What am I doing wrong with the input function? - c++

Question

So for my second C++ class, we have to write a program that creates an array of 5 structs and a class. In the struct is an int, an array of 5 doubles, and a character array of 81 elements. Of course one of the functions is to take in information from the user. That function is called setStructData() :
void Prog1Class::setStructData()
{
for(int i=0; i<5; i++)
{
cout<<"input an integer, five doubles, and a character array up to 80 characters."<<endl;
cin>>StructArray[i].m_iVal;
for(int j=0; j<5; j++)
{
cin>>StructArray[i].m_dArray[j];
}
cin.ignore('\n');
cin>>StructArray[i].m_sLine;
cout<<"String entered: "<<StructArray[i].m_sLine<<endl;
}
}
The next function getStructData() is to take each element in the array of structs and cout to the user the element on one line, the next element on the next line and so on and so on until all 5 elements on the array are shown. This is what I have:
void Prog1Class::getStructData(int index, Prog1Struct *struct_ptr)
{
struct_ptr=&StructArray[index];
cout<<struct_ptr->m_iVal<<" ";
for(int i=0; i<5; i++)
{
cout<<struct_ptr->m_dArray[i]<<" ";
}
cout<<struct_ptr->m_sLine<<endl;
}
This program works when I enter by keyboard input (which is inputting for each element in the structarray on one line), but my professor has given us a text file test.txt that we're supposed to use and it looks like this (with the character array on a different line than the rest):
10 1.2 2.3 3.4 4.5 5.6
Test string 1
20 2.3 3.4 4.5 5.6 6.7
Test string 2
30 3.4 4.5 5.6 6.7 7.8
Test string 3
40 4.5 5.6 6.7 7.8 8.9
Test string 4
50 5.6 6.7 7.8 8.9 9.1
Test string 5
Its the text file that's screwing my program up because it has the character array on a totally different line. I believe its just the way I'm inputting the data, but I don't know how to fix it. Could anybody help me?
When I use I/O redirection to use the test.txt file to input my data, I get it to output back the first line (without the string) and then the rest is a bunch of crazy junk. Please help me!d

Answer 1

First off, you should always verify that your input was successful! That is, always check after reading that the stream is still in good state, e.g.:
if (!(std::cin >> StructArray[i].m_dArray[j])) {
std::cout << "failed to read double value\n";
}
Next, when using the formatted input into character array, you shall always first set the width! Without setting the width you create an attack vector into your program which can be hacked (it may not matter for your homework assignment but once you create professional software it may very well matter):
if (!(std::cin >> std::setw(sizeof(StructArray[i].m_sLine)) >> StructArray[i].m_sLine)) {
std::cout << "failed to read string\n";
}
Note, however, that the formatted input always stops reading at the first whitespace character. The input from the file seems to contain strings of the form Test string which would result in Test being read and string being left in the stream for the next item to be read. You can use getline() to read all input until the end of the line. However, since all the formatted input operations tend to leave space characters, e.g., the newline after the numbers, in the stream you should probably read leading whitespace. For example, you could use
if (!(std::cin >> std::ws).getline(StructArray[i].m_sLine, sizeof(StructArray[i].m_sLine)) {
...
}
Personally, I would prefer to use std::getline(std::cin >> std::ws, str) with the second argument being of type std::string but it seems your assignment doesn't allow the use of the std::string class. The manipulator std::ws reads all leading whitespace.