JsonArray::isNull()

Description

JsonArray::isNull() tells whether the JsonArray points to an array or not.

You can use this function to:

1. check if the array was successfully parsed, or
2. check if the array was successfully allocated.

As an alternative, you can use the conversion to bool; for example, if(array) instead of if(!array.isNull())

Signature

bool isNull() const;

Return value

JsonArray::isNull() returns a bool that tells if the JsonArray points to something:

• true if the JsonArray is null,
• false if the JsonArray is valid and points to an array.

Examples

Example 1: parsing success:

StaticJsonDocument<200> doc;
deserializeJson(doc, "[1,2]");
JsonArray array = doc.as<JsonArray>();
Serial.println(array.isNull()); // false

Example 2: parsing failure:

StaticJsonDocument<200> doc;
deserializeJson(doc, "{1,2}");
JsonArray array = doc.as<JsonArray>();
Serial.println(array.isNull()); // true

Example 3: allocation success:

StaticJsonDocument<200> doc;
JsonArray array = doc.to<JsonArray>();
Serial.println(array.isNull()); // false

Example 4: allocation failure:

StaticJsonDocument<1> doc;
JsonArray array = doc.to<JsonArray>();
Serial.println(array.isNull()); // true

See also

• JsonObject::isNull()