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POManaging AJAX control loading sequence on a page
 

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    <p>I think I am experiencing race conditions with an AJAX web application. I am using JQuery 1.4.4 to handle the AJAX requests.</p> <p>I have a menu control/class that the user clicks to display controls for manipulating data. Clicking the menu can display multiple controls which initialise independently of each other and load at different speeds and become available in an unpredictable order (the A in AJAX I guess...).</p> <p>The controls interact with each other, for example selecting an item in one control adds it to another. The interaction happens by triggering the event in the source control using JQuery and binding to that event in the destination control. The issue seems to be that when you start interacting with a control before all controls are finished initialising you can cause problems. For example, adding an item appears to have worked in the source control whilst the destination control is still loading but when it has loaded it doesn't show the added item. I think that this is because the add item request is fired and completed whilst the load is still happening which then overwrites any changes.</p> <p>The intention in the design of the controls was to keep them as independent of each other as possible and for them to not call directly into each other's methods and properties if possible. The same controls are used in a variety of contexts and are unaware of what other controls are being displayed at the same time. There is a central class that controls the display and hiding of the controls - the menu.</p> <p>Could anyone suggest an approach that would keep the controls / classes loosely coupled but be able to manage the dependencies between them and to know when it is OK to allow interaction?</p> <p>A few ideas that I have are below. Any thoughts on these or further suggestions are appreciated. </p> <ol> <li><p>The menu class could maintain some kind of flag that indicates when all controls are initialised - this would be based say on an incrementing count that is incremented on the successful load of each control. This is the only class that is aware of the controls that are currently in use but it is done in a generic way where the controls pass themselves in to be shown.</p></li> <li><p>Loaded events are fired by each control and other controls being shown in that context bind to each other's loaded event. The controls would need to know more about the context in which they are being used though so that they know when they were the last control to be loaded and thus the page was ready to be intereacted with.</p></li> <li><p>Implement a queue of requests that get executed once the page is loaded. This seems a little too synchronous though.</p></li> <li><p>Upgrading to JQuery 1.6.2 is on the cards for consideration but not scheduled. I am not sure if deferred would be the correct option here anyway due to the generic / anonymous nature of the controls.</p></li> </ol> <p>Thanks for your help</p>
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