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# nlohmann::basic_json::get_to

    template<typename ValueType>
    ValueType& get_to(ValueType& v) const noexcept(
        noexcept(JSONSerializer<ValueType>::from_json(
            std::declval<const basic_json_t&>(), v)));

Explicit type conversion between the JSON value and a compatible value. The value is filled into the input parameter by calling the `json_serializer<ValueType>` `from_json()` method.

The function is equivalent to executing

    ValueType v;
    JSONSerializer<ValueType>::from_json(*this, v);

This overload is chosen if:

- `ValueType` is not `basic_json`,
- `json_serializer<ValueType>` has a `from_json()` method of the form `void from_json(const basic_json&, ValueType&)`

## Template parameters

`ValueType`
  the value type to return

## Return value

the input parameter, allowing chaining calls

## Exceptions

Depends on what `json_serializer<ValueType>` `from_json()` method throws

## Examples

Example

The example below shows several conversions from JSON values to other types. There a few things to note: (1) Floating-point numbers can be converted to integers, (2) A JSON array can be converted to a standard `std::vector<short>`, (3) A JSON object can be converted to C++ associative containers such as `#cpp std::unordered_map<std::string, json>`.

    #include <iostream>
    #include <unordered_map>
    #include <nlohmann/json.hpp>

    using json = nlohmann::json;

    int main()
    {
        // create a JSON value with different types
        json json_types =
        {
            {"boolean", true},
            {
                "number", {
                    {"integer", 42},
                    {"floating-point", 17.23}
                }
            },
            {"string", "Hello, world!"},
            {"array", {1, 2, 3, 4, 5}},
            {"null", nullptr}
        };

        bool v1;
        int v2;
        short v3;
        float v4;
        int v5;
        std::string v6;
        std::vector<short> v7;
        std::unordered_map<std::string, json> v8;

        // use explicit conversions
        json_types["boolean"].get_to(v1);
        json_types["number"]["integer"].get_to(v2);
        json_types["number"]["integer"].get_to(v3);
        json_types["number"]["floating-point"].get_to(v4);
        json_types["number"]["floating-point"].get_to(v5);
        json_types["string"].get_to(v6);
        json_types["array"].get_to(v7);
        json_types.get_to(v8);

        // print the conversion results
        std::cout << v1 << '\n';
        std::cout << v2 << ' ' << v3 << '\n';
        std::cout << v4 << ' ' << v5 << '\n';
        std::cout << v6 << '\n';

        for (auto i : v7)
        {
            std::cout << i << ' ';
        }
        std::cout << "\n\n";

        for (auto i : v8)
        {
            std::cout << i.first << ": " << i.second << '\n';
        }
    }

Output:

    1
    42 42
    17.23 17
    Hello, world!
    1 2 3 4 5

    string: "Hello, world!"
    number: {"floating-point":17.23,"integer":42}
    null: null
    boolean: true
    array: [1,2,3,4,5]

## Version history

- Since version 3.3.0.

Last update: May 1, 2022
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