Visual Form Inheritance
lazarus / 6-IDE-CodeTools

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JimBodkins · 2006-11-27 05:00

Mazzias is apparently working on Visual Form Inheritance. (Thanks
Graeme)

I am having a problem with component creation order. (I have created a
few database components. One of which opens the database and must be
created first - and it cant be at the moment apparently). If I
understand this, with Visual Form Inheritance, I should be able to
create a derived form that includes my database component. Which may
solve my problem absent creation ordering. (I created a derived form
type, but found that in the IDE it was too much trouble to use. The
form is an essential part of the newly created project and isnt easily
replaced. It is married to the IDE it appears  ).

Just curious. (I still dont understand why creation order isnt related
to LFM order)

Thanks Jim

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matthijs · 2006-11-27 07:24

When using database components make sure that when compiling you have
all connections closed. Then open the connection when you need it.
This way you circumvent problems with creating.
It is even better to connect to the database when you need it and not
directly at program start. (imo  )

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JimBodkins · 2006-11-27 07:38

I generally agree. In this case, several of the components I made are
data aware. Typical forms contain several dozen of these components.
They are used (Combobox's mainly) to allow the operator to select
appropriate values (obvious). This is a hotel reservation/management
system. This isnt SQL based. It is Unify (I basically did the
interface). If I wait to open the database, then I will have to
manually load each component. I have oncreate event handlers for the
components that load then from the start. The problem is volume. It
isnt one form. For on main application (New reservations) it is about
30 forms. The class that defines the database, consisting of each
table as an object with properties and methods to manipulate the
tables including foreign keys is about 50,000 lines at this point.
That is auto generated directly from the schema - I wrote it in C,
sorry  .

I can handle this, but some of the others are more experts in hotel
management than they are programming. I'm trying to make it as easy
for them as possible.

As a note, openning this database isnt analogous to openning MySQL or
Postgresql really. It just allocates storage at that point basically.
Loading the components is pretty passive also. Its almost stateless.