I'm studying the example datecalc.ino from the RTClib library
https://github.com/adafruit/RTClib
I'm stumped almost at once by this unfamiliar line:
void showDate(const char* txt, const DateTime& dt)
I understand the asterisk to be a 'pointer'. But what does the second parameter mean? IOW, how should I 'read' it? Preferably in 'Arduino programmer' terms?
From research so far I suspect that may be a big ask. If so I'll just have to accept it's C++ stuff, and copy/paste on trust to proceed with my project.
Here's the full code:
// Simple date conversions and calculations
#include "RTClib.h"
void showDate(const char* txt, const DateTime& dt) {
Serial.print(txt);
Serial.print(' ');
Serial.print(dt.year(), DEC);
Serial.print('/');
Serial.print(dt.month(), DEC);
Serial.print('/');
Serial.print(dt.day(), DEC);
Serial.print(' ');
Serial.print(dt.hour(), DEC);
Serial.print(':');
Serial.print(dt.minute(), DEC);
Serial.print(':');
Serial.print(dt.second(), DEC);
Serial.print(" = ");
Serial.print(dt.unixtime());
Serial.print("s / ");
Serial.print(dt.unixtime() / 86400L);
Serial.print("d since 1970");
Serial.println();
}
void showTimeSpan(const char* txt, const TimeSpan& ts) {
Serial.print(txt);
Serial.print(" ");
Serial.print(ts.days(), DEC);
Serial.print(" days ");
Serial.print(ts.hours(), DEC);
Serial.print(" hours ");
Serial.print(ts.minutes(), DEC);
Serial.print(" minutes ");
Serial.print(ts.seconds(), DEC);
Serial.print(" seconds (");
Serial.print(ts.totalseconds(), DEC);
Serial.print(" total seconds)");
Serial.println();
}
void setup () {
Serial.begin(115200);
#ifndef ESP8266
while (!Serial); // wait for serial port to connect. Needed for native USB
#endif
DateTime dt0 (0, 1, 1, 0, 0, 0);
showDate("dt0", dt0);
DateTime dt1 (1, 1, 1, 0, 0, 0);
showDate("dt1", dt1);
DateTime dt2 (2009, 1, 1, 0, 0, 0);
showDate("dt2", dt2);
DateTime dt3 (2009, 1, 2, 0, 0, 0);
showDate("dt3", dt3);
DateTime dt4 (2009, 1, 27, 0, 0, 0);
showDate("dt4", dt4);
DateTime dt5 (2009, 2, 27, 0, 0, 0);
showDate("dt5", dt5);
DateTime dt6 (2009, 12, 27, 0, 0, 0);
showDate("dt6", dt6);
DateTime dt7 (dt6.unixtime() + 3600); // One hour later.
showDate("dt7", dt7);
DateTime dt75 = dt6 + TimeSpan(0, 1, 0, 0); // One hour later with TimeSpan addition.
showDate("dt7.5", dt75);
DateTime dt8 (dt6.unixtime() + 86400L); // One day later.
showDate("dt8", dt8);
DateTime dt85 = dt6 + TimeSpan(1, 0, 0, 0); // One day later with TimeSpan addition.
showDate("dt8.5", dt85);
DateTime dt9 (dt6.unixtime() + 7 * 86400L); // One week later.
showDate("dt9", dt9);
DateTime dt95 = dt6 + TimeSpan(7, 0, 0, 0); // One week later with TimeSpan addition.
showDate("dt9.5", dt95);
DateTime dt10 = dt6 + TimeSpan(0, 0, 42, 42); // Fourty two minutes and fourty two seconds later.
showDate("dt10", dt10);
DateTime dt11 = dt6 - TimeSpan(7, 0, 0, 0); // One week ago.
showDate("dt11", dt11);
TimeSpan ts1 = dt6 - dt5;
showTimeSpan("dt6-dt5", ts1);
TimeSpan ts2 = dt10 - dt6;
showTimeSpan("dt10-dt6", ts2);
}
void loop () {
}
