删除c ++程序中的全局变量

Question

I have a large program in c++ having too many function and global variables. Now, I want to remove those global variables and I want to use only local variables rather than global variables. Can any one suggest me the best way to do this. Thanks!

Its around 4000 lines program in C++. There are 10 classes and 60 functions in those different classes, 30 global variables. The global variables have used between functions of different classes.

Answer 1

I normally start by putting the global variables in a namespace

namespace global
{
  int var;
  ...
}

this will cause you to get errors everwhere that 'var' is used, then i would just replace the references one by one to the namespace variant. once all global variable references are in the namespace it is easier to see which variables are local and which are global

if ( global::var == 1 ) ...

now by searching global::var you get a list of variables where it is used then you would need to go through the usage case by case to see if a variable is used in several modules or not, in those cases you may need to pass it in as a function argument in other cases declare it is a local variable.

its a cumbersome method but eliminating global vars is always worth doing.

Answer 2

I suggest a solution such as removing their declarations from global scope and put them in the appreciated functions.

Examlpe:

int hello; // global
// remove it

Now, put it in the function:

void func()
{
   int hello; // local
  //...

We have two cases:

If some other function needs to know the value of hello , let it take that hello as a parameter:

void func2(const int &helloVar)
{
   // ...

If a global variable is used only by a single function, you can use a static local variable instead..

Answer 3

I would suggest using a class. They are perfect for hiding variables and functions into one group and categorizing. Here is the basic structure:

class example
{
public:
    example(); //basic constructor
    int function1();  //example function
    int x;  // a variable accesible globally
private:
    int y;  // a variable only accesible by functions of the class
};

Calling each function is easy but I wont explain since I dont want to start a text wall. You can go to this link for more information: http://www.cplusplus.com/doc/tutorial/classes/

Answer 4

你可以把那些变量放在aclass中，然后在第一个位置创建指向该类对象的指针，然后使用那些变量然后将这个指针传递给每个需要那些变量的方法，不要忘记在不使用时删除对象。