Casts

From RemObjects Software

This is a Oxygene Language Feature topic
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Type Casts

Typecasting allows you to override the type of a class to that of one of its descendants. There are two difference syntaxes available:

<variable> as <type>
<type>(<variable>)

In the first, the type is checked first and an exception is raised if the variable is not the correct type.

In the second syntax, the cast will return nil if the type does not match.

Is

The "is" keyword is used in two contexts:

• type checking
• generic constraints

Type Checking

if <object> is <type> then ...
if <object> is not <type> then ...

Generic Constraints

Within a generics context, 'is' is used within a where clause:

type
  MyArrayList<T> = public class(ArrayList, IPersistentCollection)
    where T is PersistentObject, T has constructor;

As well as allowing you to check for a particular type, Oxygene generics also supports 'is record' and 'is class':

type
  GenericThatOnlyTakesARecord<T> = class
  where T is record;
    FVal: T;
  public
    constructor (Val: T);
  end;

  GenericThatOnlyTakesAClass<T> = class
  where T is class;
    FVal: T;
  public
    constructor (Val: T);
  end;

See Also

• Generics
• Expressions

Product: RemObjects Oxygene (formerly known as Chrome)
Current version: 3.0 Previous Versions: 'Joyride' (2.0), 'Floorshow' (1.5), 'Adrenochrome' (1.0)

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