bool empty() const noexcept;
Checks if a JSON value has no elements (i.e. whether its size()
is 0
).
The return value depends on the different types and is defined as follows:
Value type | return value |
---|---|
null | #!cpp true |
boolean | #!cpp false |
string | #!cpp false |
number | #!cpp false |
binary | #!cpp false |
object | result of function object_t::empty() |
array | result of function array_t::empty() |
No-throw guarantee: this function never throws exceptions.
Constant, as long as array_t
and object_t
satisfy the Container concept; that is, their empty()
functions have constant complexity.
bool empty() const noexcept { return size() == 0; }
This function does not return whether a string stored as JSON value is empty -- it returns whether the JSON container itself is empty which is #!cpp false
in the case of a string.
??? example
The following code uses `empty()` to check if a JSON object contains any elements. ```cpp --8<-- "examples/empty.cpp" ``` Output: ```json --8<-- "examples/empty.output" ```
#!cpp false
for binary types in version 3.8.0.