I’m going to do one more CSR Template that doesn’t really render anything, but rather changes something that SPClientTemplates actually renders, an autocomplete template. This one is a little less invasive, because it also doesn’t override the render method, so it doesn’t have to call the out of box renderer and be aware of the consequences of doing that. It can do that because it only cares about a single field, the one it’s going to modify, so it can safely do it’s work as soon as that field is rendered. That means that it can just override OnPreRender and OnPostRender.
I have two goals in this post. First I want to show using CSR in SharePoint to do something cool (or at least useful), cascading lookups. Second I’d like to show a utility page that allows you to configure JSLink in a much better way than setting the JSLink property on a web part using the browser.
For the first goal, I’m going to create cascading lookup lists in a SharePoint form. I chose cascading lookups for a number of reasons:
- It’s a form customization that people frequently ask how to implement on forums like stack exchange (probably the single most common request).
- There is a nice implementation built into the jquery.SPServices library by Marc Anderson, which I’m going to use.
- It doesn’t require any custom rendering. Everything it does occurs after rendering. But it does have to override the render method, so it will need to pass through the rendering to the out of box client templates using the same technique as CSRSpy from my last post.
So, what can you do with CSR? You can develop display templates to modify list forms, views, and search results. As you might imagine, that’s a pretty big topic, so this post (and several follow up posts) will talk about overriding the rendering of fields in list forms. Eventually, I plan to post about view and search display templates as well.
In this post I’m going to demonstrate a CORS Wrapper for postMessage operations, specifically in SharePoint, and intended to make CORS operations as simple as the Ajax operations we’re more familiar with. I’m going to develop the same simple pages I used in my last post, only using the CORS Wrapper this time. Then I’ll dump the CORS Wrapper on you. I’m not going to talk a great deal about the code, I’ve included a ridiculous number of comments in the code to explain what I’m doing.
And yet, in my experience, a lot of developers think this is too complicated and don’t want to deal with it. I think the reasons for this are twofold:
- SharePoint and it’s web services are already complicated. First, there’s a bunch of them, and they all take different parameters. And you need to set different headers depending on what you’re doing. And is it a GET, or POST, or MERGE. And they’re not very well documented, although that’s getting better. There are plenty of simple examples, but few complex ones (for instance, a lot is left to the imagination when it comes to filters or how lazy loading works).
- While postMessage does not add a ton of complexity, adding any complexity at all makes developers groan in agony (mostly because of reason 1).
Looks like an opportunity for some sort of CORS Wrapper or library. Deal with the complexity once, and forever more use the library to hide most if not all of the additional complexity.