How to assign a string-variable to a StackString based on the StackString-library?

Question

I'm trying to use the StackString-library which offers not to eat up RAM over time by re-assigning values to strings. I started from scratch and wrote a very basic democode which works. Then I added an assignment to a STackString-variable from a normal string or a function with return-value string See code below If I try to compile I get a compiler-error saying no matching function for call to 'Stack::StackString<50>::append(String&)'

here is the code

#include <StackString.hpp> 
using namespace Stack;  // it is very important to have this line of code. Otherwise the code won't compile

StackString<50> myString = StackString<50>("Hello, World!");

String NormalString = "1234Test";

void setup() 
{ 
  Serial.begin(115200); 
  Serial.println();
  Serial.println();
  Serial.println(myString.c_str());

  myString.prepend("Everybody say: ");
  Serial.println(myString.c_str());

  myString.append(" How are you doing?");
  Serial.println(myString.c_str());
  Serial.println();

  //myString = NormalString;
  myString.append(NormalString);


}

void loop() 
{ // put your main code here, to run repeatedly:

}

Do I have to do some typecasting? and if yes how does it look like? WHat I want to do is assigning a StackString a new value. This means the STackString is on the left side of the "=" assigning operator. I have tried different variants to no avail.

Could this be a problem of the special construction as a "namespace" ? No idea no clue

you find the STackString-library here: https://gitlab.com/arduino-libraries/stackstring

best regards

Stefan

Answer 1

StackString doesn't know what a String is. The append function only accepts a const char *, a const char or an int:

void append(const char* string);
void append(const char character);
void append(int number);

You can get a const char * from a String easily enough with .c_str(), so use that in the append:

myString.append(NormalString.c_str());

There is also no simple assignment (or complete content replacement) with StackString - you have to "clear" the string first. So to replace the content with what is in NormalString you would:

myString.clear();
myString.append(NormalString.c_str());