2 files changed, 11 insertions, 1 deletions
diff --git a/src/fields/Document.ts b/src/fields/Document.ts
index 2e873439c..25e239417 100644
--- a/src/fields/Document.ts
+++ b/src/fields/Document.ts
@@ -1,6 +1,6 @@
 import { Key } from "./Key"
 import { KeyStore } from "./KeyStore";
-import { Field, Cast, FieldWaiting, FieldValue, FieldId } from "./Field"
+import { Field, Cast, FieldWaiting, FieldValue, FieldId, Opt } from "./Field"
 import { NumberField } from "./NumberField";
 import { ObservableMap, computed, action } from "mobx";
 import { TextField } from "./TextField";
@@ -128,6 +128,12 @@ export class Document extends Field {
         return false;
     }
 
+    GetTAsync<T extends Field>(key: Key, ctor: { new(): T }, callback: (field: Opt<T>) => void): boolean {
+        return this.GetAsync(key, (field) => {
+            callback(Cast(field, ctor));
+        })
+    }
+
     /**
      * Same as {@link Document#GetAsync}, except a field of the given type
      * will be created if there is no field associated with the given key,
diff --git a/src/fields/KeyStore.ts b/src/fields/KeyStore.ts
index f67257093..f93a68c85 100644
--- a/src/fields/KeyStore.ts
+++ b/src/fields/KeyStore.ts
@@ -27,6 +27,10 @@ export namespace KeyStore {
     export const Caption = new Key("Caption");
     export const ActiveFrame = new Key("ActiveFrame");
     export const DocumentText = new Key("DocumentText");
+    export const LinkedToDocs = new Key("LinkedToDocs");
+    export const LinkedFromDocs = new Key("LinkedFromDocs");
+    export const LinkDescription = new Key("LinkDescription");
+    export const LinkTags = new Key("LinkTag");
     export const Thumbnail = new Key("Thumbnail");
     export const CurPage = new Key("CurPage");
     export const NumPages = new Key("NumPages");