Prerender executing twice

Question

I have some prerender code that is being used to get information from another list to add into the display of the main list.

I am puzzled - the prerender code executes twice.

 (function () {
 var ctx = {};
 ctx.Templates = {};
 ctx.OnPreRender = preRenderHandler;
 SPClientTemplates.TemplateManager.RegisterTemplateOverrides(ctx);
})();

function preRenderHandler(renderCtx) { 
//        Execute SP Services to get external variables to add into current site
};

the code works fine, just executes twice.

I suspect that this site explains why:

http://geekswithblogs.net/KunaalKapoor/archive/2012/07/18/sharepoint-webpart-life-cycle-events-and-event-sequence.aspx

namely, that there is an OnLoad and Postback event happening resulting in the preRenderhandler running twice?

Is this correct?

What is the best way to stop the code running twice? Is there any benefit in it running twice?

Thanks!

Answer 1

ist absolut logically that the prerender is executed on both onLoad and Postback. Because everytime the control is rendered new, so the prerender is also executed. It would be a Problem if it wouldn´t do so.

Answer 2

The answer I provided to Leopold seemed to be the way to go - set up a variable to detect if the render has executed previously and then stop execution on the second and subsequent passes.

Agreement on this approach provided here:

http://www.codeproject.com/Articles/620110/SharePoint-Client-Side-Rendering-List-Views