Saving enum values into a dictionary

问题

How does one save an enum value to a dictionary?

When I try the following

enum someEnum
{
    field0 = 0,
    field1 = 1,
    field2 = 2,
};

enum someEnum someEnumObject;

and I try to save it to a dictionary using

[NSDictionary dictionaryWithObjectsAndKeys:]

someEnumObject, @"enum", 

I get this

warning: Semantic Issue: Incompatible integer to pointer conversion sending 'enum behaviour' to parameter of type 'id'

回答1:

Use the following to save it to dictionary,

[NSNumber numberWithInt:enumValue], @"enum",

And you can retrieve it as,

enumValue = [[dictionary valueForKey:@"enum"] intValue];

回答2:

Better use NSNumber literals to convert an enum to an object so that it can be stored in NSDictionary:

[NSDictionary dictionaryWithObjectsAndKeys:@(someEnumObject), @"enum", nil];

Literals provide shorthands to write stuff, this dictionary can be written like:

@{@"enum":@(someEnumObject)};

Read more about literals here: http://clang.llvm.org/docs/ObjectiveCLiterals.html

回答3:

An enum is essentially an integer and an NSDictionary stores objects, so you need to convert your enum to an object. An NSNumber would work well for this:

[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInt:someEnumObject], @"enum", nil];

回答4:

In modern times @(enumValue) is the easier approach.

来源：https://stackoverflow.com/questions/6663686/saving-enum-values-into-a-dictionary