3 files changed, 65 insertions, 2 deletions

diff --git a/src/new_fields/InkField.ts b/src/new_fields/InkField.ts
index 86a8bd18a..a3157857f 100644
--- a/src/new_fields/InkField.ts
+++ b/src/new_fields/InkField.ts
@@ -39,6 +39,6 @@ export class InkField extends ObjectField {
     }
 
     [Copy]() {
-        return new InkField(deepCopy(this.inkData))
+        return new InkField(deepCopy(this.inkData));
     }
 }
diff --git a/src/new_fields/ObjectField.ts b/src/new_fields/ObjectField.ts
index 0f3777af6..715c6a924 100644
--- a/src/new_fields/ObjectField.ts
+++ b/src/new_fields/ObjectField.ts
@@ -5,7 +5,7 @@ export const Parent = Symbol("Parent");
 export const Copy = Symbol("Copy");
 
 export abstract class ObjectField {
-    protected [OnUpdate]?: (diff?: any) => void;
+    protected [OnUpdate](diff?: any) { };
     private [Parent]?: Doc;
     abstract [Copy](): ObjectField;
 }
diff --git a/src/new_fields/TupleField.ts b/src/new_fields/TupleField.ts
new file mode 100644
index 000000000..1ff57fefc
--- /dev/null
+++ b/src/new_fields/TupleField.ts
@@ -0,0 +1,63 @@
+import { ObjectField, Copy } from "./ObjectField";
+import { IObservableArray, IArrayChange, IArraySplice, observe, Lambda, observable } from "mobx";
+import { UndoManager } from "../client/util/UndoManager";
+import { Field } from "./Doc";
+import { Deserializable } from "../client/util/SerializationHelper";
+import { serializable, createSimpleSchema, list, object } from "serializr";
+import { array } from "prop-types";
+
+const tupleSchema = createSimpleSchema({
+
+});
+
+@Deserializable("tuple")
+export class TupleField<T, U> extends ObjectField {
+
+
+    @serializable(list(object(tupleSchema)))
+    private Data: [T, U];
+
+    public get data() {
+        return this.Data;
+    }
+
+    constructor(data: [T, U]) {
+        super();
+        this.Data = data;
+        this.observeTuple();
+    }
+
+    private observeDisposer: Lambda | undefined;
+    private observeTuple(): void {
+        this.observeDisposer = observe(this.Data as (T | U)[] as IObservableArray<T | U>, (change: IArrayChange<T | U> | IArraySplice<T | U>) => {
+            if (change.type === "update") {
+                UndoManager.AddEvent({
+                    undo: () => this.Data[change.index] = change.oldValue,
+                    redo: () => this.Data[change.index] = change.newValue
+                });
+            } else {
+                throw new Error("Why are you messing with the length of a tuple, huh?");
+            }
+        });
+    }
+
+    protected setData(value: [T, U]) {
+        if (this.observeDisposer) {
+            this.observeDisposer();
+        }
+        this.Data = observable(value) as (T | U)[] as [T, U];
+        this.observeTuple();
+    }
+
+    UpdateFromServer(values: [T, U]) {
+        this.setData(values);
+    }
+
+    ToScriptString(): string {
+        return `new TupleField([${this.Data[0], this.Data[1]}])`;
+    }
+
+    [Copy]() {
+        return new TupleField<T, U>(this.Data);
+    }
+}
\ No newline at end of file