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

   1 # <small>nlohmann::basic_json::</small>count
   2
   3 ```cpp
   4 template<typename KeyT>
   5 size_type count(KeyT&& key) const;
   6 ```
   7
   8 Returns the number of elements with key `key`. If `ObjectType` is the default `std::map` type, the return value will
   9 always be `0` (`key` was not found) or `1` (`key` was found).
  10
  11 ## Template parameters
  12
  13 `KeyT`
  14 :   A type for an object key.
  15
  16 ## Parameters
  17
  18 `key` (in)
  19 :   key value of the element to count.
  20
  21 ## Return value
  22
  23 Number of elements with key `key`. If the JSON value is not an object, the return value will be `0`.
  24
  25 ## Exception safety
  26
  27 Strong exception safety: if an exception occurs, the original value stays intact.
  28
  29 ## Complexity
  30
  31 Logarithmic in the size of the JSON object.
  32
  33 ## Notes
  34
  35 This method always returns `0` when executed on a JSON type that is not an object.
  36
  37 ## Examples
  38
  39 ??? example
  40
  41     The example shows how `count()` is used.
  42
  43     ```cpp
  44     --8<-- "examples/count.cpp"
  45     ```
  46
  47     Output:
  48
  49     ```json
  50     --8<-- "examples/count.output"
  51     ```
  52
  53 ## Version history
  54
  55 - Added in version 1.0.0.