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# nlohmann::basic_json::find

    // (1)
    iterator find(const typename object_t::key_type& key);
    const_iterator find(const typename object_t::key_type& key) const;

    // (2)
    template<typename KeyType>
    iterator find(KeyType&& key);
    template<typename KeyType>
    const_iterator find(KeyType&& key) const;

1. Finds an element in a JSON object with a key equivalent to `key`. If the element is not found or the JSON value is not an object, `end()` is returned.
2. See 1. This overload is only available if `KeyType` is comparable with `typename object_t::key_type` and `typename object_comparator_t::is_transparent` denotes a type.

## Template parameters

`KeyType`
  A type for an object key other than `json_pointer` that is comparable with `string_t` using `object_comparator_t`. This can also be a string view (C++17).

## Parameters

`key` (in)
  key value of the element to search for.

## Return value

Iterator to an element with a key equivalent to `key`. If no such element is found or the JSON value is not an object, a past-the-end iterator (see `end()`) is returned.

## Exception safety

Strong exception safety: if an exception occurs, the original value stays intact.

## Complexity

Logarithmic in the size of the JSON object.

## Notes

This method always returns `end()` when executed on a JSON type that is not an object.

## Examples

Example: (1) find object element by key

The example shows how `find()` is used.

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

    using json = nlohmann::json;

    int main()
    {
        // create a JSON object
        json j_object = {{"one", 1}, {"two", 2}};

        // call find
        auto it_two = j_object.find("two");
        auto it_three = j_object.find("three");

        // print values
        std::cout << std::boolalpha;
        std::cout << "\"two\" was found: " << (it_two != j_object.end()) << '\n';
        std::cout << "value at key \"two\": " << *it_two << '\n';
        std::cout << "\"three\" was found: " << (it_three != j_object.end()) << '\n';
    }

Output:

    "two" was found: true
    value at key "two": 2
    "three" was found: false

Example: (2) find object element by key using string_view

The example shows how `find()` is used.

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

    using namespace std::string_view_literals;
    using json = nlohmann::json;

    int main()
    {
        // create a JSON object
        json j_object = {{"one", 1}, {"two", 2}};

        // call find
        auto it_two = j_object.find("two"sv);
        auto it_three = j_object.find("three"sv);

        // print values
        std::cout << std::boolalpha;
        std::cout << "\"two\" was found: " << (it_two != j_object.end()) << '\n';
        std::cout << "value at key \"two\": " << *it_two << '\n';
        std::cout << "\"three\" was found: " << (it_three != j_object.end()) << '\n';
    }

Output:

    "two" was found: true
    value at key "two": 2
    "three" was found: false

## See also

- contains checks whether a key exists

## Version history

1. Added in version 3.11.0.
2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0.

Last update: July 31, 2022
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