++version changing transform sig

README.md

@@ -117,9 +117,16 @@ Returns number of subscribers on an exact path. Doesn't count longer or shorter
 
 ### Transform
 
-* `state.transform(key, transformFunction, varargs...)` - returns the new value that was set
+* `state.transform(key).with(transformFunction).using(varargs...)`
 
-The transform function is called with `state.get(key)` followed by the varargs.
+`state.trasnform` returns an object you can call `with` and `using` on in either order. The transformation is only completed
+after both are called.
+
+The transform function is called with stat.get(key) and the varargs:
+
+```javascript
+state.transform('user').with(function(user, favoriteColor, favoriteDrink) { ... }).using('green', 'White Russian');
+```
 
 Calling transform is equivalent to:
 
@@ -168,6 +175,8 @@ There are many ways to incorporate app state into an app. You will probably have
 
 ## Release Notes
 
+- 2.0.0
+    - **Incompatability**: Changed signature of `transform`
 - 1.0.0
     - Can subscribe to multiple keys with one callback
     - Subscribe callbacks are called with the values of keys subscribed

index.js

@@ -1,7 +1,8 @@
 'use strict';
 
 var _       = require('lodash'),
-    Model   = require('model-object');
+    Model   = require('model-object'),
+    Transformer = require('./transformer');
 
 module.exports = {
     init : init
@@ -221,7 +222,11 @@ function set(setting, instance, // This variable is bound
  * @param callback
  * @param {...}
  */
-function transform(key, callback) {
+function transform(key) {
+    return new Transformer(key, this);
+}
+
+function transformr(key, callback) {
     var varargs = [].splice.call(arguments, 2),
         result;
 
@@ -232,6 +237,8 @@ function transform(key, callback) {
     return result;
 }
 
+
+
 function notifySubscribers(changedPath, setting, instance) {
 
     var self = this,

package.json

@@ -1,6 +1,6 @@
 {
   "name": "app-state",
-  "version": "1.1.1",
+  "version": "2.0.0",
   "description": "",
   "main": "index.js",
   "scripts": {

test/indexTest.js

@@ -110,7 +110,7 @@ describe('app state', function() {
         it('should be able to change a key', function() {
             var state = appState.init();
 
-            state.transform('user.profile.library', libraryTransform, [ 'Tom Sawyer', 'Monte Cristo' ]);
+            state.transform('user.profile.library').with(libraryTransform).using([ 'Tom Sawyer', 'Monte Cristo' ]);
 
             state('').should.deep.equal({
                 user : {
@@ -131,6 +131,28 @@ describe('app state', function() {
                 return library;
             }
         });
+        it('should be able to use varargs with using', function() {
+            var state = appState.init();
+
+            state('user', {
+                name : 'dude'
+            });
+
+            state.transform('user').with(function(user, color, drink) {
+                user.favoriteColor = color;
+                user.favoriteDrink = drink;
+                return user;
+            }).using('green', 'White Russian');
+
+            state('').should.deep
+                .equal({
+                    user : {
+                        name : 'dude',
+                        favoriteColor : 'green',
+                        favoriteDrink : 'White Russian'
+                    }
+                });
+        });
     });
     describe('get', function() {
         it('can get root', function() {

transformer/index.js

@@ -0,0 +1,39 @@
+'use strict';
+
+Transformer.prototype.with = transformWith;
+Transformer.prototype.using = using;
+Transformer.prototype.complete = complete;
+Transformer.prototype.transform = transform;
+
+module.exports = Transformer;
+
+function Transformer(key, state) {
+    this.state = state;
+    this.key = key;
+}
+
+function transformWith(transformer) {
+    this.transformer = transformer;
+    if (this.complete()) {
+        this.transform();
+    }
+    return this;
+}
+
+function using() {
+    this.varargs = [].slice.call(arguments);
+    this.varargs.unshift(this.state.get(this.key));
+    if (this.complete()) {
+        this.transform();
+    }
+    return this;
+}
+
+function transform() {
+    var result = this.transformer.apply(null, this.varargs);
+    this.state.set(this.key, result);
+}
+
+function complete() {
+    return !!this.transformer && !!this.varargs;
+}