Decompose Form logic from BaseAuthBody into a separate model

src/components/auth/BaseAuthBody.jsx

@@ -5,6 +5,7 @@ import React, { Component, PropTypes } from 'react';
 
 import AuthError from 'components/auth/authError/AuthError';
 import { userShape } from 'components/user/User';
+import Form from 'models/Form';
 
 export default class BaseAuthBody extends Component {
     static contextTypes = {
@@ -31,28 +32,14 @@ export default class BaseAuthBody extends Component {
 
     onClearErrors = this.context.clearErrors;
 
-    form = {};
+    form = new Form();
 
-    bindField(name) {
+    bindField = this.form.bindField.bind(this.form);
-        return {
+    serialize = this.form.serialize.bind(this.form);
-            name,
-            ref: (el) => {
-                this.form[name] = el;
-            }
-        };
-    }
 
     autoFocus() {
         const fieldId = this.autoFocusField;
 
-        fieldId && this.form[fieldId] && this.form[fieldId].focus();
+        fieldId && this.form.focus(fieldId);
-    }
-
-    serialize() {
-        return Object.keys(this.form).reduce((acc, key) => {
-            acc[key] = this.form[key].getValue();
-
-            return acc;
-        }, {});
     }
 }

src/models/Form.js

@@ -0,0 +1,38 @@
+export default class Form {
+    fields = {};
+
+    /**
+     * Connects form with React's component
+     *
+     * Usage:
+     * <input {...this.form.bindField('foo')} type="text" />
+     *
+     * @param  {string} name - the name of field
+     *
+     * @return {Object} ref and name props for component
+     */
+    bindField(name) {
+        return {
+            name,
+            ref: (el) => {
+                this.fields[name] = el;
+            }
+        };
+    }
+
+    focus(fieldId) {
+        if (!this.fields[fieldId]) {
+            throw new Error(`The field with an id ${fieldId} does not exists`);
+        }
+
+        this.fields[fieldId].focus();
+    }
+
+    serialize() {
+        return Object.keys(this.fields).reduce((acc, key) => {
+            acc[key] = this.fields[key].getValue();
+
+            return acc;
+        }, {});
+    }
+}