Sometimes the tiniest little throw-away comment on an article out there somewhere can prove useful to someone. Sometimes, it’s even a comment I’ve made.
That’s Andrew “AC” Clark (@bitterac) who tweeted. I may get a club soda out of it, but at Andrew’s suggestion, I figured I’d put up a post as well.
There’s far less documentation about SharePoint 2013’s REST capabilities than most of us would like. As has happened so many times in the past, the blogosphere fills in the gaps.
The post where Andrew Clark found my comment was a great one by Andrew Connell (@andrewconnell) about Applying Filters to Lookup Fields with the SharePoint 2013 REST API.
Andrew Connell (this post is a bit of an Andrew festival – an AC festival, at that) gave extremely useful (and hard to find) info about how to filter based on the values of lookup columns in SharePoint lists using REST. He covered regular lookup columns as well as Managed Metadata columns.
What it comes down to is using the projection to the source of the lookup or Managed Metadata column and then filtering base on the original, underlying value. We do this in REST for SharePoint using the $expand operator.
My comment was about needing to figure out the projection for an Author (Created By) column. The columns Created By and Modified By are populated by SharePoint automagically and the data used for that population is stored in the User Information List. This is a semi-hidden list which exists in the root of each Site Collection. I say semi-hidden because it’s actually the list you’re looking at when you go into the People and Groups view in Site Settings.
If you need to retrieve the name of the Author in a REST call, you can make it work by adding the projection for the Author column.
Going a little further, you can request any of the data you’re used to seeing on the userdisp.aspx page (_layouts/15/userdisp.aspx?Force=true).
It doesn’t really make a lot of sense when you look at it (at least not to me), but by adding the $expand clause, you can retrieve the corresponding info the the User Information List. It feel like you’d need to specify where that list is or something, but under the covers that happens for you.
It seems that by providing each of the values you want in both the $select and the $expand operators, it works. I couldn’t find any documentation on this anywhere. AC2 (the Connell one) has suggested to me several times that it makes sense to simply look at the OData standard. As he said in a reply to me on the same post:
For me, there’s simply nothing better than the raw SDKs & specs on the www.odata.org site. Aside from that, I’ll query www.StackOverflow.com. Then, as a SharePoint guy, you then need to look at WCF Data Services and see what it does not support in the OData v3 spec & the same is true for SharePoint 2013.
I think this stuff is about as clear as mud, but the main reason is that I haven’t spent a lot of time with it yet. REST calls are just a different flavor of how we ask for data in other languages. It’s simply a matter of getting the accent right.