blocks|key|1422948|text|如果想要将值限制为枚举，则必须创建自定义访问器。因此，首先需要声明一个枚举，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1422949|typedef+enum+{
++++kPaymentFrequencyOneOff+=+0,
++++kPaymentFrequencyYearly+=+1,
++++kPaymentFrequencyMonthly+=+2,
++++kPaymentFrequencyWeekly+=+3
}+PaymentFrequency;|code-block|syntax|javascript|1422950|然后，为你的属性声明getter和setter。覆盖现有的访问器不是一个好主意，因为标准的访问器需要的是NSNumber对象而不是标量类型，如果绑定或KVO系统中的任何内容试图访问您的值，您就会遇到麻烦。|1422951|-+(PaymentFrequency)itemTypeRaw+{
++++return+(PaymentFrequency)[[self+itemType]+intValue];
}

-+(void)setItemTypeRaw:(PaymentFrequency)type+{
++++[self+setItemType:[NSNumber+numberWithInt:type]];
}|1422952|最后，您应该实现%2B+keyPathsForValuesAffecting<Key>，以便在itemType更改时获得itemTypeRaw的KVO通知。|offset|length|style|CODE|1422953|%2B+(NSSet+*)keyPathsForValuesAffectingItemTypeRaw+{
++++return+[NSSet+setWithObject:@"itemType"];
}|1422954|entityMap^0|0|0|0|0|8|X|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@$M|Z|N|10|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

You'll have to create custom accessors if you want to restrict the values to an enum. So, first you'd declare an enum, like so:

<pre><code>typedef enum {
 kPaymentFrequencyOneOff = 0,
 kPaymentFrequencyYearly = 1,
 kPaymentFrequencyMonthly = 2,
 kPaymentFrequencyWeekly = 3
} PaymentFrequency;
</code></pre>

Then, declare getters and setters for your property. It's a bad idea to override the existing ones, since the standard accessors expect an NSNumber object rather than a scalar type, and you'll run into trouble if anything in the bindings or KVO systems try and access your value.

<pre><code>- (PaymentFrequency)itemTypeRaw {
 return (PaymentFrequency)[[self itemType] intValue];
}

- (void)setItemTypeRaw:(PaymentFrequency)type {
 [self setItemType:[NSNumber numberWithInt:type]];
}
</code></pre>

Finally, you should implement <code>+ keyPathsForValuesAffecting&lt;Key&gt;</code> so you get KVO notifications for itemTypeRaw when itemType changes.

<pre><code>+ (NSSet *)keyPathsForValuesAffectingItemTypeRaw {
 return [NSSet setWithObject:@"itemType"];
}
</code></pre>

blocks|key|1423012|text|我正在考虑的另一种方法是根本不声明枚举，而是将值声明为NSNumber上的category方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1423013|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

An alternative approach I'm considering is not to declare an enum at all, but to instead declare the values as category methods on NSNumber.

blocks|key|1423081|text|由于枚举是由标准短整型支持的，因此也不能使用NSNumber包装器并将该属性直接设置为标量值。确保将核心数据模型中的数据类型设置为"Integer+32“。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1423082|MyEntity.h|1423083|typedef+enum+{
kEnumThing,+/*+0+is+implied+*/
kEnumWidget,+/*+1+is+implied+*/
}+MyThingAMaBobs;

@interface+myEntity+:+NSManagedObject

@property+(nonatomic)+int32_t+coreDataEnumStorage;|code-block|syntax|javascript|1423084|代码中的其他地方|1423085|myEntityInstance.coreDataEnumStorage+=+kEnumThing;|1423086|或从JSON字符串解析或从文件加载|1423087|myEntityInstance.coreDataEnumStorage+=+[myStringOfAnInteger+intValue];|1423088|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

Since enums are backed by a standard short you could also not use the NSNumber wrapper and set the property directly as a scalar value. Make sure to set the data type in the core data model as "Integer 32".

MyEntity.h

<pre><code>typedef enum {
kEnumThing, /* 0 is implied */
kEnumWidget, /* 1 is implied */
} MyThingAMaBobs;

@interface myEntity : NSManagedObject

@property (nonatomic) int32_t coreDataEnumStorage;
</code></pre>

Elsewhere in code

<pre><code>myEntityInstance.coreDataEnumStorage = kEnumThing;
</code></pre>

Or parsing from a JSON string or loading from a file

<pre><code>myEntityInstance.coreDataEnumStorage = [myStringOfAnInteger intValue];
</code></pre>

blocks|key|1423119|text|我将属性类型设置为16位整数，然后使用以下代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1423120|#import+<CoreData/CoreData.h>

enum+{
++++LDDirtyTypeRecord+=+0,
++++LDDirtyTypeAttachment
};
typedef+int16_t+LDDirtyType;

enum+{
++++LDDirtyActionInsert+=+0,
++++LDDirtyActionDelete
};
typedef+int16_t+LDDirtyAction;


@interface+LDDirty+:+NSManagedObject

@property+(nonatomic,+strong)+NSString*+identifier;
@property+(nonatomic)+LDDirtyType+type;
@property+(nonatomic)+LDDirtyAction+action;

@end|code-block|syntax|javascript|1423121|..。|1423122|#import+"LDDirty.h"

@implementation+LDDirty

@dynamic+identifier;
@dynamic+type;
@dynamic+action;

@end|1423123|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I set the attribute type as 16 bit integer then use this:

<pre><code>#import &lt;CoreData/CoreData.h&gt;

enum {
 LDDirtyTypeRecord = 0,
 LDDirtyTypeAttachment
};
typedef int16_t LDDirtyType;

enum {
 LDDirtyActionInsert = 0,
 LDDirtyActionDelete
};
typedef int16_t LDDirtyAction;


@interface LDDirty : NSManagedObject

@property (nonatomic, strong) NSString* identifier;
@property (nonatomic) LDDirtyType type;
@property (nonatomic) LDDirtyAction action;

@end
</code></pre>

...

