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<a name="Distributed-Object"></a>
<div class="header">
<p>
Next: <a href="Transmitting-Dynamic-Structure.html#Transmitting-Dynamic-Structure" accesskey="n" rel="next">Transmitting Dynamic Structure</a>, Previous: <a href="Overview-of-Pragma-Remote_005fTypes.html#Overview-of-Pragma-Remote_005fTypes" accesskey="p" rel="prev">Overview of Pragma Remote_Types</a>, Up: <a href="Pragma-Remote_005fTypes.html#Pragma-Remote_005fTypes" accesskey="u" rel="up">Pragma Remote_Types</a> [<a href="About-This-Guide.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Distributed-Object-1"></a>
<h4 class="subsubsection">8.1.5.2 Distributed Object</h4>
<p>If we want to implement the notification feature proposed in the
previous section, we have to derive Term_Type. Such a derivation is
possible in a remote types unit like NewTerminal (see below). Any object
of type New_Term_Type becomes a distributed object and any reference to
such an object becomes a fat pointer or a reference to a distributed
object (see Term_Access declaration in <a href="Remote-Access-to-Class-Wide-Types-_0028RACW_0029.html#Remote-Access-to-Class-Wide-Types-_0028RACW_0029">Remote Access to Class Wide Types (RACW)</a>).
</p>
<div class="smallexample">
<pre class="smallexample">
<b>with</b> Types, Terminal; <b>use</b> Types, Terminal;
<b>package</b> NewTerminal <b>is</b>
<b>pragma</b> Remote_Types;
<b>type</b> New_Term_Type <b>is</b>
<b>new</b> Term_Type <b>with</b> <b>null</b> <b>record</b>;
<b>procedure</b> Notify
(MyTerm : <b>access</b> New_Term_Type;
Payer : <b>in</b> Customer_Type;
Amount : <b>in</b> Integer);
<b>function</b> Current <b>return</b> Term_Access;
<b>end</b> NewTerminal;
</pre></div>
<p>In the code below, a client registers his name and his terminal with
RACWBank. Therefore, when any payer transfers some money to him,
RACWBank is able to notify the client of the transfer of funds.
</p>
<div class="smallexample">
<pre class="smallexample">
<b>with</b> NewTerminal, RACWBank, Types; <b>use</b> NewTerminal, RACWBank, Types;
<b>procedure</b> Term1Client <b>is</b>
MyTerm : Term_Access := Current;
Customer : Customer_Type := "poor";
Password : Password_Type := "yyyy";
<b>begin</b>
Register (MyTerm, Customer, Password);
-- [...] Execute other things
<b>end</b> Term1Client;
</pre></div>
<p>In the code below, a second client, the payer, registers his terminal
to the bank and executes a transfer to the first client.
</p>
<div class="smallexample">
<pre class="smallexample">
<b>with</b> NewTerminal, RACWBank, Types; <b>use</b> NewTerminal, RACWBank, Types;
<b>procedure</b> Term2Client <b>is</b>
MyTerm : Term_Access := Current;
Payer : Customer_Type := "rich";
Password : Password_Type := "xxxx";
Payee : Customer_Type := "poor";
<b>begin</b>
Register (MyTerm, Payer, Password);
Transfer (Payer, Password, 100, Payee);
<b>end</b> Term2Client;
</pre></div>
<p>In the code below, we describe the general design of Transfer. Classical
operations of Withdraw and Deposit are performed. Then, RACWBank
retrieves the terminal of the payee (if present) and invokes a
dispatching operation by dereferencing a distributed object Term. The
reference is examined at run-time, and the execution of this operation
takes place on the partition on which the distributed object resides.
</p>
<div class="smallexample">
<pre class="smallexample">
<b>with</b> Types; <b>use</b> Types;
<b>package</b> <b>body</b> RACWBank <b>is</b>
<b>procedure</b> Register
(MyTerm : <b>in</b> Term_Access;
Customer : <b>in</b> Customer_Type;
Password : <b>in</b> Password_Type) <b>is</b>
<b>begin</b>
Insert_In_Local_Table (MyTerm, Customer);
<b>end</b> Register;
<b>procedure</b> Transfer
(Payer : <b>in</b> Customer_Type;
Password : <b>in</b> Password_Type;
Amount : <b>in</b> Positive;
Payee : <b>in</b> Customer_Type)
<b>is</b>
-- Find Customer terminal.
Term : Term_Access
:= Find_In_Local_Table (Payee);
<b>begin</b>
Withdraw (Payer, Amount);
Deposit (Payee, Amount);
<b>if</b> Term /= <b>null</b> <b>then</b>
-- Notify on Payee terminal.
Notify (Term, Payer, Amount);
<b>end</b> <b>if</b>;
<b>end</b> Transfer;
-- [...] Other services
<b>end</b> RACWBank;
</pre></div>
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Next: <a href="Transmitting-Dynamic-Structure.html#Transmitting-Dynamic-Structure" accesskey="n" rel="next">Transmitting Dynamic Structure</a>, Previous: <a href="Overview-of-Pragma-Remote_005fTypes.html#Overview-of-Pragma-Remote_005fTypes" accesskey="p" rel="prev">Overview of Pragma Remote_Types</a>, Up: <a href="Pragma-Remote_005fTypes.html#Pragma-Remote_005fTypes" accesskey="u" rel="up">Pragma Remote_Types</a> [<a href="About-This-Guide.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
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