クライアント/サーバーへの移行

4D v16

クライアント/サーバーへの移行

ビデオ中で説明されている操作に加え、以下の点にも留意してください:

クライアント/サーバーモードの利用はとてもシンプルです。

トリガーはサーバー上で実行されます。

ユーザーとの対話を期待するようなコマンド (ALERT、DIALOG、CONFIRM、ALERT等) をサーバー上で実行してはいけません。サーバー画面は誰も見ておらず、ダイアログを閉じる人はいないからです。特にサービスとして実行されている場合、ダイアログを表示しないようにしてください。

サーバー上でもプロセスを実行することができます (ストアドプロシージャー)。

Video script

Now we're going to learn about using a database in client/server mode.

Up until now, we've been programming in single-user mode; so let's look at how it works in client/server mode:

Let's quit 4D
We take the same database and start it on the server
The server starts and we see that there are currently 0 users
We start a client machine
We connect to a 4D Server
We choose the database we want from the list of published databases

And we see that in client mode:

We have the same interface and the same contents as before
We can display the technicians, the interventions
And perform all the same operations

Since 4D is multiplatform, the same server can distribute information to both Mac and Windows machines:

Let's switch to Windows
Start 4D.exe
Connect to the same server
And we have the same interface and the same data.

We can modify an intervention on Windows, and we'll immediately see those same modifications on Mac and vice versa.

The server also automatically manages record access conflicts. If we are editing a technician record and we want to open the same record on another client machine:

A message indicates that the record is already in use
And specifies the user, workstation and process concerned.

So much for data in client/server mode.

It just so happens that our development (tables, forms, methods, etc.) is also data: this is the programmer data.

The server also manages the impact of changes made on different machines, as well as the locking of "programmer" records.

Here, the [Intervention] input form is open; if we switch to Windows and finish; it opens the same [Intervention] input form but specifies that another user is currently working on it.

If we hit OK, a lock indicates that the form is currently being used on another machine.

If we close the form on another machine and we go back to Windows, we can unlock the form by clicking on the padlock and then we'll be able to edit it.

The same principle applies to the structure:

We're going to close everything on Mac
Open the structure again
And so we have 2 identical structures
If we take the [Technicians] table and make the relation straight, we can automatically see the change made on Windows in the background.

This means that a team can develop simultaneously since we have access to:

the structure
the methods
the forms
and all the tools available for developers.

Naturally, any changes made in client/server mode can be used again in single-user mode since it's still the same structure and data.

This quick approach lets you see that is quite easy to develop either in a single-user environment or on several machines directly in client-server mode.