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.