CODEWITHSUNDEEP
c++stringarduinocharconstants
0288
0288

Reputation: 85

sscanf error: cannot convert 'String' to 'const char*'

I'm trying to extract two numbers separated by a space from a string and save them as two ints. For example:

if input_string = "1 95" then:
servo_choice = 1
input_number = 95

Code:

String input_string = "";
int input_number = 0;
int servo_choice = 0;

input_string = Serial.readString();
sscanf( input_string, "%d %d", &servo_choice, &input_number );

The IDE gives me this error: 

exit status 1
cannot convert 'String' to 'const char*' for argument '1' to 'int scanf(const char*, ...)'

Edit: I guess 

input_number = input_string.substring(1,5).toInt();

Actually works and does what I want. I'd still like to know how to get sscanf to work if possible.

Thanks for any replies in advance..

Upvotes: 3

Views: 2127

Answers (2)

ChatterOne
ChatterOne

Reputation: 3541

The String is a class, not a basic type. That means that you need a method to convert / return a pointer to char if you want to use it in a sscanf. That method exists and it's called c_str() .

So, your line has to be:

sscanf( input_string.c_str(), "%d %d", &servo_choice, &input_number );

Upvotes: 2

DAXaholic
DAXaholic

Reputation: 35368

You could try to convert your String into a char array with toCharArray and pass that to sscanf. Something like that (not tested though)

int buffer_len = input_string.length() + 1;
char buffer[buffer_len];
input_string.toCharArray(buffer, buffer_len);
sscanf(buffer, "%d %d", &servo_choice, &input_number);

Upvotes: 2

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