Returns the number of elements with key key. If ObjectType is the default std::map
type, the return value will always be 0
(key was not found) or 1
(key was found).
- Note
- This method always returns
0
when executed on a JSON type that is not an object.
- Parameters
-
[in] | key | key value of the element to count |
- Returns
- Number of elements with key key. If the JSON value is not an object, the return value will be
0
.
- Complexity
- Logarithmic in the size of the JSON object.
- Example
- The example shows how
count()
is used.
2 #include <nlohmann/json.hpp>
9 json j_object = {{
"one", 1}, {
"two", 2}};
12 auto count_two = j_object.count(
"two");
13 auto count_three = j_object.count(
"three");
16 std::cout <<
"number of elements with key \"two\": " << count_two <<
'\n';
17 std::cout <<
"number of elements with key \"three\": " << count_three <<
'\n';
Output (play with this example online): number of elements with key "two": 1
number of elements with key "three": 0
The example code above can be translated withg++ -std=c++11 -Isingle_include doc/examples/count.cpp -o count
- Since
- version 1.0.0
Definition at line 18581 of file json.hpp.