I'm very new to C++ and struggling to figure out how I should iterate through a list of objects and access their members.
I've been trying this where data is a std::list and Student a class.
std::list<Student>::iterator<Student> it;
for (it = data.begin(); it != data.end(); ++it) {
std::cout<<(*it)->name;
}
and getting the following error:
error: base operand of ‘->’ has non-pointer type ‘Student’
You're close.
std::list<Student>::iterator it;
for (it = data.begin(); it != data.end(); ++it){
std::cout << it->name;
}
Note that you can define it inside the for loop:
for (std::list<Student>::iterator it = data.begin(); it != data.end(); ++it){
std::cout << it->name;
}
And if you are using C++11 then you can use a range-based for loop instead:
for (auto const& i : data) {
std::cout << i.name;
}
Here auto automatically deduces the correct type. You could have written Student const& i instead.
std::cout<<(*it).name; and std::cout<<it->name; will work, right? Iterator can be regarded as pointer to the element.Since C++ 11, you could do the following:
for(const auto& student : data)
{
std::cout << student.name << std::endl;
}
const mandatory in range-based loop or is avoiding it a bad habbit?
std::vector<T>::size_type, which is 2^64 / sizeof(T) (that is, the maximum number of objects that can be represented in the address space of memory. This is also why you shouldn't use STL containers to replace database in some situations.If you add an #include <algorithm> then you can use the for_each function and a lambda function like so:
for_each(data.begin(), data.end(), [](Student *it)
{
std::cout<<it->name;
});
You can read more about the algorithm library at https://en.cppreference.com/w/cpp/algorithm
and about lambda functions in cpp at https://learn.microsoft.com/en-us/cpp/cpp/lambda-expressions-in-cpp?view=vs-2019
It is also worth to mention, that if you DO NOT intent to modify the values of the list, it is possible (and better) to use the const_iterator, as follows:
for (std::list<Student>::const_iterator it = data.begin(); it != data.end(); ++it){
// do whatever you wish but don't modify the list elements
std::cout << it->name;
}
cbegin() and cend().-> it works like pointer u don't have to use *
for( list<student>::iterator iter= data.begin(); iter != data.end(); iter++ )
cout<<iter->name; //'iter' not 'it'
