Inner classes: Difference between revisions
C++ entry
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* [[Classes]]
<br>
=={{header|C++}}==
C++ supports nested/inner classes. There is no difference but the term '''nested''' is more common.
<syntaxhighlight lang="cpp">#include <iostream>
#include <vector>
class Outer
{
int m_privateField;
public:
// constructor for Outer class
Outer(int value) : m_privateField{value}{}
// define a nested class
class Inner
{
int m_innerValue;
public:
// constructor for Inner class
Inner(int innerValue) : m_innerValue{innerValue}{}
// adds the values from the outer and inner class objects
int AddOuter(Outer outer) const
{
// a nested class has access to the private members of the outer class
return outer.m_privateField + m_innerValue;
}
};
};
int main()
{
// a nested class can be constructed like any other class; it does not
// need an instance of the outer class
Outer::Inner inner{42};
// create an outer class and pass it to the inner class
Outer outer{1};
auto sum = inner.AddOuter(outer);
std::cout << "sum: " << sum << "\n";
// a common usage of nested types is for containers to define their iterators
std::vector<int> vec{1,2,3};
std::vector<int>::iterator itr = vec.begin();
std::cout << "vec[0] = " << *itr << "\n";
}
</syntaxhighlight>
{{out}}
<pre>sum: 43
vec[0] = 1
</pre>
=={{header|Wren}}==
Strictly speaking, Wren does not support inner classes.
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