Close #78, accessors for JoinQueryBuilder

package.json

@@ -1,6 +1,6 @@
 {
   "name": "safe-typeorm",
-  "version": "1.0.16",
+  "version": "1.0.17",
   "description": "Make TypeORM much safer",
   "main": "lib/index.js",
   "typings": "lib/index.d.ts",

src/builders/JoinQueryBuilder.ts

@@ -1,4 +1,5 @@
 import { DomainError } from "tstl/exception/DomainError";
+import { OutOfRange } from "tstl/exception/OutOfRange";
 import * as orm from "typeorm";
 
 import { Belongs } from "../decorators/Belongs";
@@ -128,6 +129,34 @@ export class JoinQueryBuilder<Mine extends object> {
         return builder;
     }
 
+    /* -----------------------------------------------------------
+        ACCESSORS
+    ----------------------------------------------------------- */
+    public has(
+        field: SpecialFields<Mine, Relationship.Joinable<any>>,
+    ): boolean {
+        return this.joined_.has(field);
+    }
+
+    public get<Field extends SpecialFields<Mine, Relationship.Joinable<any>>>(
+        field: SpecialFields<Mine, Relationship.Joinable<any>>,
+    ): JoinQueryBuilder<Relationship.Joinable.TargetType<Mine, Field>> {
+        const found: IJoined | undefined = this.joined_.get(field);
+        if (found === undefined)
+            throw new OutOfRange(
+                `Error on safe.JoinQueryBuilder.get(): unable to find the matched key - "${field}".`,
+            );
+        return found.builder;
+    }
+
+    public size(): number {
+        return this.joined_.size;
+    }
+
+    public empty(): boolean {
+        return this.size() === 0;
+    }
+
     /* -----------------------------------------------------------
         RAW JOIN
     ----------------------------------------------------------- */