how to make your health bar go down when a bullet hits your player unity code example

Example: how to make your health bar go down when a bullet hits your player unity

void Update()
    {
        if (Input.GetKeyDown(KeyCode.Space))
        {
            TakeDamage(20);
        }
    }

    void TakeDamage(int damage)
    {
        currentHealth -= damage;

        healthbar.SetHealth(currentHealth);
    }