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nlohmann
44 lines
1.5 KiB
Markdown
44 lines
1.5 KiB
Markdown
# JSON_HAS_FILESYSTEM / JSON_HAS_EXPERIMENTAL_FILESYSTEM
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```cpp
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#define JSON_HAS_FILESYSTEM /* value */
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#define JSON_HAS_EXPERIMENTAL_FILESYSTEM /* value */
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```
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When compiling with C++17, the library provides conversions from and to
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[`std::filesystem::path`](https://en.cppreference.com/w/cpp/filesystem/path). As compiler support for filesystem is
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limited, the library tries to detect whether
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[`<filesystem>`/`std::filesystem`](https://en.cppreference.com/w/cpp/header/filesystem) (`JSON_HAS_FILESYSTEM`) or
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[`<experimental/filesystem>`/`std::experimental::filesystem`](https://en.cppreference.com/w/cpp/header/experimental/filesystem)
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(`JSON_HAS_EXPERIMENTAL_FILESYSTEM`) should be used. To override the built-in check, define `JSON_HAS_FILESYSTEM` or
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`JSON_HAS_EXPERIMENTAL_FILESYSTEM` to `1`.
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## Default definition
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The default value is detected based on the preprocessor macros `#!cpp __cpp_lib_filesystem`,
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`#!cpp __cpp_lib_experimental_filesystem`, `#!cpp __has_include(<filesystem>)`, or
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`#!cpp __has_include(<experimental/filesystem>)`.
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## Notes
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- Note that older compilers or older versions of libstdc++ also require the library `stdc++fs` to be linked to for
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filesystem support.
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- Both macros are undefined outside the library.
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## Examples
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??? example
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The code below forces the library to use the header `<experimental/filesystem>`.
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```cpp
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#define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
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#include <nlohmann/json.hpp>
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...
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```
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## Version history
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- Added in version 3.10.5.
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