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>
67 lines
1.4 KiB
Markdown
67 lines
1.4 KiB
Markdown
# <small>nlohmann::basic_json::</small>back
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```cpp
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reference back();
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const_reference back() const;
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```
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Returns a reference to the last element in the container. For a JSON container `c`, the expression `c.back()` is
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equivalent to
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```cpp
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auto tmp = c.end();
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--tmp;
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return *tmp;
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```
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## Return value
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In the case of a structured type (array or object), a reference to the last element is returned. In the case of number,
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string, boolean, or binary values, a reference to the value is returned.
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## Exception safety
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Strong guarantee: if an exception is thrown, there are no changes in the JSON value.
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## Exceptions
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If the JSON value is `#!json null`, exception
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[`invalid_iterator.214`](../../home/exceptions.md#jsonexceptioninvalid_iterator214) is thrown.
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## Complexity
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Constant.
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## Notes
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!!! info "Precondition"
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The array or object must not be empty. Calling `back` on an empty array or object yields undefined behavior.
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## Examples
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??? example
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The following code shows an example for `back()`.
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```cpp
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--8<-- "examples/back.cpp"
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```
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Output:
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```json
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--8<-- "examples/back.output"
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```
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## See also
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- [front](front.md) to access the first element
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- [basic_json_view::back](../basic_json_view/back.md) - the same access on a zero-copy view
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## Version history
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- Added in version 1.0.0.
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- Adjusted code to return reference to binary values in version 3.8.0.
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