Object creation and destruction flow in C++ - Step-by-Step Execution

Concept Flow - Object creation and destruction flow

Start Program

↓

Call Constructor

↓

Object Created

↓

Use Object

↓

Call Destructor

↓

Object Destroyed

↓

End Program

This flow shows how a C++ object is created by calling its constructor, used, then destroyed by calling its destructor when it goes out of scope.

Execution Sample

C++

#include <iostream>

class MyClass {
public:
  MyClass() { std::cout << "Created\n"; }
  ~MyClass() { std::cout << "Destroyed\n"; }
};

int main() {
  MyClass obj;
  return 0;
}

This code creates an object of MyClass, prints "Created" when constructed, and "Destroyed" when the object goes out of scope at program end.

Execution Table

Step	Action	Output	Object State
1	Enter main function		No object
2	Call MyClass constructor	Created	Object obj created
3	Object obj in use		Object obj alive
4	Exit main function scope		Object obj about to be destroyed
5	Call MyClass destructor	Destroyed	Object obj destroyed
6	Program ends		No object

💡 Program ends after object destruction when main function scope ends

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	Final
obj	Not created	Created	Alive	Destroyed	No object

Key Moments - 3 Insights

Why do we see "Created" before "Destroyed" in the output?

The constructor runs first when the object is created (Step 2), printing "Created". The destructor runs last when the object goes out of scope (Step 5), printing "Destroyed".

When exactly is the destructor called?

The destructor is called automatically when the object goes out of scope, here at the end of main (Step 4 and 5), as shown in the execution_table.

What happens if we create the object inside a block {}?

The object is destroyed as soon as the block ends, calling the destructor immediately after the block, similar to Step 4 and 5.

Visual Quiz - 3 Questions

Look at the execution table, what is the state of 'obj' after Step 3?

A Object obj alive

B Object obj destroyed

C No object

D Object obj about to be destroyed

💡 Hint

Check the 'Object State' column for Step 3 in the execution_table

At which step is the destructor called according to the execution table?

A Step 2

B Step 5

C Step 3

D Step 6

💡 Hint

Look for the action 'Call MyClass destructor' in the execution_table

If we remove the object creation line, what would be the output?

A Only Destroyed

B Only Created

C No output

D Created and Destroyed

💡 Hint

Without object creation, constructor and destructor are not called, so no output lines appear

Concept Snapshot

Object creation calls the constructor.
Object destruction calls the destructor.
Constructor runs when object is made.
Destructor runs when object goes out of scope.
Output shows creation then destruction messages.

Full Transcript

This visual trace shows how a C++ object is created and destroyed. The program starts and enters main. At Step 2, the constructor runs, printing "Created" and creating the object. The object is alive and can be used. When main ends, the object goes out of scope at Step 4, and the destructor runs at Step 5, printing "Destroyed". Finally, the program ends with no objects alive. This flow helps understand when constructors and destructors run automatically in C++.