73 lines
3.0 KiB
HTML
73 lines
3.0 KiB
HTML
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<html>
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<head>
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<link rel="stylesheet" type="text/css" href="..\styles.css">
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</head>
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<body>
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<img src="..\..\da.png" alt="" align="right">
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<!-------------------------------------------------------------------------->
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<p class="h1">Refresh Update Data Sample</p>
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<p>
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This sample demonstrates how changes made to the data by one of the client applications can be instantly
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propagated to other clients connected to the same server.<br/>
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The following steps are performed to achieve the goal:
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</p>
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<ul>
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<li>
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When the user attempts to edit a record the client application calls the remote method of the server to notify
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that the row is being edited. Row being edited by one client application will be made unavailable for edit by others to
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prevent update conflicts.
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</li>
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<li>
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When the server is informed about a row edit attempt it sends row lock notifications to all clients connected. RO SDK
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<b>callback events</b> are used for this purpose. Also the server maintains the list of locked rows to lock rows on the newly connected clients.
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</li>
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<li>
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When the client finishes editing the row it sends changed data to the server as usual and in addition calls the
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remote method to inform that the row lock is released.
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</li>
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<li>The server notifies all clients about releasing the row lock.</li>
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<li>
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When row release notification is processed by the client it refetches the changed row from the server.
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<b>Dynamic Where</b> is used to fetch particular row.
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</li>
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</ul>
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<p class="h2">Examine the code</p>
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<p>Examine the client:</p>
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<ul>
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<li>Examine <b>TClientForm.btEditClick</b> event handler to see how the record is edited.</li>
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<li>
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See how the client processes row lock notifications, examine <b>TClientForm.OnUpdateAllBlock</b>
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and <b>TClientForm.OnUpdateBlock</b> methods.
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</li>
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<li>See how changed data refresh is performed, examine <b>TClientForm.OnUpdateUnblock</b> method.</li>
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</ul>
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<p>Examine the sample server:</p>
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<ul>
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<li>Examine <b>BlockRow</b> service method to see how the row edit attempt is processed.</li>
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<li>Examine <b>BlockSetOfRows</b> to see how the server interacts with newly connected client.</li>
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<li>Examine <b>UnblockRow</b> service method to see how the row change notification is propagated to connected clients.</li>
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</ul>
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<p class="h2">Getting started</p>
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<ul>
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<li>Run the Sample Server.</li>
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<li>Run two or more instances of the RefreshData sample.</li>
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<li>Load data to every client instance with Load button.</li>
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<li>Click Edit button to edit the row.</li>
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<li>
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See how the row being edited on one client instance is marked 'locked' on others. You may try to edit the locked row,
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the application will forbid doing this.
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</li>
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<li>Make some changes to the row being edited and confirm changes in the edit form.</li>
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<li>See how row locks are relesed on the remaining client instances and how the row is updated.</li>
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<li>
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While the row is being edited on any client launch one more client instance. See how existing row locks are displayed
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on the newly connected client.
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</li>
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</ul>
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</body>
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</html>
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