What does the double colon represent?

Projects Programming
1

Does the double colon in the snippet of code below (last line) represent a pointer?
Am I reading this correctly that key is a pointer to the MIFARE_Key in the instance of the class?

#include <MFRC522.h>

constexpr uint8_t RST_PIN = 5;        // Same as const byte RST_PIN
constexpr uint8_t SS_PIN = 4;
const int LEDPIN = 10;                    // NodeMCU SD3 (GPIO10)


MFRC522 rfid(SS_PIN, RST_PIN);    // Create an instance of the class
MFRC522::MIFARE_Key key;
2

No, and no.

MFRC522::MIFARE_Key key;

is closer to

key is declared to be of type MIFARE_Key as defined in MFRC522.o

:: is the C++ scope resolution operator. Don't you have access to Google or a similar search service?

3

vaj4088:
No, and no.

MFRC522::MIFARE_Key key;

is closer to

key is declared to be of type MIFARE_Key as defined in MFRC522.o

:: is the C++ scope resolution operator. Don't you have access to Google or a similar search service?

LOL- You try googling "::".

But, now that I know what to look for... Thanks.

4

LOL

5

I used Bing.com and searched for

C++ ::

and achieved many hits. YMMV

6

vaj4088:
No, and no.

MFRC522::MIFARE_Key key;

is closer to

key is declared to be of type MIFARE_Key as defined in MFRC522.o

key is declared to be of type MIFARE_Key as defined in MFRC522.o the definition of the class MFRC522.

Regards,
Ray L.

7

What RayLivingston wrote is more accurate and I agree with him.

8

vaj4088:
I used Bing.com and searched for

C++ ::

and achieved many hits. YMMV

I don't think that is what Bing is for :grinning:

9

Metallor:
I don't think that is what Bing is for :grinning:

Maybe not, but it worked for me.

10

This is now the top Google answer for "arduino double colon", and links back to the Google search...a niche web-crawler trap indeed!