Fixed use of computed field inside template helpers.

Fixes: #12

Author: mitar

lib.coffee

@@ -8,9 +8,35 @@ class ComputedField
     handle = null
     lastValue = null
 
+    # TODO: Provide an option to prevent using view's autorun.
+    #       One can wrap code with Blaze._withCurrentView(null, code) to prevent using view's autorun for now.
     if currentView = Package.blaze?.Blaze?.currentView
-      autorun = (f) ->
-        currentView.autorun f
+      if currentView._isInRender
+        # Inside render we cannot use currentView.autorun directly, so we use our own version of it.
+        # This allows computed fields to be created inside Blaze template helpers, which are called
+        # the first time inside render. While currentView.autorun is disallowed inside render because
+        # autorun would be recreated for reach re-render, this is exactly what computed field does
+        # anyway so it is OK for use to use autorun in this way.
+        autorun = (f) ->
+          templateInstanceFunc = Package.blaze.Blaze.Template._currentTemplateInstanceFunc
+
+          comp = Tracker.autorun (c) ->
+            Package.blaze.Blaze._withCurrentView currentView, ->
+              Package.blaze.Blaze.Template._withTemplateInstanceFunc templateInstanceFunc, ->
+                f.call currentView, c
+
+          stopComputation = ->
+            comp.stop()
+          currentView.onViewDestroyed stopComputation
+          comp.onStop ->
+            currentView.removeViewDestroyedListener stopComputation
+
+          comp
+
+      else
+        autorun = (f) ->
+          currentView.autorun f
+
     else
       autorun = Tracker.autorun
 

tests_client.coffee

@@ -16,6 +16,17 @@ Template.computedFieldTestTemplate.onCreated ->
 
     output.push f()
 
+Template.computedFieldTestTemplate.helpers
+  bar: ->
+    field = new ComputedField =>
+      foo = Template.currentData()?.foo?()
+      if _.isNumber foo
+        foo % 10
+      else
+        ''
+
+    field()
+
 Template.computedFieldTestTemplate.events
   'click .computedFieldTestTemplate': (event) ->
     Template.instance().field()
@@ -35,21 +46,21 @@ class TemplateTestCase extends ClassyTestCase
       Tracker.afterFlush @expect()
   ,
     ->
-      @assertEqual $('.computedFieldTestTemplate').text(), '42'
+      @assertEqual $('.computedFieldTestTemplate').text(), '42|2'
 
       @internal.set 43
       # Field flush happens automatically when using getter.
       @assertEqual @foo(), 43
 
       # There was no global flush yet, so old value is rendered.
-      @assertEqual $('.computedFieldTestTemplate').text(), '42'
+      @assertEqual $('.computedFieldTestTemplate').text(), '42|2'
 
       Tracker.afterFlush @expect()
   ,
     ->
       # But after global flush we want that the new value is rendered, even if we flushed
       # the autorun before the global flush happened (by calling a getter).
-      @assertEqual $('.computedFieldTestTemplate').text(), '43'
+      @assertEqual $('.computedFieldTestTemplate').text(), '43|3'
 
       Blaze.remove @rendered
 
@@ -82,7 +93,7 @@ class TemplateTestCase extends ClassyTestCase
       Tracker.afterFlush @expect()
   ,
     ->
-      @assertEqual $('.computedFieldTestTemplate').text(), '45'
+      @assertEqual $('.computedFieldTestTemplate').text(), '45|5'
 
       # Autorun is running again.
       @assertTrue @foo._isRunning()
@@ -107,7 +118,7 @@ class TemplateTestCase extends ClassyTestCase
       Tracker.afterFlush @expect()
   ,
     ->
-      @assertEqual $('.computedFieldTestTemplate').text(), ''
+      @assertEqual $('.computedFieldTestTemplate').text(), '|'
 
       $('.computedFieldTestTemplate').click()
 
@@ -143,25 +154,25 @@ class TemplateTestCase extends ClassyTestCase
       Tracker.afterFlush @expect()
   ,
     ->
-      @assertEqual $('.computedFieldTestTemplate').text(), '42'
+      @assertEqual $('.computedFieldTestTemplate').text(), '42|2'
 
       @internal.set 43
 
-      @assertEqual $('.computedFieldTestTemplate').text(), '42'
+      @assertEqual $('.computedFieldTestTemplate').text(), '42|2'
 
       Tracker.afterFlush @expect()
   ,
     ->
-      @assertEqual $('.computedFieldTestTemplate').text(), '43'
+      @assertEqual $('.computedFieldTestTemplate').text(), '43|3'
 
       @internal.set 53
 
-      @assertEqual $('.computedFieldTestTemplate').text(), '43'
+      @assertEqual $('.computedFieldTestTemplate').text(), '43|3'
 
       Tracker.afterFlush @expect()
   ,
     ->
-      @assertEqual $('.computedFieldTestTemplate').text(), '53'
+      @assertEqual $('.computedFieldTestTemplate').text(), '53|3'
 
       Blaze.remove @rendered
 

tests_client.html

@@ -1,3 +1,3 @@
 <template name="computedFieldTestTemplate">
-  <div class="computedFieldTestTemplate">{{foo}}</div>
+  <div class="computedFieldTestTemplate">{{foo}}|{{bar}}</div>
 </template>