GameObject.Find() in Unity 3D

Question

This is a C# method I found in a Unity3D tutorial:

Public List<Piece> pieces = new List<piece>(); // list of pieces in the pool

public Piece GetPiece(PieceType pt, int visualIndex) {
    Piece p = pieces.Find(x => x.type == pt && x.visualIndex == visualIndex);
} 

What I don't understand is in this line : x => x.type == pt...

Where does the "x" come from and why x.type?

Answer 1

This is List<T>.Find and has nothing to do with GameObject.Find!

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List<T>.Find:

Searches for an element that matches the conditions defined by the specified predicate, and returns the first occurrence within the entire List<T>.

The Predicate<T> is a delegate [(or in your case lambda expression)] to a method that returns true if the object passed to it matches the conditions defined in the delegate. The elements of the current List<T> are individually passed to the Predicate<T> delegate, moving forward in the List<T>, starting with the first element and ending with the last element. Processing is stopped when a match is found.

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Then what you have there is a Lambda Expression where x is the iterator variable like in

foreach(var x in pieces)

that is where the x comes from. It can basically called whatever you like. And its type is Piece so it depends on your Piece implementation what x.type is .. looking on your parameters I'ld say it is an enum called PieceType.

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So it does basically the same as and is just a shorthand for

public Piece GetPiece(PieceType pt, int visualIndex) 
{
    foreach(var x in pieces)
    {
        if(x.type == pt && x.visualIndex == visualIndex) return x;
    }

    return default;
}