ArduinoJson: API Reference

JsonBuffer::parse()

Description

Parses a JSON input and returns a JsonVariant which can contain an array or an object.

Use this function when you cannot know the type of input at compile-time; otherwise prefer JsonBuffer::parseArray() and JsonBuffer::parseObject().

By design, the parser needs to alter the string to insert null-terminators and replace escaped chars. If the JSON string is read-only, it will have to duplicate the input string, this consume more space in the JsonBuffer. Therefore, it’s recommended to have a JSON input in a char[] or a char*.

Signatures
// The first overload, which accepts a modifiable array of chars, is the most efficient
// since it allows the zero-copy feature.
JsonVariant parse(char* json, uint8_t nestingLimit=10);

// The three following overloads, which accept read-only strings, require a bigger JsonBuffer
// because parts of the JSON input has to be copied.
JsonVariant parse(const char* json, uint8_t nestingLimit=10);
JsonVariant parse(const String& json, uint8_t nestingLimit=10);
JsonVariant parse(const std::string& json, uint8_t nestingLimit=10);

// The two last overloads, which accept input streams, make copy of the input too.
JsonVariant parse(Stream& json, uint8_t nestingLimit=10);
JsonVariant parse(std::istream& json, uint8_t nestingLimit=10);
Arguments

json is the input string to be parsed.

nestingLimit specifies the maximum level of nesting allowed in the JSON string. If set to 0, only a flat array or object can be parsed. If set to 1, the array or object can contain nested arrays or objects but only 1 level deep. And bigger values will allow more level of nesting. The purpose of this feature is to prevent stack overflow that could lead to a security risk.

Return value

Returns a JsonVariant which contains a reference JsonArray or to a JsonObject.

Use JsonVariant::is<T>() to check the type of the value.

Example
char json[] = "[\"hello\",\"world\"]";

StaticJsonBuffer<200> jsonBuffer;
JsonVariant variant = jsonBuffer.parse(json);

if (variant.is<JsonArray>()) // true in this example
{
    JsonArray& array = variant;
    const char* hello = array[0];
    const char* world = array[1];

}
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