Creating an array of structs in C++

Question

I'm working on an assignment that requires me to use an "array of structs". I did this once before for another assignment for this prof, using this code:

struct monthlyData {
    float rainfall;
    float highTemp; 
    float lowTemp;  
    float avgTemp;  
} month[12];

Which got the job done fine, but I got points marked off for the array being global. What should I do instead to avoid that? I haven't touched C++ at all over the summer, so I'm pretty rusty on it at the moment and have no clue where to start for this one.

Solution 1

Simply define the struct as:

struct monthlyData {
    float rainfall;
    float highTemp; 
    float lowTemp;  
    float avgTemp;  
};

And then create an array of this struct, in a function, where you need it:

void f() {
    monthlyData month[12];
    //use month
}

Now the array is not a global variable. It is a local variable, and you've to pass this variable to other function(s) so that other function(s) can use the same array. And here is how you should pass it:

void otherFunction(monthlyData *month) {
    // process month
}

void f() {
    monthlyData month[12];
    // use month
    otherFunction(month);
}

Note that otherFunction assumes that the size of array is 12 (a constant value). If the size can be anything, then you can do this instead:

void otherFunction(monthlyData *month, int size) {
    // process month
}

void f() {
    monthlyData month[12];
    // use month
    otherFunction(month, 12); //pass 12 as size
}

Solution 2

well, you can have the array declared only inside the method that needs it :)

struct monthlyData
{
  float rainfall;
  float highTemp; 
  float lowTemp;  
  float avgTemp;  
};

int main()
{

  monthlyData month[12];

}

and if you need to use it also from another method, you pass it around as method parameter.