nlohmann::basic_json::back

reference back();

const_reference back() const;

Returns a reference to the last element in the container. For a JSON container c, the expression c.back() is equivalent to

auto tmp = c.end();
--tmp;
return *tmp;

Return value

In case of a structured type (array or object), a reference to the last element is returned. In case of number, string, boolean, or binary values, a reference to the value is returned.

Exception safety

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

Exceptions

If the JSON value is #!json null, exception invalid_iterator.214 is thrown.

Complexity

Constant.

Notes

!!! info “Precondition”

The array or object must not be empty. Calling `back` on an empty array or object yields undefined behavior.

Examples

??? example

The following code shows an example for `back()`.
 
```cpp
--8<-- "examples/back.cpp"
```

Output:

```json
--8<-- "examples/back.output"
```

See also

• front to access the first element

Version history

• Added in version 1.0.0.
• Adjusted code to return reference to binary values in version 3.8.0.