Abilities: Drop

删除功能 - 其中最简单的 - 允许忽略或丢弃结构的实例。在许多编程语言中，这种行为被视为默认行为。然而，在Move中，不具备drop能力的结构体是不允许被忽略的。这是 Move 语言的一项安全功能，可确保所有资产得到正确处理。尝试忽略没有删除功能的结构将导致编译错误。

The drop ability - the simplest of them - allows the instance of a struct to be ignored or discarded. In many programming languages this behavior is considered default. However, in Move, a struct without the drop ability is not allowed to be ignored. This is a safety feature of the Move language, which ensures that all assets are properly handled. An attempt to ignore a struct without the drop ability will result in a compilation error.

module book::drop_ability {

    /// This struct has the `drop` ability.
    public struct IgnoreMe has drop {
        a: u8,
        b: u8,
    }

    /// This struct does not have the `drop` ability.
    public struct NoDrop {}

    #[test]
    // Create an instance of the `IgnoreMe` struct and ignore it.
    // Even though we constructed the instance, we don't need to unpack it.
    fun test_ignore() {
        let no_drop = NoDrop {};
        let _ = IgnoreMe { a: 1, b: 2 }; // no need to unpack

        // The value must be unpacked for the code to compile.
        let NoDrop {} = no_drop; // OK
    }
}

删除功能通常用于自定义集合类型，以便在不再需要集合时无需对其进行特殊处理。例如，向量类型具有丢弃能力，允许在不再需要向量时将其忽略。然而，Move的类型系统最大的特点就是能够不掉落。这可确保资产得到正确处理而不是被忽视。

具有单一掉落能力的结构称为见证人。我们在见证和抽象实现部分解释了见证的概念。

The drop ability is often used on custom collection types to eliminate the need for special handling of the collection when it is no longer needed. For example, a vector type has the drop ability, which allows the vector to be ignored when it is no longer needed. However, the biggest feature of Move's type system is the ability to not have drop. This ensures that the assets are properly handled and not ignored.

A struct with a single drop ability is called a Witness. We explain the concept of a Witness in the Witness and Abstract Implementation section.

Types with the drop Ability

Move 中的所有原生类型都具有放置能力。这包括：

All native types in Move have the drop ability. This includes:

• bool
• unsigned integers
• vector
• address

标准库中定义的所有类型也都具有删除功能。这包括：

All of the types defined in the standard library have the drop ability as well. This includes:

• Option
• String
• TypeName