zetbox/ForDeveloper/CompoundObjects

Compound Objects

Lets say there is a PhoneNumber Compound Object.

public class PhoneNumber 
{
    string CountryCode; 
    string AreaCode; 
    string Number;
    string Extension;
}

A Person has two phone numbers:

public class Person 
{
    string Name; 
    ... 
    PhoneNumber Tel; 
    PhoneNumber? Fax;
}

Tel is not nullabe, Fax is nullable.

Accessing Compound Objects

If a compound object property is not nullable then the content of the property is always a valid reference.
If a compound object property is nullable then the content of the property is always a valid reference, but all of the member may be null.
When a compound object property is set the given compound object will be copied.

Person p; 
string number;

number = p.Tel.Number; 
number = p.Fax.Number; // number may be null, Fax is always valid

p.Tel.Number = "12345678"; 
p.Fax.Number = "12345678"; // Fax is always valid

PhoneNumber n;

n = p.Tel; // returns a reference of the compound object 
n.Number = "87654321"; // changes 
p.Tel.Number 
n = p.Fax; // always valid 
n.Number = "87654321"; // changes p.Fax.Number

p.Fax = p.Tel; // creates a copy of p.Tel 
p.Fax.Number = "87654321"; // changes p.Fax.Number but does not change p.Tel.Number

p.Tel = null; // throws a ArgumentNullException 
p.Fax = null; // throws a ArgumentNullException 

n = ctx.CreateStruct<PhoneNumber>(); // creates a new PhoneNumber Struct; 
n.Number = "12345678"; 
p.Tel = n; // creates a copy of n
p.Tel.Number = "18273645"; // changes p.Tel.Number but does not change n.Number 
n.Number = "87654321"; // changes n.Number but does not change p.Tel.Number