How to implement multiple inheritance in delphi?
Solution 1:
Delphi does not support Multiple Inheritance. But classes can support / implement multiple interfaces and you can delegate interface implementation, so you can kinda simulate multiple inheritence.
Solution 2:
Use interfaces. Something like this (Off the top of my head, based on your description.....)
type
IBikeWheel = interface
...
end;
IXYZ = interface
...
end;
IFrontWheel = interface(IBikeWheel)
...
end;
TBike = class
...
end;
TBikeWheel = class(TObject, IBikeWheel);
TBikeWheelXYZ = class(TBikeWheel, IXYZ);
TBikeFrontWheelXYZ = class(TBikeWheelXYZ, IFrontWheel);
Then implement classes for the interfaces that do what the corresponding classes in your old (presumably C/C++) library does and instantiate them in the corresponding class's constructor.
Solution 3:
Use polymorhism to implment each 'thing' as an object hierarchy in its own right and then add object properties to that object in turn. So, create a hierarchy of wheels, and a hierarchy of bikes. Then add wheels to bikes as fields in the ancestor bike object. See below.
TBikeWheel = class
TBikeWheelXYZ = class( TBikeWheel )
TBike = class
FFrontWheel : TBikeWheel;
property FrontWheel : TBikeWheel
read FrontWhell
TBikeABC = class( TBike)
constructor Create;
end;
constructor TBikeABC.Create;
begin
inherited;
FFrontWheel := TBikeWheel.Create;
end;
TBikeXYZ = class( TBike)
constructor Create;
end;
constructor TBikeXYZ.Create;
begin
inherited;
FFrontWheel := TBikeWheelXYZ.Create;
end;