json/api/basic_json/begin/index.md

nlohmann::basic_json::begin

iterator begin() noexcept;
const_iterator begin() const noexcept;

Returns an iterator to the first element.

begin() points to the first element and end() to the position after the last element; the dashed cell is the past-the-last position, which must not be dereferenced.

Return value

iterator to the first element

Exception safety

No-throw guarantee: this member function never throws exceptions.

Complexity

Constant.

Examples

Example

The following code shows an example for begin().

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

using nlohmann::json;

int main()
{
    // create an array value
    json array = {1, 2, 3, 4, 5};

    // get an iterator to the first element
    json::iterator it = array.begin();

    // serialize the element that the iterator points to
    std::cout << *it << '\n';
}

Output:

1

See also

• end - returns an iterator to one past the last element
• cbegin - returns a const iterator to the first element
• rbegin - returns a reverse iterator to the last element
• items - returns an iteration proxy to access keys and values during range-based for loops
• Iterators - the article on iterators
• basic_json_view::begin - the same iteration on a zero-copy view (in document order, not sorted by key)

Version history

• Added in version 1.0.0.