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* 🔥 consolidate documentation
* ♻️ overwork std specializations
* 🚚 move images files to mkdocs
* ♻️ fix URLs
* 🔧 tweak MkDocs configuration
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* 📝 document deprecations
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* 🚸 add examples
* 🚧 start adding documentation for macros
* 📝 add note for https://github.com/nlohmann/json/issues/874#issuecomment-1001699139
* 📝 overwork example handling
* 📝 fix Markdown tables

2021-12-29 13:41:01 +01:00

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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

!!! danger

Calling `back` on an empty array or object is undefined behavior and is **guarded by an assertion**!

Examples

??? example

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

Output:

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

Version history

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

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