Objective-C 中的前向声明枚举 [英] Forward-declare enum in Objective-C
问题描述
我在 Objective-C 程序中遇到枚举可见性的问题.我有两个头文件,一个定义了 typedef enum
.另一个文件需要使用 typedef
的类型.
I'm having trouble with enum visibility in an Objective-C program. I have two header files, and one defines a typedef enum
. Another file needs to use the typedef
'd type.
在直接的 C 中,我会简单地 #include
另一个头文件,但在 Objective-C 中,建议不要在头文件之间使用 #import
,而是使用根据需要转发 @class
声明.但是,我不知道如何向前声明枚举类型.
In straight C, I would simply #include
the other header file, but in Objective-C, it's recommended not to use #import
between header files, instead using forward @class
declarations as needed. However, I can't figure out how to forward-declare an enumeration type.
我不需要实际的枚举值,除了在相应的.m
实现文件中,我可以安全地#import
离开.那么如何才能在标题中识别 typedef enum
呢?
I don't need the actual enumerated values, except in the corresponding .m
implementation file, where I can safely #import
away. So how can I get the typedef enum
to be recognized in the header?
推荐答案
在 Objective-c 中转发声明枚举 (NS_ENUM/NS_OPTION) 的最新方法(Swift 3;2017 年 5 月)是使用以下内容:
Most recent way (Swift 3; May 2017) to forward declare the enum (NS_ENUM/NS_OPTION) in objective-c is to use the following:
// Forward declaration for XYZCharacterType in other header say XYZCharacter.h
typedef NS_ENUM(NSUInteger, XYZCharacterType);
// Enum declaration header: "XYZEnumType.h"
#ifndef XYZCharacterType_h
#define XYZCharacterType_h
typedef NS_ENUM(NSUInteger, XYZEnumType) {
XYZCharacterTypeNotSet,
XYZCharacterTypeAgent,
XYZCharacterTypeKiller,
};
#endif /* XYZCharacterType_h */`
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