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nlohmann
2026-10-04 09:47:40 +00:00
parent ba443db2af
commit 19f538472d
9 changed files with 376 additions and 275 deletions
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@@ -79,6 +79,7 @@ Some important things:
* When using `get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.)
* In function `from_json`, use function [`at()`](../api/basic_json/at.md) to access the object values rather than `operator[]`. In case a key does not exist, `at` throws an exception that you can handle, whereas `operator[]` exhibits undefined behavior.
* You do not need to add serializers or deserializers for STL types like `std::vector`: the library already implements these.
* If you control the type, consider defining `to_json`/`from_json` as `friend` functions inside the class ("hidden friends"). Argument-dependent lookup then only finds them for your type, which also avoids a [GCC < 11 compilation error](../home/faq.md#incomplete-detector-type-with-gcc-11).
??? example "Example: serialize a `person` to JSON with `to_json`"
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@@ -78,6 +78,7 @@ Some important things:
- When using `get<your_type>()`, `your_type` **MUST** be [DefaultConstructible](https://en.cppreference.com/w/cpp/named_req/DefaultConstructible). (There is a way to bypass this requirement described later.)
- In function `from_json`, use function [`at()`](https://json.nlohmann.me/api/basic_json/at/index.md) to access the object values rather than `operator[]`. In case a key does not exist, `at` throws an exception that you can handle, whereas `operator[]` exhibits undefined behavior.
- You do not need to add serializers or deserializers for STL types like `std::vector`: the library already implements these.
- If you control the type, consider defining `to_json`/`from_json` as `friend` functions inside the class ("hidden friends"). Argument-dependent lookup then only finds them for your type, which also avoids a [GCC < 11 compilation error](https://json.nlohmann.me/home/faq/#incomplete-detector-type-with-gcc-11).
Example: serialize a `person` to JSON with `to_json`