static void Main(string[] args)
{
var myEnumerable = new MyEnumerable();
foreach (var item in myEnumerable)
{
Console.WriteLine(item);
}
// MoveNext(position: 0, moveNext: True)
// Current(position: 0, current: 1 kg marhahús)
//1 kg marhahús
// MoveNext(position: 1, moveNext: True)
// Current(position: 1, current: só)
//só
// MoveNext(position: 2, moveNext: True)
// Current(position: 2, current: 1 kg burgonya)
//1 kg burgonya
// MoveNext(position: 3, moveNext: True)
// Current(position: 3, current: 1 kg liszt)
//1 kg liszt
// MoveNext(position: 4, moveNext: False)
//a fordító egy ilyet gyárt:
Console.WriteLine();
Console.WriteLine();
var enumerator = myEnumerable.GetEnumerator();
while (enumerator.MoveNext())
{
var current = enumerator.Current;
//ez lesz a ciklus változója
Console.WriteLine(current);
}
//figyelem, nekünk kell az implementációban azzal foglalkozni,
//ha az adatok megváltoztak !!!
//példa: a List implementációja
//ez a könnyebb megoldás: ha változik a lista, akkor dob egy kivételt.
//a nehezebb: a saját osztályunk gondokodik arról, hogyha változik a belső állapot, akkor a futó
//bejárások ne fussanak hibás helyzetbe
//A List<T> ezt úgy oldja meg, hogy kivételt dob, ha módosítani akarok bejárás közben.
//System.InvalidOperationException: 'Collection was modified; enumeration operation may not execute.'
var shoppingList = new List <string>()
{
"1 kg marhahús", "só", "1 kg burgonya", "1 kg liszt"
};
foreach (var item in shoppingList)
{
shoppingList.Remove(item);
}
Console.ReadLine();
}
static void Main(string[] args)
{
var myEnumerable = new MyEnumerable();
foreach (var item in myEnumerable)
{
Console.WriteLine(item);
}
// MoveNext(position: 0, moveNext: True)
// Current(position: 0, current: 1 kg steak)
//1 kg steak
// MoveNext(position: 1, moveNext: True)
// Current(position: 1, current: salt)
//salt
// MoveNext(position: 2, moveNext: True)
// Current(position: 2, current: 1 kg potato)
//1 kg potato
// MoveNext(position: 3, moveNext: True)
// Current(position: 3, current: 1 kg flour)
//1 kg flour
// MoveNext(position: 4, moveNext: False)
Console.WriteLine();
Console.WriteLine();
// the builder create a code like this:
var enumerator = myEnumerable.GetEnumerator();
while (enumerator.MoveNext())
{
var current = enumerator.Current;
//This is the variable of cycle
Console.WriteLine(current);
}
//Attention, we have to handle with the changes of items in the cycle in the implementation !!!
//example: implementation of a List
//this is the easier solution: if the list changes, it throws an exception.
//this is the toughest solution: our class cares about whether the internal state changes,
//then the running cycle do not run in a bad state
var shoppingList = new List <string>()
{
"1 kg steak", "salt", "1 kg potato", "1 kg flour"
};
foreach (var item in shoppingList)
{ //we delete the items, the List changes ==> it causes a foul (Exception)
//System.InvalidOperationException: 'Collection was modified; enumeration operation may not execute.'
shoppingList.Remove(item);
}
Console.ReadLine();
}