Added belongsTo relation for Lucid models

src/Orm/Proxy/Model/index.js

@@ -219,12 +219,36 @@ class Model {
     this._database = database
   }
 
+  /**
+   * @function query
+   * @description query chain that can be executed on relationship
+   * definations
+   * @param  {Function} callback
+   * @return {Object}
+   */
+  query (callback) {
+    this.constructor._activeRelation.query = callback
+    return this
+  }
+
+
+  /**
+   * @function withPivot
+   * @description method to define columns to be selected on pivot 
+   * table with many to many relations
+   * @return {Object}
+   */
+  withPivot () {
+    this.constructor._activeRelation.withPivot = arguments
+    return this
+  }
+
   /**
    * returns defination for hasOne relation
-   * @param  {String}  binding           [description]
-   * @param  {String}  primaryId         [description]
-   * @param  {String}  relationPrimaryId [description]
-   * @return {Object}                   [description]
+   * @param  {String}  binding
+   * @param  {String}  primaryId
+   * @param  {String}  relationPrimaryId
+   * @return {Object}
    */
   hasOne(binding, targetPrimaryKey, relationPrimaryKey){
 
@@ -254,27 +278,49 @@ class Model {
   }
 
 
-  query (callback) {
-
-    this.constructor._activeRelation.query = callback
-    return this
+  /**
+   * @function belongsTo
+   * @description belongsTo defines one to one relation from relation
+   * model to host model.
+   * @method belongsTo
+   * @param  {String}  binding
+   * @param  {String}  targetPrimaryKey
+   * @param  {String}  relationPrimaryKey
+   * @return {Object}
+   */
+  belongsTo(binding, targetPrimaryKey, relationPrimaryKey) {
 
-  }
+    /**
+     * grabs model from Ioc container
+     * @type {Object}
+    */
+    const model  = Ioc.use(binding)
 
+    /**
+     * relationship primary key to be used on relation model
+     * @type {String}
+     */
+    relationPrimaryKey = relationPrimaryKey || model.primaryKey
 
-  withPivot () {
+    /**
+     * primary id for the target model, the one
+     * who has defined relationship
+     * @type {String}
+     */
+    targetPrimaryKey = targetPrimaryKey || staticHelpers.getRelationKey(model,true)
 
-    this.constructor._activeRelation.withPivot = arguments
+    this.constructor._activeRelation = {model, targetPrimaryKey, relationPrimaryKey, relation:'belongsTo'}
     return this
 
   }
 
+
   /**
    * returns defination for hasMany relation
-   * @param  {String}  binding           [description]
-   * @param  {String}  primaryId         [description]
-   * @param  {String}  relationPrimaryId [description]
-   * @return {Object}                   [description]
+   * @param  {String}  binding
+   * @param  {String}  primaryId
+   * @param  {String}  relationPrimaryId
+   * @return {Object}
    */
   hasMany(binding, targetPrimaryKey, relationPrimaryKey){
 

src/Orm/Proxy/Static/helpers.js

@@ -378,6 +378,18 @@ helpers.hasMany = function (values, model) {
   return helpers.hasOne(values, model, 'noLimit')
 }
 
+/**
+ * belongsTo method for model relation , it is similar to hasOne
+ * but with opposite keys
+ * @method belongsTo
+ * @param  {Object}  values
+ * @param  {Object}  model
+ * @return {Object}
+ */
+helpers.belongsTo = function (values, model) {
+  return helpers.hasOne(values, model)
+}
+
 /**
  * @function belongsToMany
  * @description returns transformed values for belongs to 

test/unit/model-relations.spec.js

@@ -147,6 +147,71 @@ describe('Model Relations', function () {
     .catch(done)
   })
 
+
+  it('should be able to define belongsTo relationship using belongsTo method', function(done) {
+
+    /**
+     * Phone model binded to Ioc container
+     * under App/Model/Phone namespace
+     */
+    class Phone extends Model{
+      user(){
+        return this.belongsTo('App/Model/User')
+      }
+    }
+    Phone.database = db; Phone = Phone.extend()
+
+
+    class User extends Model{
+    }
+    User.database = db; User = User.extend()
+    Ioc.bind('App/Model/User', function() {
+      return User
+    })
+
+    Phone
+    .with(['user'])
+    .then(function(phone){
+      expect(phone.first().user).to.be.an('object')
+      expect(phone.first().user).to.have.property('id')
+      done()
+    })
+    .catch(done)
+  })
+
+
+  it('should be able to fetch belongsTo relationship values for a single result', function(done) {
+
+    /**
+     * Phone model binded to Ioc container
+     * under App/Model/Phone namespace
+     */
+    class Phone extends Model{
+      user(){
+        return this.belongsTo('App/Model/User')
+      }
+    }
+    Phone.database = db; Phone = Phone.extend()
+
+
+    class User extends Model{
+    }
+    User.database = db; User = User.extend()
+    Ioc.bind('App/Model/User', function() {
+      return User
+    })
+
+    Phone
+    .first()
+    .with(['user'])
+    .then(function(phone){
+      expect(phone.toJSON().user).to.be.an('object')
+      expect(phone.toJSON().user).to.have.property('id')
+      done()
+    })
+    .catch(done)
+  })
+
   it('should be able to define hasMany relationship', function(done) {
 
     /**