Allow pre-validating against itself or another set of attributes

README.md

@@ -253,6 +253,8 @@ var isValid = model.isValid(['name', 'age']);
 
 Sometimes it can be useful to check (for instance on each key press) if the input is valid - without changing the model - to perform some sort of live validation. You can execute the set of validators for an attribute, or a hash of attributes, by calling the `preValidate` method and pass it the name of the attribute and the value to validate, or a hash of attributes.
 
+Optionally, it's possible to pass in a hash of attributes that will be used when comparing values, for example - in the `equalsTo` validator. This allows you to preValidate attributes against another set of attributes instead of your model's current attributes.
+
 If the value is not valid, the error message is returned (truthy), otherwise it returns a falsy value.
 
 ```js
@@ -266,7 +268,13 @@ var errorMessage = model.preValidate('attributeName', 'Value');
 //   name: 'Name is required',
 //   email: 'Email must be a valid email'
 // }
-var errors = model.preValidate({name: 'value', email: '[email protected]');
+var errors = model.preValidate({ name: 'value', email: '[email protected]' });
+
+// Validate a hash of attributes against itself
+// Pass in either `true` or an attribute hash as the 2nd parameter.
+// Neither of the examples below will result in any errors.
+var errors = model.preValidate({ password: 'value', passwordConfirmation: 'value' }, true);
+var errors = model.preValidate({ password: 'value' }, { passwordConfirmation: 'value' });
 ```
 
 ## Configuration

src/backbone-validation.js

@@ -176,15 +176,21 @@ Backbone.Validation = (function(_){
       return {
 
         // Check whether or not a value, or a hash of values
-        // passes validation without updating the model
-        preValidate: function(attr, value) {
+        // passes validation without updating the model.
+        // Optional 3rd param lets user pass in a hash of attributes
+        // to pass to validateAttr as the computed attributes
+        preValidate: function(attr, value, atts) {
           var self = this,
               result = {},
               error;
 
           if(_.isObject(attr)){
+            // If value is an object hash, use it as the atts object.
+            // If value is boolean = true, simply use attr object as the atts object.
+            atts = _.isObject(value) ? value : value === true ? attr : undefined;
+
             _.each(attr, function(value, key) {
-              error = self.preValidate(key, value);
+              error = self.preValidate(key, value, atts);
               if(error){
                 result[key] = error;
               }
@@ -193,7 +199,7 @@ Backbone.Validation = (function(_){
             return _.isEmpty(result) ? undefined : result;
           }
           else {
-            return validateAttr(this, attr, value, _.extend({}, this.attributes));
+            return validateAttr(this, attr, value, atts || _.extend({}, this.attributes));
           }
         },
 

tests/preValidate.js

@@ -23,6 +23,9 @@ buster.testCase("preValidate", {
           },
           authenticated: {
             required: false
+          },
+          passwordConfirmation: {
+            equalsTo: 'password'
           }
         }
       });
@@ -64,6 +67,28 @@ buster.testCase("preValidate", {
       "returns nothing when value is valid": function() {
         refute(this.model.preValidate({name: 'name'}));
       }
+    },
+
+    "and pre-validating hash of attributes against itself (2nd param is `true`)": {
+      "returns error object when value is not valid": function() {
+        var result = this.model.preValidate({password: 'password', passwordConfirmation: 'passWORT'}, true);
+        assert(result.passwordConfirmation);
+      },
+
+      "returns nothing when value is valid": function() {
+        refute(this.model.preValidate({password: 'password', passwordConfirmation: 'password'}, true));
+      }
+    },
+
+    "and pre-validating hash of attributes against another hash of attributes (2nd param is a hash)": {
+      "returns error object when value is not valid": function() {
+        var result = this.model.preValidate({passwordConfirmation: 'passWORT'}, {password: 'password'});
+        assert(result.passwordConfirmation);
+      },
+
+      "returns nothing when value is valid": function() {
+        refute(this.model.preValidate({passwordConfirmation: 'password'}, {password: 'password'});
+      }
     }
   }
 });