在 英语 中使用 An enum 的示例及其翻译为 中文
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How can you enumerate an enum in C?
An enum is a type that the developer can define.
This is because when defining an enum….
Listing 7-12: Designating an enum as public makes all its variants public.
Here's how our Elvis example looks as an enum:.
The possible values of an enum type are usually referred to as enum constants.
For example, Python has no enum block,but it does have an enum module:.
The size of an ENUM object is determined by the number of different enumeration values.
Another tier, such as ARCHIVE,can be added using an enum called StorageType.
The first is a type tag- an enum- that identifies what data type is being stored.
Item 3: Enforce the singleton property with a private constructor or an enum type.
DO NOT use an enum for open setssuch as the operating system version, names of your friends.
Technically, an enum is considered to be a special kind of class, but that is not important for now.
By blocking all single digit labels, the root of an ENUM tree cannot be placed directly in. tel.
An enum always has an underlying type, which may be any of the integral types, except for char.
First, we will define and use an enum to show how an enum can encode meaning along with data.
CONSIDER using Int32(the default in most programming languages)as the underlying type of an enum unless any of the following is true:.
In Rust they can be an enum(Rust's keyword for a"tagged union" or"sum type"):.
If an ENUM column is declared NOT NULL, its default value is the first element of the list of allowed values.
Listing 15-2: The first attempt at defining an enum to represent a cons list data structure of i32 values.
An enum type, provided it has public accessibility and the types in which it is nested(if any) also have public accessibility(§17.2).
For example, here is the denition of an enum type named Season whose values are the names of the four seasons of the year:.
Using an enum plus a match expression means that Rust will ensure at compile time that every possible case is handled, as discussed in Chapter 6.
Let's look at another example of an enum in Listing 6-2: this one has a wide variety of types embedded in its variants:.
If a field has an enum type, the parser will recognize symbolic enum values(with or without quotes) instead of numbers, e.g. field: EnumVal.
The first name in an enum has value 0, the next 1, and so on, unless explicit values are specified.
The associated value of an enum member may not, directly or indirectly, use the value of its own associated enum member.
For some text fields, such as"province" or"sex",we can define them as a ENUM type.