- Qt 5.15
- Qt Core
- C++ Classes
- QStack
- Qt 5.15.19 Reference Documentation

# QStack Class

template <typename T> class QStack

The QStack class is a template class that provides a stack. More...

Header: | #include <QStack>
qmake: | QT += core
Inherits: | QVector

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Functions

T | pop()
void | push(const T &t)
void | swap(QStack<T> &other)
T & | top()
const T & | top() const

## Detailed Description

QStack<T> is one of Qt's generic container classes. It implements a stack data structure for items of a same type.

A stack is a last in, first out (LIFO) structure. Items are added to the top of the stack using push() and retrieved from the top using pop(). The top() function provides access to the topmost item without removing it.

Example:

         QStack<int> stack;
         stack.push(1);
         stack.push(2);
         stack.push(3);
         while (!stack.isEmpty())
             cout << stack.pop() << Qt::endl;

The example will output 3, 2, 1 in that order.

QStack inherits from QVector. All of QVector's functionality also applies to QStack. For example, you can use isEmpty() to test whether the stack is empty, and you can traverse a QStack using QVector's iterator classes (for example, QVectorIterator). But in addition, QStack provides three convenience functions that make it easy to implement LIFO semantics: push(), pop(), and top().

QStack's value type must be an assignable data type. This covers most data types that are commonly used, but the compiler won't let you, for example, store a QWidget as a value; instead, store a QWidget *.

See also QVector and QQueue.

## Member Function Documentation

### T QStack::pop()

Removes the top item from the stack and returns it. This function assumes that the stack isn't empty.

See also top(), push(), and isEmpty().

### void QStack::push(const T &t)

Adds element t to the top of the stack.

This is the same as QVector::append().

See also pop() and top().

### void QStack::swap(QStack<T> &other)

Swaps stack other with this stack. This operation is very fast and never fails.

This function was introduced in Qt 4.8.

### T &QStack::top()

Returns a reference to the stack's top item. This function assumes that the stack isn't empty.

This is the same as QVector::last().

See also pop(), push(), and isEmpty().

### const T &QStack::top() const

This is an overloaded function.

See also pop() and push().