Information Technology Reference
In-Depth Information
// Immutable: A copy is made at construction.
public struct
PhoneList2
{
private readonly
Phone
[] phones;
public
PhoneList2(
Phone
[] ph)
{
phones =
new
Phone
[ph.Length];
// Copies values because Phone is a value type.
ph.CopyTo(phones,
0
);
}
public
IEnumerable
<
Phone
> Phones
{
get
{
return
phones;
}
}
}
Phone
[] phones2 =
new
Phone
[
10
];
// initialize phones
PhoneList
p2 =
new
PhoneList
(phones);
// Modify the phone list:
// Does not modify the copy in pl.
phones2[
5
] =
Phone
.GeneratePhoneNumber();
Yo u n e e d t o f o l l o w t h e s a m e r u l e s w h e n y o u r e t u r n a m u t a b l e r e f e r e n c e
type. If you add a property to retrieve the entire array from the PhoneList
struct, that accessor would also need to create a defensive copy. See Item
27 for more details.
The complexity of a type dictates which of three strategies you will use to
initialize your immutable type. The Address structure defined one con-
structor to allow clients to initialize an address. Defining the reasonable set
of constructors is often the simplest approach.
Yo u c a n a l s o c r e a t e f a c t o r y m e t h o d s t o i n i t i a l i z e t h e s t r u c t u r e . F a c t o r i e s
make it easier to create common values. The .NET Framework Color type
