std::any是C 17引入的類型安全容器，可存儲(chǔ)任意類型的單個(gè)值，需包含頭文件；支持通過賦值或初始化存入不同類型的值，使用std::any_cast安全訪問，支持異常和指針形式的類型檢查，結(jié)合has_value和type可判斷值存在性與類型信息，適用於配置系統(tǒng)等異構(gòu)類型場(chǎng)景，但存在性能開銷且要求存儲(chǔ)類型可複制，建議謹(jǐn)慎使用以保持代碼清晰與效率。

std::any is a type-safe container introduced in C 17 that can hold a single value of any type. It's part of the \ header and is useful when you need to store heterogeneous types in a uniform way — for example, in containers or function return values where the exact type isn't known at compile time.

Include the Required Header

To use std::any , include the \ header:

Create and Assign Values

You can create an std::any object and assign values of different types to it. The assignment replaces the current value.

You can also initialize directly:

Access the Stored Value

To retrieve the value stored in an std::any , use std::any_cast . This is type-safe: if the requested type doesn't match, it throws std::bad_any_cast .

You can also use pointer-style casting to avoid exceptions:

Check and Manage Type Safety

You can check whether an std::any contains a value using has_value() , and get its type with type() , which returns a const std::type_info& .

This is helpful when debugging or validating input from generic interfaces.

Use Cases and Limitations

std::any is ideal for scenarios like configuration systems, plugin interfaces, or message passing where types vary. However, it comes with overhead — both in performance and safety. Overuse can make code harder to maintain and debug.

Avoid storing large objects by value; prefer wrapping them in smart pointers if needed:

Also, note that types stored in std::any must be copy-constructible.

Basically, std::any gives flexibility with runtime type erasure, but should be used thoughtfully to preserve clarity and performance.

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