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55 lines
1.2 KiB
Markdown
55 lines
1.2 KiB
Markdown
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# basic_json::emplace_back
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```cpp
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template<class... Args>
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reference emplace_back(Args&& ... args);
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```
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Creates a JSON value from the passed parameters `args` to the end of the JSON value. If the function is called on a JSON
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`#!json null` value, an empty array is created before appending the value created from `args`.
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## Template parameters
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`Args`
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: compatible types to create a `basic_json` object
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## Parameters
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`args` (in)
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: arguments to forward to a constructor of `basic_json`
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## Return value
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reference to the inserted element
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## Exceptions
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Throws [`type_error.311`](../../home/exceptions.md#jsonexceptiontype_error311) when called on a type other than JSON
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array or `#!json null`; example: `"cannot use emplace_back() with number"`
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## Complexity
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Amortized constant.
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## Examples
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??? example
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The example shows how `emplace_back()` can be used to add elements to a JSON array. Note how the `null` value was
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silently converted to a JSON array.
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```cpp
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--8<-- "examples/emplace_back.cpp"
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```
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Output:
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```json
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--8<-- "examples/emplace_back.output"
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```
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## Version history
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- Since version 2.0.8.
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- Returns reference since 3.7.0.
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