DynamicConverter

`folly/DynamicConverter.h`

When dynamic objects contain data of a known type, it is sometimes useful to have its well-typed representation. A broad set of type-conversions are contained in DynamicConverter.h, and facilitate the transformation of dynamic objects into their well-typed format.

Usage

Simply pass a dynamic into a templated convertTo:

    dynamic d = { { , ,  }, { ,  } }; // a vector of vector of int

    auto vvi = convertTo<fbvector<fbvector<int>>>(d);

Supported Types

convertTo naturally supports conversions to

arithmetic types (such as int64_t, unsigned short, bool, and double)
fbstring, std::string
containers and map-containers

NOTE:

convertTo will assume that Type is a container if

it has a Type::value_type, and
it has a Type::iterator, and
it has a constructor that accepts two InputIterators

Additionally, convertTo will assume that Type is a map if

it has a Type::key_type, and
it has a Type::mapped_type, and
value_type is a pair of const key_type and mapped_type

If Type meets the container criteria, then it will be constructed by calling its InputIterator constructor.

Customization

If you want to use convertTo to convert dynamics into your own custom class, then all you have to do is provide a template specialization of DynamicConverter with the static method convert. Make sure you put it in namespace folly.

Example:

    struct Token {

      int kind_;

      fbstring lexeme_;

      explicit Token(int kind, const fbstring& lexeme)

        : kind_(kind), lexeme_(lexeme) {}

    };

    namespace folly {

    template <> struct DynamicConverter<Token> {

      static Token convert(const dynamic& d) {

        int k = convertTo<int>(d["KIND"]);

        fbstring lex = convertTo<fbstring>(d["LEXEME"]);

        return Token(k, lex);

      }

    };

    }

巴特西

DynamicConverter

`folly/DynamicConverter.h`

Usage

Supported Types

Customization

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