Check if multiple strings are empty and print their name - c++

Question

Usually when i want to check if more input stored in a multiple strings are not empty i follow this simple approach:
std::string fieldA = "";
std::string fieldB = "";
std::string fieldC = "Hello";
Now, i can check for all:
if ( fieldA.empty() || fieldB.empty() || fieldC.empty() )
std::cout << "Oh oh.. one or more fields are empty << std::endl;
But it would be nice to know which fields are empty, then, i can write:
if ( fieldA.empty() )
std::cout << "fieldA is empty" << std::endl;
if ( fieldB.empty() )
std::cout << "fieldB is empty" << std::endl;
if ( fieldC.empty() )
std::cout << "fieldC is empty" << std::endl;
But in this way i can discover that fieldA is empty but not the fieldB and in this example i have only three fields, but with more fields?
What is the best practice to managing the control of many strings and locate the empty string?

Answer 1

PaulMcKenzies comment is the one you should follow. But assuming your example is an over simplification of your code, and you can't put all your variables in an array, I think you can be excused if you use a little macro to do stringification for you:
#define PRINT_IF_EMPTY(var) \
do { \
if (var.empty()) \
std::cout << #var " is empty" << std::endl; \
} while(0)
You can now replace your code with this:
PRINT_IF_EMPTY(fieldA);
PRINT_IF_EMPTY(fieldB);
PRINT_IF_EMPTY(fieldC);

Answer 2

You should use a separate FieldValidator class. With that, your code should look like this:
FieldValidator val;
val.requireNotEmpty("field1", field1);
val.requireNotEmpty("field2", field2);
The idea is that all the validation state is kept in one place. I'm sure such a class already exists somewhere since you are not the first to solve this task.

Answer 3

It's better to use container (std::vector, std::list, std::array e.t.c) for similar type of data.
Let's assume you have stored your std::string in std::vector.
std::vector<std::strting> data;
// Now you have to insert std::string in std::vector.
for( int i = 0; i < data.size(); i++) {
if(data[i].empty())
std::cout << "field" << (char)i+65 << " is empty \n";
}

Answer 4

You could use a for-range loop over an initializer list, if printing which field is empty is not mandatory and if you prefer the fields to be distinct variables :
for (const std::string str : {fieldA, fieldB, fieldC})
{
if (str.empty())
{
std::cout << "One or more fields are empty." << std::endl;
break; // Break out of the for loop
}
}