I am reading a lot about apps, and I dont see the advantage if apps cant talk to each other. In the normal sp 2010 farm solutions you create content types, lists definitions etc, and then you can create list instances that uses those definitions in any web or subweb.

Sometimes I have seen requirements when an item is added in one list, something else needs to be calculated in another list.

With Apps, is that possible?(if the lists are in separate apps) I guess the app should have Site Collection permission which is way too much permission, no?


No they can not "talk" to other apps. Every app instance lives in a seperate app web and does not have access to any other app webs.

Multiple instances of the same app though, can share data if they are deployed from the Central Administration to multiple webs, but that means that all the instances shares the same lists and other SharePoint artifacts.

Navigate to YOURCENTRALADMINADDRESS/_admin/ManageCorporateCatalog.aspx, upload the app from here and then click the triple dots (...) and Deploy

EDIT: This is for SharePoint hosted apps. If you have a Cloud Hosted app it is up to you to handle Multi Tenancy, ergo you could make different instances of an app, or different app share some underlying data storage.

  • with this info, then I guess best practice would be to deploy content types and lists to the host web, and then leave the "business logic" in apps using rest calls to the host web as COB explains on his articles. Apr 25 '13 at 11:43
  • Well that is one approach, but that would mean that the app would be dependent on certain artifacts in the host web. This is a bad practice, and really is not how you should use apps. If you have logic that will need artifacts in the host web you should probably use another technique than apps. Apr 25 '13 at 11:46
  • is this documented somewhere that its a bad practice? Apr 25 '13 at 11:48
  • I can not find a good source right now, but since the apps are ment to be self contained and should be possible to add to any SharePoint solution (think of the marketplace) it would be very bad if the app were dependent on the existance of for example a specific custom list och content type on the host web. Compare it with apps for cellphones, it's the same deal, they should not require the presence of another app on the phone to function. Apr 25 '13 at 11:53
  • You can also refer to msdn.microsoft.com/en-us/library/jj819804.aspx listing all "allowed" dependencies for apps, as you can see it is mostly different service applications listed Apr 25 '13 at 11:55

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