C 枚举和 XML 之间的转换 [英] Converting between C enum and XML

问题描述

在 XML 中存储枚举并再次读取它的最简洁方法是什么?说我有:

What's the cleanest way to store an enum in XML and read it back out again? Say I've got:

enum ETObjectType {ETNormalObjectType, ETRareObjectType, ETEssentialObjectType};

...我想获取一个变量，enum ETObjectType objectType = ETNormalObjectType;，并将其转换为如下所示的 XML:<objectType>ETNormalObjectType</objectType>.

...and I want to take a variable, enum ETObjectType objectType = ETNormalObjectType;, and convert it to XML that looks like this: <objectType>ETNormalObjectType</objectType>.

目前我正在做的事情是这样的:

Currently what I'm doing is something like this:

NSString* const ETObjectTypeAsString[] = {@"ETNormalObjectType",@"ETRareObjectType",@"ETEssentialObjectType"};

[anXMLElement addChild:[NSXMLElement elementWithName:@"objectType" stringValue:ETObjectTypeAsString[objectType]]];

...但这并不完全理想；每次更改枚举时，我都不乐意更新这两个列表.但这是可以接受的.更糟糕的是重新读取 XML，我目前正在这样做:

...but that's not entirely ideal; I'm not happy about updating both lists every time I change my enum. But it's acceptable. Much, much worse is reading XML back in, for which I am currently doing this:

if ([[[anXMLElement childNamed:@"objectType"] stringValue] isEqualToString:@"ETRareObjectType"])
{
    [self initObjectType:ETRareObjectType];
}
else if ([[[anXMLElement childNamed:@"objectType"] stringValue] isEqualToString:@"ETEssentialObjectType"])
{
    [self initObjectType:ETEssentialObjectType];
}
else
{
    [self initObjectType:ETNormalObjectType];
}

呸！这让我很反感.至少必须有一种更简洁的阅读方式，或者也许是一种统一的读写方式?

Yuck! This disgusts me. There's got to be a cleaner way to read, at least, or perhaps a unified way to read and write?

我正在使用 Obj-C 和 Cocoa，但我不介意一些纯 C 函数.如果这是唯一的方法，我什至会使用预处理器.

I'm using Obj-C and Cocoa, but I wouldn't mind some pure C functions. I'd even use preprocessor stuff, if it's the only way.

推荐答案

我没有找到比在字符串中复制枚举更好的方法.但是，我的做法略有不同，即:

I haven't found a better way than duplicating the enum in a string. However, I do it slightly differently, namely:

typedef enum {
    kManipulateWindowTargetFrontWindow,
    kManipulateWindowTargetNamedWindow, 
    kManipulateWindowTargetWindowNameContaining, 
    kManipulateWindowTargetDEFAULT = kManipulateWindowTargetFrontWindow, 
} ManipulateWindowTargetType;
#define kManipulateWindowTargetTypeNamesArray @"FrontWindow", @"NamedWindow", @"WindowNameContaining", nil

然后在实现中:

static NSArray* kManipulateWindowTargetTypeArray = [[NSArray alloc] initWithObjects: kManipulateWindowTargetTypeNamesArray];

NSString* ManipulateWindowTargetTypeToString( ManipulateWindowTargetType mwtt )
{
    return [kManipulateWindowTargetTypeArray objectAtIndex:mwtt];
}

ManipulateWindowTargetType ManipulateWindowTargetTypeFromString( NSString* s )
{
    NSUInteger n = [kManipulateWindowTargetTypeArray indexOfObject:s];
    check( n != NSNotFound );
    if ( n == NSNotFound ) {
        n = kManipulateWindowTargetDEFAULT;
    }
    return (ManipulateWindowTargetType) n;
}

我使用#define 的原因是为了避免在头文件中声明数组，但是将枚举的定义与字符串序列的定义分开是很疯狂的，所以这是我最好的妥协找到了.

The reason I use the #define is to avoid declaring the array in the header file, but it would be insane to separate the definition of the enum from the definition of the sequence of strings, so this is the best compromise I've found.

由于代码是样板文件，您实际上可以将它们设为 NSArray 上的类别.

Since the code is boilerplate, you can actually make them a category on NSArray.

@interface NSArray (XMLExtensions)

- (NSString*) stringWithEnum: (NSUInteger) e;
- (NSUInteger) enumFromString: (NSString*) s default: (NSUInteger) def;
- (NSUInteger) enumFromString: (NSString*) s;

@end

@implementation NSArray (XMLExtensions)

- (NSString*) stringWithEnum: (NSUInteger) e;
{
    return [self objectAtIndex:e];
}

- (NSUInteger) enumFromString: (NSString*) s default: (NSUInteger) def;
{
    NSUInteger n = [self indexOfObject:s];
    check( n != NSNotFound );
    if ( n == NSNotFound ) {
        n = def;
    }
    return n;
}

- (NSUInteger) enumFromString: (NSString*) s;
{
    return [self enumFromString:s default:0];
}


@end

然后:

NSLog( @"s is %@", [kManipulateWindowTargetTypeArray stringWithEnum:kManipulateWindowTargetNamedWindow] );
ManipulateWindowTargetType mwtt = (ManipulateWindowTargetType)[kManipulateWindowTargetTypeArray enumFromString:@"WindowNameContaining" default:kManipulateWindowTargetDEFAULT];
NSLog( @"e is %d", mwtt );

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