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C++ initialize const strings in class?

Posted on 2014-01-25
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Last Modified: 2014-01-25
Say I have a class with a lot of constant strings in it:
#pragma once
class ClassA
{
public:
  ClassA(void);
  ~ClassA(void);
private:
  const std::wstring textA;
  const std::wstring textB;
  const std::wstring textC;
  ...
  const std::wstring textZ;
};

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How can I instantiate this class and fill in all the strings, especially if this class is initialized in the constructor initializer list of another class?
#pragma once
#include "ClassA.h"

class ClassB
{
public:
  ClassB(void);
  ~ClassB(void);
private:
  ClassA a;
};

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0
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Question by:deleyd
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4 Comments
 
LVL 32

Expert Comment

by:phoffric
ID: 39809387
Add the constructor to initialize the constants:
   ClassA(std::wstring tA) : textA(tA), textB(tA), textC(tA), textZ(tA) {}
   ClassB(std::wstring bA) : a(bA) {}

This makes them all the same. Customize to your needs.
0
 
LVL 32

Expert Comment

by:phoffric
ID: 39809410
If those constants are the same for all instances of ClassA, then you should make them static. If you do that, you can define their values in the corresponding .cpp file. In this case, you would not include them in the constructor.
0
 

Author Comment

by:deleyd
ID: 39809473
Each class will have different constants.

I'm going to end up with:

ClassA(std::wstring tA,
std::wstring tB,
std::wstring tC,
...
std::wstring tD) : textA(tA), textB(tB), textC(tC),... textZ(tZ) {}

And the initializer is going to look even worse. Plus I'm discovering problems in the initializer are difficult to debug. The debugger stops but doesn't tell me where in this huge list the problem is.
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LVL 32

Accepted Solution

by:
phoffric earned 2000 total points
ID: 39809526
Create a struct to hold the constant values (but don't make them const in the struct). Add a constructor to take in the struct, and the constructor will load the struct into a const struct.
struct Constants {
  std::wstring textA;
  std::wstring textB;
  std::wstring textC;
  std::wstring textZ;
};

class ClassA
{
public:
   ClassA(void) {}
   ClassA(Constants myConst) : myConstants(myConst) {}
   ~ClassA(void) {}
private:
   const Constants myConstants;
};

class ClassB
{
public:
   ClassB(void) {}
   ClassB(Constants bA) : a(bA) {}
   ~ClassB(void) {}
private:
  ClassA a;
};


int main() {
   Constants tempNonConstValues;
   // ... fill in non-const local constants
   ClassB cb(tempNonConstValues);
}

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