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# nlohmann::basic_json::max_size

    size_type max_size() const noexcept;

Returns the maximum number of elements a JSON value is able to hold due to system or library implementation limitations, i.e. `std::distance(begin(), end())` for the JSON value.

## Return value

The return value depends on the different types and is defined as follows:

Value type | return value
--- | ---
null | `0` (same as `size()`)
boolean | `1` (same as `size()`)
string | `1` (same as `size()`)
number | `1` (same as `size()`)
binary | `1` (same as `size()`)
object | result of function `object_t::max_size()`
array | result of function `array_t::max_size()`

## Exception safety

No-throw guarantee: this function never throws exceptions.

## Complexity

Constant, as long as `array_t` and `object_t` satisfy the Container concept; that is, their `max_size()` functions have constant complexity.

## Notes

This function does not return the maximal length of a string stored as JSON value -- it returns the maximal number of string elements the JSON value can store which is `1`.

## Examples

Example

The following code calls `max_size()` on the different value types.

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

    using json = nlohmann::json;

    int main()
    {
        // create JSON values
        json j_null;
        json j_boolean = true;
        json j_number_integer = 17;
        json j_number_float = 23.42;
        json j_object = {{"one", 1}, {"two", 2}};
        json j_array = {1, 2, 4, 8, 16};
        json j_string = "Hello, world";

        // call max_size()
        std::cout << j_null.max_size() << '\n';
        std::cout << j_boolean.max_size() << '\n';
        std::cout << j_number_integer.max_size() << '\n';
        std::cout << j_number_float.max_size() << '\n';
        std::cout << j_object.max_size() << '\n';
        std::cout << j_array.max_size() << '\n';
        std::cout << j_string.max_size() << '\n';
    }

Output:

    0
    1
    1
    1
    115292150460684697
    576460752303423487
    1

Note the output is platform-dependent.

## Version history

- Added in version 1.0.0.
- Extended to return `1` for binary types in version 3.8.0.

Last update: July 29, 2022
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