teensy4.0 linux18.04 compilation calss vector init

[LaurentDelaon]

Hi
sort presentation :

class a_classe {
std::vector<double>  m_A
}

and try to this in loop:

...
a_classe the_class
...
the_class.m_A= {1,2};

Compile but seemnot afect values to vector m_A

Another way :

class a_classe {
std::vector<double>  m_A

void afunction(){
the_class.m_A= {1,2};
}

}

works fine but not convenient because definition is hard coded the class can only have an only one instantiation/definition.

How can do to do it out of class definition?
Thank's Laurent.

[PaulStoffregen]

Please show complete programs. Even if the rest of the code is trivial, it is much easier to answer if we can copy the code into Arduino and run on a Teensy without the work of adding (guessing) the missing lines.

[LaurentDelaon]

I put this code sample for fun...

Because when I test it to verify that my post sample doesn't works it is work fine...
The only difference is is that I putit in a .h .cpp files...
So I do compare with the original code.
Sorry for these troubles...

#include <vector>



class Un_rst

{
    public:
    std::vector<double>  m_A;
    double compute();  
    
 
};

double Un_rst::compute()
{
  Serial.println();
    for (unsigned i = 0; i <= m_A.size() - 1; i++) {Serial.print("m_A: "); Serial.print(m_A[i],5);} ;
  Serial.println();
};




Un_rst theRst;


void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);//USB
   while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }
  //
  
}

void loop() {
  // put your main code here, to run repeatedly:
  theRst.m_A={1,2,3};
  theRst.compute();
}