Swift-Swift中的C API枚举 [英] Swift - C API enum in Swift

问题描述

我有如下定义的C API：

I have C API defined like this:

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

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

如何在Swift中使用 Foo 枚举直？我知道，我可以执行 var数据：Foo = A ，但是我不喜欢这种语法，其中 A 似乎成为一些全局变量。

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.

我宁愿拥有 var数据：Foo = Foo.A 或类似标准枚举的东西。有办法吗？

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

推荐答案

C枚举作为枚举如果它们是通过 NS_ENUM 或 CF_ENUM 宏定义的，请参见如何快速导入c枚举。

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 是在Core Foundation框架的 CFAvailability.h 中定义的，因此您必须导入如果文件尚未通过其他Core Foundation间接导入，则包含文件：

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
};

如果您查找 CF_ENUM 的定义，您会看到它是根据Clang定义的 enum_extensibility 属性，并扩展为

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;

两个声明都导入到Swift中，

Both declarations are imported to Swift as

public enum Foo : Int32 {
    case A
    case B
}

，后者不需要其他包含文件。

and the latter version does not need additional include files.

（用于打开和关闭之间的区别枚举，请参见 SE 0192处理未来枚举案例。）

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

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