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56 lines
3.3 KiB
Markdown
56 lines
3.3 KiB
Markdown
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# Supported Macros
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Some aspects of the library can be configured by defining preprocessor macros before including the `json.hpp` header.
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## `JSON_CATCH_USER(exception)`
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This macro overrides `#!cpp catch` calls inside the library. The argument is the type of the exception to catch. As of version 3.8.0, the library only catches `std::out_of_range` exceptions internally to rethrow them as [`json::out_of_range`](../home/exceptions.md#out-of-range) exceptions. The macro is always followed by a scope.
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See [Switch off exceptions](../home/exceptions.md#switch-off-exceptions) for an example.
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## `JSON_NOEXCEPTION`
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Exceptions can be switched off by defining the symbol `JSON_NOEXCEPTION`.
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When defining `JSON_NOEXCEPTION`, `#!cpp try` is replaced by `#!cpp if (true)`,
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`#!cpp catch` is replaced by `#!cpp if (false)`, and `#!cpp throw` is replaced by `#!cpp std::abort()`.
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The same effect is achieved by setting the compiler flag `-fno-exceptions`.
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## `JSON_SKIP_UNSUPPORTED_COMPILER_CHECK`
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When defined, the library will not create a compile error when a known unsupported compiler is detected. This allows to use the library with compilers that do not fully support C++11 and may only work if unsupported features are not used.
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## `JSON_THROW_USER(exception)`
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This macro overrides `#!cpp throw` calls inside the library. The argument is the exception to be thrown. Note that `JSON_THROW_USER` should leave the current scope (e.g., by throwing or aborting), as continuing after it may yield undefined behavior.
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See [Switch off exceptions](../home/exceptions.md#switch-off-exceptions) for an example.
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## `JSON_TRY_USER`
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This macro overrides `#!cpp try` calls inside the library. It has no arguments and is always followed by a scope.
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See [Switch off exceptions](../home/exceptions.md#switch-off-exceptions) for an example.
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## `NLOHMANN_DEFINE_TYPE_INTRUSIVE(type, member...)`
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This macro can be used to simplify the serialization/deserialization of types if (1) want to use a JSON object as serialization and (2) want to use the member variable names as object keys in that object.
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The macro is to be defined inside of the class/struct to create code for. Unlike [`NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE`](#nlohmann_define_type_non_intrusivetype-member), it can access private members.
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The first parameter is the name of the class/struct, and all remaining parameters name the members.
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See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
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## `NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(type, member...)`
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This macro can be used to simplify the serialization/deserialization of types if (1) want to use a JSON object as serialization and (2) want to use the member variable names as object keys in that object.
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The macro is to be defined inside of the namespace of the class/struct to create code for. Private members cannot be accessed. Use [`NLOHMANN_DEFINE_TYPE_INTRUSIVE`](#nlohmann_define_type_intrusivetype-member) in these scenarios.
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The first parameter is the name of the class/struct, and all remaining parameters name the members.
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See [Simplify your life with macros](arbitrary_types.md#simplify-your-life-with-macros) for an example.
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## `NLOHMANN_JSON_SERIALIZE_ENUM(type, ...)`
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This macro simplifies the serialization/deserialization of enum types. See [Specializing enum conversion](enum_conversion.md) for more information.
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