fix

lib/Persistent.ts

@@ -1,8 +1,11 @@
 import { Assignable, Serializable } from './interfaces';
 
+type PersistentTypeString = 'string'|'number'|'boolean';
+type PersistentType = string|number|boolean;
+
 export abstract class Persistent implements Assignable, Serializable {
-  private _data: Record<string, unknown> = {};
+  private _data: Record<string, PersistentType> = {};
-  protected readonly properties: Record<string, string> = {};
+  protected readonly properties: Record<string, PersistentTypeString> = {};
 
   public assign (a: Assignable): void {
     this.assign_object (a.to_object ());
@@ -16,11 +19,11 @@ export abstract class Persistent implements Assignable, Serializable {
     for (const key of Object.keys (obj)) {
       const prop = this.properties[key];
       if (typeof prop !== 'undefined' && typeof obj[key] === prop)
-        this._data[key] = obj[key];
+        this._data[key] = obj[key] as PersistentType;
     }
   }
 
-  public to_object (): Record<string, unknown> {
+  public to_object (): Record<string, PersistentType> {
     return this._data;
   }
 
@@ -33,10 +36,10 @@ export abstract class Persistent implements Assignable, Serializable {
   public set (key: string, value: unknown): void {
     const prop = this.properties[key];
     if (typeof prop !== 'undefined' && typeof value === prop)
-      this._data[key] = value;
+      this._data[key] = value as PersistentType;
   }
 
-  public get (key: string): unknown {
+  public get (key: string): PersistentType {
     return this._data[key];
   }
 }