add ability to pass failureCallback to ifValid helper method

- adjust `ifValid` helper method to be able to accept `failureCallback`
as second argument which is executed if form has validation errors
- update README

Author: akuzko

README.md

@@ -124,8 +124,9 @@ for the Form to be able to use validations.
   additional iteration that passes `null` and length of items to `iteratee`
 - `getValidationErrors()` - returns validation errors.
 - `performValidation()` - runs validation routines and sets errors.
-- `ifValid(callback)` - runs validation routines, sets errors, and executes
-  `callback` if there were no errors.
+- `ifValid(successCallback, failureCallback)` - runs validation routines, sets errors,
+  and executes `successCallback` if there were no errors. Otherwise, executes
+  `failureCallback`, if is was passed, **or** `props.onValidationFailed`
 - `getErrors()` - returns an errors object.
 - `getError(name)` - returns an error for an input with a given `name`.
 - `setErrors(errors)` - sets `errors` (object) as form's errors.

src/Form.jsx

@@ -144,19 +144,20 @@ export default class Form extends (PureComponent || Component) {
     return typeof validationz === 'function' ? validationz.call(this) : validationz;
   }
 
-  ifValid(callback) {
+  ifValid(successCallback, failureCallback) {
     const { onValidationFailed } = this.props;
     const errors = this.getValidationErrors();
+    failureCallback = failureCallback || onValidationFailed;
 
     this.setErrors(errors, function() {
       const valid = Object.getOwnPropertyNames(errors).length === 0;
 
-      if (valid && callback) {
-        callback();
+      if (valid && successCallback) {
+        successCallback();
       }
 
-      if (!valid && onValidationFailed) {
-        onValidationFailed(errors, this);
+      if (!valid && failureCallback) {
+        failureCallback(errors, this);
       }
     });
 

test/Form.test.js

@@ -571,6 +571,14 @@ describe('<Form />', function() {
           this.test.wrapper.instance().ifValid(spy);
           expect(spy).toNotHaveBeenCalled();
         });
+
+        it('triggers failure callback if it was passed', function() {
+          const successSpy = createSpy();
+          const failureSpy = createSpy();
+          this.test.wrapper.instance().ifValid(successSpy, failureSpy);
+          expect(successSpy).toNotHaveBeenCalled();
+          expect(failureSpy).toHaveBeenCalled();
+        });
       });
     });