Arduino; dynamically getting elements of array; Array is of type struct which includes different size strings

Question

in Arduino C++ I have the following struct:

struct acceptedCommand {
 String Command;
 int   switchcase;
};

Then I initialise an Array of the above struct like this:

const acceptedCommand acceptedCommands[] = { 
  {"set-amountofcells", 1}, 
  {"set-cell-min-voltage", 2},
  {"set-cell-max-voltage", 7}
  ...
};

Desired result: I want to dynamically return the number of elements in this array.

What I already tried: I cannot use the SizeOf function because this returns only the total amount of bytes used of the array.

I also cannot divide the value returned by SizeOf by the size of the struct because the size of each element of the array is different (because of the different length of the string).

So how can I get the number of elements in the acceptedCommands[] array dynamically?

Killzone Kid · Accepted Answer · 2018-12-21 07:40:15Z

1

sizeof(acceptedCommands)/sizeof(acceptedCommand) should give you the number of structs in the array, thus the number of commands.

You might think your struct is variable size but it is not, sizeof String is known at compile time even if the length of its char array is different, because String will be an object probably containing a pointer to char array among other things and sizeof pointer is known at compile time.

edited Dec 21, 2018 at 7:40

answered Dec 21, 2018 at 5:48

Killzone Kid

6,2703 gold badges20 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

John Ranger Over a year ago

+1 - you are right - this gives back the correct amount of array entries. Thanks for correcting my wrong thinking :-)

thilinaur · Accepted Answer · 2018-12-21 04:37:07Z

0

You'll need to use vectors instead of arrays. Use Standard C++ for Arduino. Then you'll be able to use stl vector in Arduino.

answered Dec 21, 2018 at 4:37

thilinaur

1417 bronze badges

Collectives™ on Stack Overflow

Arduino; dynamically getting elements of array; Array is of type struct which includes different size strings

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related