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Flow

Links to this object

To handle editor navigation and support object links consistency Links to this object (key=backlinks) built-in relation is provided by Middleware. This relation handles a list of objects that have a link to the object the relation is set to.

Every time link from one object to another is created - besides setting Links from this object, new link is saved to the ObjectStore.

ObjectStore provides method SubscribeBacklinksUpdate that generates subscription on every links changes in store.

Special service backlinks.UpdateWatcher was designed to look after changes on links using backlinks subscription. On links change the service triggers StateAppend of target objects, that helps to:

  • inject derived details of target object. Backlinks are retrieved from store on this step
  • generate necessary events to notify dependent objects about details changes

Internal Flags

All objects can have relation InternalFlags set to its details. This relation handles list of flags used mainly by client:

  • DeleteEmpty - stands for deletion of empty objects. Middleware performs object deletion on ObjectClose in case object has this internal flag.
  • SelectType - stands for showing Type Picker on client-side.
  • SelectTemplate - stands for showing Template Picker on client-side.

Client passes internalFlags value on object creation, and then the content of its value could be modified only by Middleware. However, it only deletes flags, and it deletes them on ALL commands where new state of object is applied EXCEPT these cases:

  1. ObjectApplyTemplate
  2. ObjectSetObjectType - deletes only DeleteEmpty and SelectType
  3. ObjectSetDetails - deletes only DeleteEmpty
  4. ObjectOpen
  5. ObjectClose
  6. BlockTextSetText - if no changes in block were made OR it is title or description block

In all other cases Middleware performs state Non-Emptiness check. And if state is not empty, it wipes internalFlags.

Empty state definition used in check

A state that either has no blocks or all blocks have no text inside. This definition is awful, because these kinds of objects would be deleted on closing:

  • Object has no blocks filled, but a lot of details pre-filled by user
  • Object has a lot of custom blocks that could not handle text

TODO:

  1. Redesign state.IsEmpty check. Reasons are mentioned above
  2. Think about moving SelectType and SelectTemplate flags controlling logic to clients, because Middleware does not use these flags, but have very complex logic on its maintaining

Blank template

Blank template is a virtual template for all kinds of objects, that could be chosen as default on client-side. Middleware does not have built-in template object to apply it on state on desired object, but understands literal blank as a value of templateId field of following commands:

  • BlockLinkCreateWithObject
  • ObjectCreate
  • ObjectCreateSet
  • ObjectApplyTemplate

If blank is chosen as templateId in one of first three commands, Middleware acts as no template was chosen at all and creates new object regarding remaining parameters of request.

If blank is chosen as templateId in ObjectApplyTemplate, Middleware creates applies new state, leaving only Type and Layout of previous state.

System Objects Update

Some Object types and Relations are recognized as System ones, because application business logic depends on their content.

Examples of system types are Note, Task and Bookmark. Non-system - Contact, Goal and Feature.

Examples of system relations are Id, Name and Done. Non-system - FocalRatio, Instagram and HowToReproduce.

System types and relations could not be modified by the users or deleted from spaces. However, sometimes developers need to modify system objects to support some new features.

To handle system object update and save backward compatibility each system object type and relation has its own Revision. Anytype will update system objects only if Revision of object from marketplace is higher than Revision of object from user's space.

How to update system objects

  1. Update description of system object, that is stored in pkg/lib/bundle
  2. Increase revision field of system type/relation or put "revision":1 if it was empty
  3. Generate go-level variables for new version of types and relations using pkg/lib/bundle/generator
  4. Make sure that new fields are taken into account in System Object Reviser. (Right now only these fields are checked: Revision, Name, Description, IsHidden, IsReadonly)
  5. Build and run Anytype. All system objects with lower Revision should be updated according your changes in all spaces