JsonObject::is<T>()

Description

Tests if the value at specified key has the type T.

Signature

bool is<bool>              (TString key) const;

bool is<const char*>       (TString key) const;
bool is<char*>             (TString key) const;

bool is<double>            (TString key) const;
bool is<float>             (TString key) const;

bool is<signed char>       (TString key) const;
bool is<signed int>        (TString key) const;
bool is<signed long>       (TString key) const;
bool is<signed short>      (TString key) const;
bool is<unsigned char>     (TString key) const;
bool is<unsigned int>      (TString key) const;
bool is<unsigned long>     (TString key) const;
bool is<unsigned short>    (TString key) const;
bool is<signed long long>  (TString key) const;   // <- may require ARDUINOJSON_USE_LONG_LONG
bool is<unsigned long long>(TString key) const;   // <- may require ARDUINOJSON_USE_LONG_LONG

bool is<JsonArray>         (TString key) const;
bool is<JsonObject>        (TString key) const;

Arguments

key: the key of the value in the object, can be a:

const char*,
String,
std::string, or
const __FlashStringHelper*.

T: the type to test.

Return value

true if value at specified key matches the type T,
false if not

Remarks

Different C++ types can store the same JSON value, so is<T>() can return true for several Ts. For example, is<float>() always returns the same value as is<double>() .

The table below gives the correspondence between the JSON type and the C++ types:

JSON type	`T`
Floating point	`float`, `double`
Integer	`int`, `short`, `long`, `long long`
String	`const char`, `char`
Boolean	`bool`
Array	`JsonArray`
Object	`JsonObject`

Caution: is<float>() and is<double>() return true for integers too.

Example

char json[] = "{\"name\":\"toto\",\"pi\":3.14}";
StaticJsonBuffer<256> jsonBuffer;
JsonObject& obj = jsonBuffer.parseObject(json);

bool nameIsString = obj.is<char*>("name"); // <- true
bool piIsFloat = obj.is<float>("pi"); // <- true

// but we could also use JsonVariant.is<T>(), like that:
nameIsString = obj["name"].is<char*>(); // <- true
piIsFloat = obj["pi"].is<float>(); // <- true