<pre><code>#import "LDDirty.h"

@implementation LDDirty

@dynamic identifier;
@dynamic type;
@dynamic action;

@end
</code></pre>

blocks|key|1208146|text|如果你使用的是mogenerator，看看这个：https://github.com/rentzsch/mogenerator/wiki/Using-enums-as-types。您可以拥有一个名为itemType的整数16属性，在用户信息中的attributeValueScalarType值为Item。然后，在实体的用户信息中，将additionalHeaderFileName设置为定义Item枚举的标头的名称。在生成头文件时，mogenerator会自动将属性设置为Item类型。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1208147|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/rentzsch/mogenerator/wiki/Using-enums-as-types^0|2R|8|3E|O|44|4|4N|O|5G|4|6L|4|O|1T|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]|$9|S|A|T|B|C]|$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@$9|10|A|11|1|12]]|E|$]]|$1|F|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

If you're using mogenerator, have a look at this: <a href="https://github.com/rentzsch/mogenerator/wiki/Using-enums-as-types" rel="noreferrer">https://github.com/rentzsch/mogenerator/wiki/Using-enums-as-types</a>. You can have an Integer 16 attribute called <code>itemType</code>, with a <code>attributeValueScalarType</code> value of <code>Item</code> in the user info. Then, in the user info for your entity, set <code>additionalHeaderFileName</code> to the name of the header that the <code>Item</code> enum is defined in. When generating your header files, mogenerator will automatically make the property have the <code>Item</code> type.

blocks|key|1208245|text|我做了很多这样的事情，我发现下面的表格很有用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1208246|//+accountType
public+var+account:AccountType+{
++++get+{
++++++++willAccessValueForKey(Field.Account.rawValue)
++++++++defer+{+didAccessValueForKey(Field.Account.rawValue)+}
++++++++return+primitiveAccountType.flatMap+{+AccountType(rawValue:+$0)+}+??+.New+}
++++set+{
++++++++willChangeValueForKey(Field.Account.rawValue)
++++++++defer+{+didChangeValueForKey(Field.Account.rawValue)+}
++++++++primitiveAccountType+=+newValue.rawValue+}}
@NSManaged+private+var+primitiveAccountType:+String?|code-block|syntax|javascript|1208247|在本例中，枚举非常简单：|1208248|public+enum+AccountType:+String+{
++++case+New+=+"new"
++++case+Registered+=+"full"
}|1208249|称它为学究，但我使用枚举作为字段名，如下所示：|1208250|public+enum+Field:String+{

++++case+Account+=+"account"
}|1208251|因为对于复杂的数据模型，这可能会很费力，所以我编写了一个代码生成器，它使用MOM+/实体来输出所有映射。我的输入最终是一个从表/行到枚举类型的字典。在此期间，我还生成了JSON序列化代码。我已经为非常复杂的模型做了这件事，结果证明它节省了大量的时间。|1208252|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I have done this a lot and find the following form to be useful:

<pre><code>// accountType
public var account:AccountType {
 get {
 willAccessValueForKey(Field.Account.rawValue)
 defer { didAccessValueForKey(Field.Account.rawValue) }
 return primitiveAccountType.flatMap { AccountType(rawValue: $0) } ?? .New }
 set {
 willChangeValueForKey(Field.Account.rawValue)
 defer { didChangeValueForKey(Field.Account.rawValue) }
 primitiveAccountType = newValue.rawValue }}
@NSManaged private var primitiveAccountType: String?
</code></pre>

In this case, the enum is pretty simple:

<pre><code>public enum AccountType: String {
 case New = "new"
 case Registered = "full"
}
</code></pre>

and call it pedantic, but I use enums for field names, like this:

<pre><code>public enum Field:String {

 case Account = "account"
}
</code></pre>

Since this can get laborious for complex data models, I wrote a code generator that consumes the MOM / entities to spit out all the mappings. My inputs end up being a dictionary from Table/Row to Enum type. While I was at it, I also generated JSON serialization code. I've done this for very complex models and it has turned out to be a big time saver.

What is the best way to bind Core Data entities to enum values so that I am able to assign a type property to the entity? In other words, I have an entity called <code>Item</code> with an <code>itemType</code> property that I want to be bound to an enum, what is the best way of going about this.

Best way to implement Enums with Core Data

JSON

将核心数据实体绑定到枚举值的最佳方式是什么，以便我能够将类型属性分配给实体？换句话说，我有一个名为Item的实体，它有一个itemType属性，我希望将它绑定到一个枚举，最好的方法是什么？

问使用核心数据实现枚举的最佳方法
EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问使用核心数据实现枚举的最佳方法EN

社区

活动

资源

关于

腾讯云开发者

热门产品

热门推荐

更多推荐

问使用核心数据实现枚举的最佳方法
EN