Struct vs class

Learn the memory difference between struct and class.

The struct and class difference

A struct is a value type; its value is stored directly and it usually sits on the stack. A class is a reference type; its object is kept on the heap and only the reference sits in the variable. This difference directly affects memory usage.

public struct Nokta
{
    public int x;
    public int y;
}

The Nokta above is a value type.

Which type to choose?

For small and frequently copied data a struct is suitable; this way no heap allocation is made. For large objects or ones that need inheritance a class is used. Choosing the right type prevents needless allocations.

public class Nesne
{
    public int x;
}
// Nokta is a value type, Nesne is a reference type

The smaller the data, the more a struct makes sense.

Exercise Work with a struct

In the Start method of the class StructOrnek, create a variable of type Nokta and assign the value 2 to its x field. Print the text "Nokta x: " joined with the x field using Debug.Log. Also define the Nokta structure with its x field as a value type.

Show example solution

using UnityEngine;

public class StructOrnek : MonoBehaviour
{
    void Start()
    {
        Nokta n = new Nokta();
        n.x = 2;
        Debug.Log("Nokta x: " + n.x);
    }
}

public struct Nokta
{
    public int x;
}

Test yourself

What is the main memory difference between struct and class?
- struct does not use memory
- struct is stored on the heap, class on the stack
- struct is stored as a value type, a class object sits on the heap
- Both are always stored on the heap
Show answer

struct is stored as a value type, a class object sits on the heap — A struct carries its value directly; a class variable references the object on the heap.

Define the value type with struct

    public ____ Nokta
    {
        public int x;
    }

Show answer

    public struct Nokta
    {
        public int x;
    }

Memory type terms

struct

A value type
class

A reference type
Değer tipi

The value is stored directly
Referans tipi

It points to the object on the heap

Next lesson: Object pooling revisited

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