Skip to content

# nlohmann::basic_json::array

    static basic_json array(initializer_list_t init = {});

Creates a JSON array value from a given initializer list. That is, given a list of values `a, b, c`, creates the JSON value `[a, b, c]`. If the initializer list is empty, the empty array `[]` is created.

## Parameters

`init` (in)
  initializer list with JSON values to create an array from (optional)

## Return value

JSON array value

## Exception safety

Strong guarantee: if an exception is thrown, there are no changes in the JSON value.

## Complexity

Linear in the size of `init`.

## Notes

This function is only needed to express two edge cases that cannot be realized with the initializer list constructor (`basic_json(initializer_list_t, bool, value_t)`). These cases are:

1. creating an array whose elements are all pairs whose first element is a string -- in this case, the initializer list constructor would create an object, taking the first elements as keys
2. creating an empty array -- passing the empty initializer list to the initializer list constructor yields an empty object

## Examples

Example

The following code shows an example for the `array` function.

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

    using json = nlohmann::json;

    int main()
    {
        // create JSON arrays
        json j_no_init_list = json::array();
        json j_empty_init_list = json::array({});
        json j_nonempty_init_list = json::array({1, 2, 3, 4});
        json j_list_of_pairs = json::array({ {"one", 1}, {"two", 2} });

        // serialize the JSON arrays
        std::cout << j_no_init_list << '\n';
        std::cout << j_empty_init_list << '\n';
        std::cout << j_nonempty_init_list << '\n';
        std::cout << j_list_of_pairs << '\n';
    }

Output:

    []
    []
    [1,2,3,4]
    [["one",1],["two",2]]

## See also

- `basic_json(initializer_list_t)` - create a JSON value from an initializer list
- `object` - create a JSON object value from an initializer list

## Version history

- Added in version 1.0.0.

Back to top