Verifying that inputs are in range - c++

Question

I'm having a problem implementing this.. the program is meant to take date input in the format dd.mm.yyyy, it does that already but I've been trying to add the code that checks
if the date is more than 31 or February is more than 28
if the month is more than 12
It should return an error since the input is incorrect
And also if a user start input with . then the program shouldn't allow more than 2 inputs of .. so that the user can just just go back with the arrow buttons and type in the correct input
#include "examplevalidator.h"
ExampleValidator::ExampleValidator(QObject* parent)
: QValidator (parent)
{
}
ExampleValidator::~ExampleValidator()
{
}
QValidator::State ExampleValidator::validate( QString & input, int & pos ) const
{
if (input.isEmpty()) return Intermediate;
bool ok;
QString str;
str = input[pos-1];
if(input.size() == 10
&& ((input[2] == '.'))
&& ((input[5] == '.'))
&& input[0].isDigit()
&& input[1].isDigit() && (input.toInt(&ok, 10) <= 31)
&& input[3].isDigit()
&& input[4].isDigit() && (input.toInt(&ok, 10) <= 12)
&& input[6].isDigit()
&& input[7].isDigit()
&& input[8].isDigit()
&& input[9].isDigit() && (input.toInt(&ok, 10) <= 2020)
// && (pos == 1 )&& (input.toInt(&ok, 10) <= 3)
// && (pos == 2 )&& (input.toInt(&ok, 10) <= 31)
)
return Acceptable;
if(input.size() > 10)
return Invalid;
if((pos == 1 )&& (input.toInt(&ok, 10) <= 3) && input[0].isDigit())
{return Intermediate;}
if((pos == 2) && (input.toInt(&ok, 10) <= 31) && input[pos-1].isDigit())
{return Intermediate;}
if((pos == 3) && (input.toInt(&ok, 10) <= 1) && input[pos-1].isDigit())
{return Intermediate;}
if((pos == 4) && (input.toInt(&ok, 10) <= 1) && input[3].isDigit())
{return Intermediate;}
if((pos == 5) && (input.toInt(&ok, 10) <= 12) && input[4].isDigit())
{return Intermediate;}
// if((pos == 6) && (input.toInt(&ok, 10) <= 999999) && input[pos-1].isDigit())
// {return Intermediate;}
if((pos == 7) && (input.toInt(&ok, 10) <= 9) && input[6].isDigit())
{return Intermediate;}
if((pos == 8) && (input.toInt(&ok, 10) <= 99) && input[7].isDigit())
{return Intermediate;}
if((pos == 9) && (input.toInt(&ok, 10) <= 999) && input[8].isDigit())
{return Intermediate;}
if((pos == 10) && (input.toInt(&ok, 10) < 99999) && input[9].isDigit())
{return Intermediate;}
if (input[0] == '.' )
{return Intermediate;}
if(pos > 1)
{
if (input.isEmpty()) return Intermediate;
if((pos > 1) || (pos <=2 ) && (input[pos-1] == '.'))
return Intermediate;
if(pos > 8 && pos <= 10 && input[pos-1].isDigit())
{return Intermediate;}
else {return Invalid;}
}
}

Answer 1

You can use a regular expression to validate dd.mm.yyyy
Have a look at https://regex101.com/ for trying them out.
Something like the code below should get you started
#include <regex>
std::smatch match;
const std::regex ddmmyyyyRegExp(R"((([0-9]{2})\.([0-9]{2})\.([0-9]{4})))");
std::string dd;
std::string mm;
std::string yyyy;
if (std::regex_search(input, match, ddmmyyyyRegExp) && match.size() == 4)
{
dd= match.str(1);
mm= match.str(2);
yyyy= match.str(3);
}

Answer 2

I've been able to fix the code, but still I'm unable to check if the inputs are in a particular range. I'm trying to check if the date limit isn't more than 31 and month isn't greater than 12
ExampleValidator::ExampleValidator(QObject* parent)
: QValidator (parent)
{
}
ExampleValidator::~ExampleValidator()
{
}
QValidator::State ExampleValidator::validate( QString & input, int & pos ) const
{
if (input.isEmpty()) return Intermediate;
bool ok;
QString str;
str = input[pos-1];
if(pos > 0 && input[0] != '.')
{
if (input.isEmpty()) return Intermediate;
if(((pos == 1 )&& (input.toInt(&ok, 10) <= 9) && input[0].isDigit() && input.size() != 10))
{return Intermediate;}
if(((pos == 2) && (input.toInt(&ok, 10) <= 99) && input[1].isDigit() && input.size() != 10))
{return Intermediate;}
if(((pos == 3) && (input.toInt(&ok, 10) <= 999)) && (input[2].isDigit() || input[2] == '.') && input.size() != 10)
{return Intermediate;}
if((pos == 4) && (input.toInt(&ok, 10) <= 9999) && input[3].isDigit() && input.size() != 10)
{return Intermediate;}
if((pos == 5) && (input.toInt(&ok, 10) <= 99999) && input[4].isDigit() && input.size() != 10)
{return Intermediate;}
if(((pos == 6) && (input.toInt(&ok, 10) <= 999999)) && (input[5].isDigit() || input[5] == '.') && input.size() != 10)
{return Intermediate;}
if((pos == 7) && (input.toInt(&ok, 10) <= 99999999) && input[6].isDigit() && input.size() != 10)
{return Intermediate;}
if((pos == 8) && (input.toInt(&ok, 10) <= 999999999) && input[7].isDigit() && input.size() != 10)
{return Intermediate;}
if((pos == 9) && (input.toInt(&ok, 10) <= 999999999) && input[8].isDigit() && input.size() != 10)
{return Intermediate;}
if((pos == 10) && (input.toInt(&ok, 10) < 2020) && input[9].isDigit() && input[2] == '.' && input[5]=='.' )
{
return Acceptable;}
}
if(((pos == 1) && (input[0] == '.')) || ((pos == 2) && (input[1] == '.')))
{
return Intermediate;
}
else if (input.isEmpty()) {return Intermediate;}
}```