improve persistent class

lib/Persistent.ts

@@ -0,0 +1,46 @@
+import { Assignable, Serializable } from './interfaces';
+
+export abstract class Persistent implements Assignable, Serializable {
+  private _data: Record<string, unknown> = {};
+  private _properties: Record<string, string>;
+
+  public constructor (props: Record<string, string>) {
+    this._properties = props;
+  }
+
+  public assign (a: Assignable): void {
+    this.assign_object (a.to_object ());
+  }
+
+  public assign_to (a: Assignable): void {
+    a.assign (this);
+  }
+
+  public assign_object (obj: Record<string, unknown>): void {
+    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];
+    }
+  }
+
+  public to_object (): Record<string, unknown> {
+    return this._data;
+  }
+
+  public serialize (formatted = false): string {
+    if (formatted)
+      return JSON.stringify (this.to_object ());
+    return JSON.stringify (this.to_object (), null, 2);
+  }
+
+  public set (key: string, value: unknown): void {
+    const prop = this._properties[key];
+    if (typeof prop !== 'undefined' && typeof value === prop)
+      this._data[key] = value;
+  }
+
+  public get (key: string): unknown {
+    return this._data[key];
+  }
+}

lib/interfaces/Assignable.ts

@@ -1,34 +1,5 @@
 export interface Assignable {
   assign (a: Assignable): void;
   assign_to (a: Assignable): void;
-}
-
-export abstract class Persistent {
-  private data: Record<string, unknown> = {};
-  private properties: Record<string, string>;
-
-  public constructor() {
-    this.properties = this.define_properties();
-  }
-
-  public abstract define_properties(): Record<string, string>;
-
-  public assign (da: Assignable): void {
-    this.assign_object (da.get_data ());
-  }
-
-  public assign_to (da: Assignable): void {
-    da.assign (this);
-  }
-
-  public assign_object (obj: Record<string, unknown>): void {
-    for (const key of Object.keys (obj))
-      this.data[key] = obj[key];
-  }
-
-  public get_data (): Record<string, unknown> {
-    return this.data;
-  }
-
-  wip
+  to_object (): Record<string, unknown>;
 }