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Niels Lohmann
08dcdaf9b8
- API pages for operator[], at, front, back, find, contains, count, begin, end, cbegin, cend, items, and type_name of basic_json_view, linked both ways with the basic_json pages - the feature page and size() describe document order and duplicate keys - the examples show when the view helps: reading a few fields of a large text, probing optional members, and members in source order Signed-off-by: Niels Lohmann <mail@nlohmann.me>
1.4 KiB
1.4 KiB
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 the case of a structured type (array or object), a reference to the last element is returned. In the 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
- basic_json_view::back - the same access on a zero-copy view
Version history
- Added in version 1.0.0.
- Adjusted code to return reference to binary values in version 3.8.0.