savegame - Unity - How To Save Some Variable WIth PlayerPrefs?

I have a small problem. in the game that I'm creating I created an array of items, each item includes a number of variables (cost, level, etc.). my goal is to save your own variables for each item, with the use of PlayerPrefs. These are my two scripts.

in this first script I create the array called (public Item_Manager [] items;), and in the second script initialize variables for each item dell'aray. I tried to save the values in the second script but then when I open the game again, all items are saved with the same variables.

Therefore, how can I do to save every variable of each item in the array with PlayerPrefs?

The variables are:

public float costo;
public float tickValue;
public float count;

This is the First Script

public class Proiettili_Per_Secondo : MonoBehaviour {

public UnityEngine.UI.Text bpsDisplay;
public Click click;

public Item_Manager[] items;

void Start(){
    StartCoroutine (AutoTick ());
}

void Update (){
    bpsDisplay.text = ConvertiroreProiettili.Instance.GetCurrencyInString 
        (GetPallottoleOgnISecondo (), true, false);
}


public float GetPallottoleOgnISecondo(){
    float tick = 0;
    foreach (Item_Manager item in items) {
        tick += item.count * item.tickValue;
    }
    return tick;
}

public void AutoProiettiliPerSec(){

    click.proiettili += GetPallottoleOgnISecondo () / 10;
}

IEnumerator AutoTick(){
    while (true) {
        AutoProiettiliPerSec();
        yield return new WaitForSeconds(0.10f);
    }
}
}

This is the second script

public class Item_Manager : MonoBehaviour {

public UnityEngine.UI.Text titolo;
public UnityEngine.UI.Text costo_;
public UnityEngine.UI.Text livello;
public UnityEngine.UI.Text valore_da_aggiungere;
public Color standard;
public Color caricamento;

public Click click;
public float costo;
public float tickValue;
public float count;
public string costo_stringa; ///NECESSARIO PER TRASFORAMARE IL VALORE COSTO IN UNO PIU CORTO (K, MILLIOM)
public string itemName;
private float baseCost;
private Slider _slider;

void Start () {

    baseCost = costo;
    _slider = GetComponentInChildren ();
}

void Update () {
    titolo.text = itemName ;
    costo_.text = (costo_stringa = ConvertiroreProiettili.Instance.GetCurrencyInString (costo, false, false));
    livello.text = "Liv: " + count;
    valore_da_aggiungere.text = "+ " + tickValue + "/Sec";


    _slider.value = click.proiettili / costo * 100;
    if (_slider.value >= 100) {
        GetComponent ().color = caricamento;
    } else {
        GetComponent ().color = standard;
    }
}

public void PurchasedItem () {
    if (click.proiettili >= costo) {

        click.proiettili -= costo;
        count += 1;
        costo = Mathf.Round (baseCost * Mathf.Pow(1.50f, count));
    }
}
}

Answer

PlayerPrefs are not designed for saving scores. They are easily modifiable by the end user in a text file. Instead, you should serialize settings, replays, etc. that players have no motivation to hack.

Knowing that, this is how you save to PlayerPrefs:

int Birthday;

void Start ()
{
    Birthday = 172589;
    PlayerPrefs.SetInt ("My Birthday", Birthday);
}

For saving an array, you can serialize it as a string then save the string to PlayerPrefs. I.e.:

//Serializes an int[] into a string then saves it into PlayerPrefs
void SaveIntArray (string Name, int[] IntArray)
{

    string SerializedArray = "";
    string += BytesToString(System.BitConverter.GetBytes (IntArray.Length));
    for (int i = 0; i < IntArray.Length; i++)
    {
        SerializedArray += BytesToString(System.BitConverter.GetBytes(IntArray[i]));
    }
    PlayerPrefs.SetString (Name, SerializedArray);
}

//Gets a string form player prefs and deserializes it as an int[]

int[] GetIntArray (string Name)
{
    string SerializedArray = PlayerPrefs.GetString (Name);
    byte[] SerializedArrayBytes = new byte[SerializedArray.Length]
    for (int i = 0; i < SerializedArray.Length; i++)
    {
        SerializedArrayBytes[i] = (byte)SerializedArray[i];
    }
    int IntArrayLength = BitConverter.ToInt32 (SerializedArrayBytes, 0);
    int[] IntArray = new int[IntArrayLength];


    SerializationPosition = 4;
    for (int i = 0; i < IntArrayLength; i+=1)
    {
        IntArray[i] = BitConverter.ToInt32(SerializedArrayBytes, SerializationPosition);
        SerializationPosition += 4;
    }
}

//Converts an array of bytes to a string

string BytesToString (byte[] bites)
{
   string ret = "";
   for (int i = 0; i < bites.Length; i++)
   {
       ret += (char)bites[i];
   }
}

Alternatively, you can use PlayerPrefsX which has many more such extensions implemented.

If you're making a game for iOS, consider using UnityEngine.Social for saving scores which will save data on a Game Center server that will be unmodifiable except through your game's code.