = 1
};

If you lookup the definition of CF_ENUM then you'll see that it is defined in terms of the Clang enum_extensibility attribute, and expands to

typedef enum __attribute__((enum_extensibility(open))) : int {
    A = 0,
    B = 1
} Foo;

Both declarations are imported to Swift as

public enum Foo : Int32 {
    case A
    case B
}

and the latter version does not need additional include files.

(For the difference between “open” and “closed” enums, see SE 0192 Handling Future Enum Cases.)

来源：https://stackoverflow.com/questions/60559599/swift-c-api-enum-in-swift