Merge pull request #43 from mikeric/dependant-attributes-for-computed-properties

Computed properties

@@ -26,7 +26,7 @@ describe('Rivets.Binding', function() {
     it('subscribes to the model for changes via the adapter', function() {
       spyOn(rivets.config.adapter, 'subscribe');
       binding.bind();
-      expect(rivets.config.adapter.subscribe).toHaveBeenCalled();
+      expect(rivets.config.adapter.subscribe).toHaveBeenCalledWith(model, 'name', binding.set);
     });
 
     describe('with preloadData set to true', function() {
@@ -38,8 +38,8 @@ describe('Rivets.Binding', function() {
         spyOn(binding, 'set');
         spyOn(rivets.config.adapter, 'read');
         binding.bind();
+        expect(rivets.config.adapter.read).toHaveBeenCalledWith(model, 'name');
         expect(binding.set).toHaveBeenCalled();
-        expect(rivets.config.adapter.read).toHaveBeenCalled();
       });
     });
 
@@ -55,6 +55,19 @@ describe('Rivets.Binding', function() {
         expect(binding.set).toHaveBeenCalledWith('espresso');
       });
     });
+
+    describe('with dependencies', function() {
+      beforeEach(function() {
+        binding.options.dependencies = ['fname', 'lname'];
+      });
+
+      it('sets up observers on the dependant attributes', function() {
+        spyOn(rivets.config.adapter, 'subscribe');
+        binding.bind();
+        expect(rivets.config.adapter.subscribe).toHaveBeenCalledWith(model, 'fname', binding.dependencyCallbacks['fname']);
+        expect(rivets.config.adapter.subscribe).toHaveBeenCalledWith(model, 'lname', binding.dependencyCallbacks['lname']);
+      });
+    });
   });
 
   describe('set()', function() {

@@ -63,6 +63,18 @@ class Rivets.Binding
       if Rivets.config.preloadData
         @set Rivets.config.adapter.read @model, @keypath
 
+    if @options.dependencies?.length
+      @dependencyCallbacks = {}
+
+      for keypath in @options.dependencies
+        callback = @dependencyCallbacks[keypath] = (value) =>
+          @set if @options.bypass
+            @model[@keypath]
+          else
+            Rivets.config.adapter.read @model, @keypath
+        
+        Rivets.config.adapter.subscribe @model, keypath, callback
+
     if @type in @bidirectionals
       bindEvent @el, 'change', @publish
 
@@ -75,6 +87,11 @@ class Rivets.Binding
   unbind: =>
     Rivets.config.adapter.unsubscribe @model, @keypath, @set
 
+    if @options.dependencies?.length
+      for keypath in @options.dependencies
+        callback = @dependencyCallbacks[keypath]
+        Rivets.config.adapter.unsubscribe @model, keypath, callback
+
     if @type in @bidirectionals
       @el.removeEventListener 'change', @publish
 
@@ -104,12 +121,16 @@ class Rivets.View
 
           type = attribute.name.replace bindingRegExp, ''
           pipes = (pipe.trim() for pipe in attribute.value.split '|')
-          path = pipes.shift().split(/(\.|:)/)
+          context = (ctx.trim() for ctx in pipes.shift().split '>')
+          path = context.shift().split /(\.|:)/
           options.formatters = pipes
           model = @models[path.shift()]
           options.bypass = path.shift() is ':'
           keypath = path.join()
 
+          if dependencies = context.shift()
+            options.dependencies = dependencies.split /\s+/
+
           if eventRegExp.test type
             type = type.replace eventRegExp, ''
             options.special = "event"