ceph/src/jaegertracing/opentelemetry-cpp/third_party/nlohmann-json/doc/mkdocs/docs/api/basic_json/emplace_back.md

   1 # <small>nlohmann::basic_json::</small>emplace_back
   2
   3 ```cpp
   4 template<class... Args>
   5 reference emplace_back(Args&& ... args);
   6 ```
   7
   8 Creates a JSON value from the passed parameters `args` to the end of the JSON value. If the function is called on a JSON
   9 `#!json null` value, an empty array is created before appending the value created from `args`.
  10
  11 ## Template parameters
  12
  13 `Args`
  14 :   compatible types to create a `basic_json` object
  15
  16 ## Parameters
  17
  18 `args` (in)
  19 :   arguments to forward to a constructor of `basic_json`
  20
  21 ## Return value
  22
  23 reference to the inserted element
  24
  25 ## Exceptions
  26
  27 Throws [`type_error.311`](../../home/exceptions.md#jsonexceptiontype_error311) when called on a type other than JSON
  28 array or `#!json null`; example: `"cannot use emplace_back() with number"`
  29
  30 ## Complexity
  31
  32 Amortized constant.
  33
  34 ## Examples
  35
  36 ??? example
  37
  38     The example shows how `emplace_back()` can be used to add elements to a JSON array. Note how the `null` value was
  39     silently converted to a JSON array.
  40
  41     ```cpp
  42     --8<-- "examples/emplace_back.cpp"
  43     ```
  44
  45     Output:
  46
  47     ```json
  48     --8<-- "examples/emplace_back.output"
  49     ```
  50
  51 ## Version history
  52
  53 - Since version 2.0.8.
  54 - Returns reference since 3.7.0.