Question

Hello I’ve started to learning AS3 from one book and found something I don’t understand.

Ellipse(_board[row][column]).fill = getFill(row, column);

• _board is two dimensional array of Ellipse type, so I just dont understand why is Ellipse(Ellipse object) used when it apparently works without it, or I haven’t seen any changes when I omitted it.

Answer 1

Ellipse(_board[row][column]) is a type cast Type(object)
Because you can push anything into an Array the compiler doesn’t know what kind of objects are stored within the Array. So it is good style to cast objects if you retrive them from an Array to their correct type.

This has several benefits:

• if such an object is not of the type you expect or null, you will know when you typecast instead of getting an error later somewhere far away
• the code executes a bit faster if you are explicit about the types
• if you use a good IDE it can provide you with autocompletion when it knows the types