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nlohmann
68 lines
1.6 KiB
Markdown
68 lines
1.6 KiB
Markdown
# <small>nlohmann::</small>operator""_json
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```cpp
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json operator ""_json(const char* s, std::size_t n);
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json operator ""_json(const char8_t* s, std::size_t n); // since C++20
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```
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This operator implements a user-defined string literal for JSON objects. It can be used by adding `#!cpp _json` to a
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string literal and returns a [`json`](json.md) object if no parse error occurred.
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It is recommended to bring the operator into scope using any of the following lines:
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```cpp
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using nlohmann::literals::operator ""_json;
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using namespace nlohmann::literals;
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using namespace nlohmann::json_literals;
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using namespace nlohmann::literals::json_literals;
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using namespace nlohmann;
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```
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This is suggested to ease migration to the next major version release of the library. See
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[`JSON_USE_GLOBAL_UDLS`](macros/json_use_global_udls.md#notes) for details.
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## Parameters
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`s` (in)
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: a string representation of a JSON object
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`n` (in)
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: length of string `s`
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## Return value
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[`json`](json.md) value parsed from `s`
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## Exceptions
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The function can throw anything that [`parse(s, s+n)`](basic_json/parse.md) would throw.
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## Complexity
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Linear.
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## Examples
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??? example
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The following code shows how to create JSON values from string literals.
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```cpp
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--8<-- "examples/operator_literal_json.cpp"
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```
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Output:
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```json
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--8<-- "examples/operator_literal_json.output"
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```
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## See also
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- [Creating JSON values](../features/creating_values.md) - the article on creating JSON values
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## Version history
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- Added in version 1.0.0.
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- Moved to namespace `nlohmann::literals::json_literals` in 3.11.0.
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- Added `char8_t*` overload in 3.12.x.
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