使用C ++类中的复杂函数初始化const成员 [英] Initialize const members using complex function in C++ class

问题描述

我有一个与3d网格一起工作的程序。这个网格有自己的类对象Grid，看起来像这样（简化版本）：

I have a program that works with 3d grids. This grid has its own class object Grid that looks like this (simplified version):

class Grid
{
  public:
    Grid() { readDataFromInputFile(); }
  private:
    void readDataFromInputFile() {...} // this function reads the values for i, j, k from disk
    int i; int j; int k;
};

现在我想做的是能够设置变量i，j和k作为const int，以避免他们意外地在其他函数中混乱。但我不能轻易地将它们设置在成员初始化列表中，因为它们必须从文件读取。我已经浏览了现有的讨论，但是我找不到关于这个问题的准确讨论。

What I would like to do now, is to be able to set the variables i, j and k as const int, to avoid messing them accidentally up in the other functions. I can however not easily set them in a member initializer list, because they have to be read from file. I have been browsing through the existing discussions but I couldn't find an accurate discussion on this problem.

有一个解决方案能够设置为const，仍然能够使用复杂的函数来检索数据吗？

Is there a solution to be able to set them as const, and still be able to use a complex function to retrieve the data? In my real application, there are of course much more variables to be read, that are not allowed to change after initialization.

推荐答案

在我的实际应用程序中，有更多的变量要读取，不要破坏一个责任原则： Grid 不应负责从文件加载自身，这是另一个组件的责任（例如一个简单的加载函数） ：

Don't break the One Responsibility Principle: A Grid should not be responsible of loading itself from a file, this is a responsibility of another component (For example a simple loading function):

class Grid
{
public:
    Grid( int ii , int jj , int kk ) : i{ ii } , j{ jj } , k{ kk }
private:
    const int i , j , k;
};

Grid loadGrid( constd std::string& filename )
{
    ...
};

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