fix: first method in belongsToMany relation

src/index.js

@@ -1,6 +1,7 @@
 
 const Builder = require('./builder');
 const Model = require('./model');
+const Pivot = require('./pivot');
 const Collection = require('./collection');
 const Paginator = require('./paginator');
 const sutando = require('./sutando');
@@ -18,6 +19,7 @@ module.exports = {
   Paginator,
   Collection,
   Model,
+  Pivot,
   Builder,
   Attribute,
   CastsAttributes,

src/model.js

@@ -490,7 +490,7 @@ class Model extends BaseModel {
   }
 
   newPivot(parent, attributes, table, exists, using = null) {
-    return using ? using.constructor.fromRawAttributes(parent, attributes, table, exists)
+    return using ? using.fromRawAttributes(parent, attributes, table, exists)
       : Pivot.fromAttributes(parent, attributes, table, exists);
   }
 

src/relations/belongs-to-many.js

@@ -108,6 +108,20 @@ class BelongsToMany extends compose(
     return new Collection(models);
   }
 
+  async first(columns = ['*']) {
+    const results = await this.take(1).get(columns);
+    return results.count() > 0 ? results.first() : null;
+  }
+
+  async firstOrFail(columns = ['*']) {
+    const model = await this.first(columns);
+    if (model !== null) {
+      return model;
+    }
+
+    throw (new ModelNotFoundError).setModel(this.related.constructor);
+  }
+
   async paginate(page = 1, perPage = 15, columns = ['*']) {
     this.query.select(this.shouldSelect(columns));
 
@@ -116,11 +130,28 @@ class BelongsToMany extends compose(
     });
   }
 
+  async chunk(count, callback) {
+    return await this.prepareQueryBuilder().chunk(count, async (results, page) => {
+      this.hydratePivotRelation(results.all());
+
+      return await callback(results, page);
+    });
+  }
+
+  setUsing(model) {
+    this.using = model;
+    return this;
+  }
+
   as(accessor) {
     this.accessor = accessor;
     return this;
   }
 
+  prepareQueryBuilder() {
+    return this.query.select(this.shouldSelect());
+  }
+
   hydratePivotRelation(models) {
     models.map(model => {
       model.setRelation(this.accessor, this.newExistingPivot(

sutando.mjs

@@ -5,6 +5,7 @@ const {
   Paginator,
   Collection,
   Model,
+  Pivot,
   Builder,
   Attribute,
   CastsAttributes,
@@ -33,6 +34,7 @@ export {
   Paginator,
   Collection,
   Model,
+  Pivot,
   Builder,
   Attribute,
   CastsAttributes,