New macros for the named JSON convertor generation #4563
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the correct maximum number of member variables is 63
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I see several PRs that can potentially conflict with this one (#4528, #4560), and I'd rather not do extra work in maintaining this patch, if it's going to be pointless anyway. @nlohmann can you at least tell what are the chances of accepting this PR? There is an unsuccessful check in the static code analysis, but first, it's a false positive, it says that the three fields are not used, when they most definitely are, and second, it's in example files, which shouldn't be statically analysed in the first place. Examples should be demonstrative and clear, not statically correct. |
| - The `NON_INTRUSIVE` macros should be defined inside the namespace of the class/struct to create code for and thus doesn't have access to the private fields, the `INTRUSIVE` is to be defined inside the class/struct. | ||
| - The `WITH_DEFAULT` macros should be used when not all fields are required to be present in the JSON, the ones without `WITH_DEFAULTS` will raise an exception if the fields are missing. | ||
| - The `ONLY_SERIALIZE` macros should be used if you only want the `to_json` function to be created. This option excludes the `WITH_DEFAULT` variant since it is only applicable to `from_json`. | ||
| - The `WITH_NAMES` macros should be used if you want custom names for you JSON fields, the ones without `WITH_NAMES` will use the member names for JSON fields. |
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| In both macros, the first parameter is the name of the class/struct, and all remaining parameters name the members. | ||
| For all the macros, the first parameter is the name of the class/struct, and all remaining parameters name the members. The `DERIVED` variants require additional second argument for the parent class. |
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The DERIVED part should probably go before "all remaining"
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| #define NLOHMANN_JSON_TO(v1) nlohmann_json_j[#v1] = nlohmann_json_t.v1; | ||
| #define NLOHMANN_JSON_FROM(v1) nlohmann_json_j.at(#v1).get_to(nlohmann_json_t.v1); | ||
| #define NLOHMANN_JSON_FROM_WITH_DEFAULT(v1) nlohmann_json_t.v1 = nlohmann_json_j.value(#v1, nlohmann_json_default_obj.v1); | ||
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| #define NLOHMANN_JSON_TO_WITH_NAME(v1, v2) nlohmann_json_j[v1] = nlohmann_json_t.v2; | ||
| #define NLOHMANN_JSON_FROM_WITH_NAME(v1, v2) nlohmann_json_j.at(v1).get_to(nlohmann_json_t.v2); | ||
| #define NLOHMANN_JSON_FROM_WITH_DEFAULT_WITH_NAME(v1, v2) nlohmann_json_t.v2 = nlohmann_json_j.value(v1, nlohmann_json_default_obj.v2); |
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This will need to be updated with the new null handling.
This patch adds several new
NLOHMANN_DEFINE_<***>_WITH_NAMESmacros. They behave the same way as the ones withoutWITH_NAMES, but require explicit JSON names. Useful for the situation when the fields in the class are following the naming convention that you do not want to expose to JSON, e.g.or if the name in JSON cannot be used as the field name because it is reserved, e.g.
Also, this patch includes the unit tests for the new macros, and the update for the documentation.
It also fixes a small error in the docs where the
DEFINE_TYPEmacros were said to support up to 64 member variables, when in reality it is 63.This is the update to the #4092 which didn't pass the amalgamation test because I had an old version of astyle. I updated the patch to include the new
DERIVEDvariations as well asONLY_SERIALIZE. Hopefully this one will be better.Pull request checklist
Read the Contribution Guidelines for detailed information.
include/nlohmanndirectory, runmake amalgamateto create the single-header filessingle_include/nlohmann/json.hppandsingle_include/nlohmann/json_fwd.hpp. The whole process is described here.