Adusted the way scan distances are implemented

ref #67

src/models/entities/Scan.ts

@@ -15,7 +15,7 @@ import { Runner } from "./Runner";
 */
 @Entity()
 @TableInheritance({ column: { name: "type", type: "varchar" } })
-export abstract class Scan {
+export class Scan {
   /**
    * Autogenerated unique id (primary key).
    */
@@ -31,14 +31,6 @@ export abstract class Scan {
   @ManyToOne(() => Runner, runner => runner.scans, { nullable: false })
   runner: Runner;
 
-  /**
-   * The scan's distance in meters.
-   * Can be set manually or derived from another object.
-   */
-  @IsInt()
-  @IsPositive()
-  abstract distance: number;
-
   /**
    * Is the scan valid (for fraud reasons).
    * The determination of validity will work differently for every child class.
@@ -48,6 +40,24 @@ export abstract class Scan {
   @IsBoolean()
   valid: boolean = true;
 
+  /**
+   * The scan's distance in meters.
+   * Can be set manually or derived from another object.
+   */
+  @Column({ nullable: true })
+  @IsInt()
+  private _distance?: number;
+
+  /**
+   * The scan's distance in meters.
+   * Can be set manually or derived from another object.
+   */
+  @IsInt()
+  @IsPositive()
+  public get distance(): number {
+    return this._distance;
+  }
+
   /**
    * Turns this entity into it's response class.
    */