ModelRelation: add count(), has() methods

src/db/ModelRelation.ts

@@ -53,6 +53,18 @@ export default abstract class ModelRelation<S extends Model, O extends Model, R
     public abstract async eagerLoad(relations: ModelRelation<S, O, R>[]): Promise<ModelQueryResult<O>>;
 
     public abstract async populate(models: ModelQueryResult<O>): Promise<void>;
+
+    public async count(): Promise<number> {
+        const models = await this.get();
+        if (Array.isArray(models)) return models.length;
+        else return models !== null ? 1 : 0;
+    }
+
+    public async has(model: O): Promise<boolean> {
+        const models = await this.get();
+        if (Array.isArray(models)) return models.find(m => m.equals(model)) !== undefined;
+        else return models && models.equals(model);
+    }
 }
 
 export class OneModelRelation<S extends Model, O extends Model> extends ModelRelation<S, O, O | null> {
@@ -154,7 +166,6 @@ export class ManyModelRelation<S extends Model, O extends Model> extends ModelRe
     public async populate(models: ModelQueryResult<O>): Promise<void> {
         this.cachedModels = models.filter(m => m[this.dbProperties.foreignKey] === this.getModelID());
     }
-
 }
 
 export class ManyThroughModelRelation<S extends Model, O extends Model> extends ModelRelation<S, O, O[]> {
@@ -212,10 +223,8 @@ export class ManyThroughModelRelation<S extends Model, O extends Model> extends
             .map(p => p[`pivot.${this.dbProperties.foreignPivotKey}`]);
         this.cachedModels = models.filter(m => ids.indexOf(m[this.dbProperties.foreignKey]) >= 0);
     }
-
 }
 
-
 export type QueryModifier<M extends Model> = (query: ModelQuery<M>) => ModelQuery<M>;
 
 export type ModelFilter<O extends Model> = (model: O) => boolean | Promise<boolean>;