Can't use helper within

Question

I'm trying to make it so certain buttons will be disabled if the Meteor app loses network connectivity.

For some reason, this code breaks. If I move the {{criticalButton}} elsewhere, like within <p> tags, it works fine. But within the <button>, and I get the error below.

HTML:

<button class="btn btn-primary" {{criticalButton}}>Update</button>

Coffee:

Template.registerHelper 'criticalButton', ->
  return not Meteor.status().connected and 'disabled="disabled"'

Console error:

"Exception from Tracker recompute function: String contains an invalid character
AttributeHandler.prototype.update@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1057:4
ElementAttributesUpdater.prototype.update@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1372:6
.visitTag/updateAttributes@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1477:8
viewAutorun/</<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1821:15
Template._withTemplateInstanceFunc@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:3382:11
viewAutorun/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1820:0
Blaze._withCurrentView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:2105:11
viewAutorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1819:0
Tracker.Computation.prototype._compute@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:308:4
Tracker.Computation@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:224:4
Tracker.autorun@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:499:10
Blaze.View.prototype.autorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1831:13
.visitTag@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1482:10
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:103:0
.visitArray@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1416:6
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:116:0
.visitTag@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1495:30
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:103:0
doMaterialize@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1933:29
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
doRender@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1931:6
viewAutorun/</<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1821:15
Template._withTemplateInstanceFunc@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:3382:11
viewAutorun/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1820:0
Blaze._withCurrentView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:2105:11
viewAutorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1819:0
Tracker.Computation.prototype._compute@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:308:4
Tracker.Computation@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:224:4
Tracker.autorun@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:499:10
Blaze.View.prototype.autorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1831:13
Blaze._materializeView/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1922:0
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
Blaze._materializeView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1921:2
.visitObject@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1513:21
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:118:13
doMaterialize@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1933:29
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
doRender@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1931:6
viewAutorun/</<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1821:15
Template._withTemplateInstanceFunc@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:3382:11
viewAutorun/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1820:0
Blaze._withCurrentView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:2105:11
viewAutorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1819:0
Tracker.Computation.prototype._compute@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:308:4
Tracker.Computation@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:224:4
Tracker.autorun@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:499:10
Blaze.View.prototype.autorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1831:13
Blaze._materializeView/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1922:0
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
Blaze._materializeView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1921:2
.visitObject@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1513:21
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:118:13
doMaterialize@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1933:29
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
doRender@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1931:6
viewAutorun/</<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1821:15
Template._withTemplateInstanceFunc@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:3382:11
viewAutorun/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1820:0
Blaze._withCurrentView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:2105:11
viewAutorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1819:0
Tracker.Computation.prototype._compute@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:308:4
Tracker.Computation@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:224:4
Tracker.autorun@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:499:10
Blaze.View.prototype.autorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1831:13
Blaze._materializeView/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1922:0
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
Blaze._materializeView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1921:2
.visitObject@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1513:21
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:118:13
doMaterialize@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1933:29
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
doRender@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1931:6
viewAutorun/</<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1821:15
Template._withTemplateInstanceFunc@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:3382:11
viewAutorun/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1820:0
Blaze._withCurrentView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:2105:11
viewAutorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1819:0
Tracker.Computation.prototype._compute@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:308:4
Tracker.Computation@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:224:4
Tracker.autorun@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:499:10
Blaze.View.prototype.autorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1831:13
Blaze._materializeView/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1922:0
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
Blaze._materializeView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1921:2
.visitObject@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1513:21
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:118:13
.visitArray@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1416:6
.visit@http://localhost:3000/packages/htmljs.js?567eb96d5d22631c03d6aca6afa4c42f0d1295f2:116:0
doMaterialize@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1933:29
Tracker.nonreactive@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:525:11
doRender@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1931:6
viewAutorun/</<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1821:15
Template._withTemplateInstanceFunc@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:3382:11
viewAutorun/<@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1820:0
Blaze._withCurrentView@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:2105:11
viewAutorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1819:0
Tracker.Computation.prototype._compute@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:308:4
Tracker.Computation@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:224:4
Tracker.autorun@http://localhost:3000/packages/tracker.js?21f0f4306879f57e10ad3a97efe9ea521c5b5775:499:10
Blaze.View.prototype.autorun@http://localhost:3000/packages/blaze.js?4e49999979a58da0e2265f7bd3f5910f9901b07b:1831:13"

score 1 · Accepted Answer · answered Mar 22 '15 at 22:00

1

Try this :

HTML

<button class="btn btn-primary" disabled="{{criticalButton}}">
  Update
</button>

Coffee

Template.registerHelper 'criticalButton', ->
  return not Meteor.status().connected

You can return a boolean value from a Blaze helper to indicate the value of a "boolean" HTML attribute like disabled, checked, required, etc...

answered Mar 22 '15 at 22:00

saimeunt

22,666
2
56
61

This may be out of spec: http://stackoverflow.com/questions/6961526/correct-value-for-disabled-attribute – Michael Cole Jul 28 '16 at 02:20

Can't use helper within element?

1 Answers1

Can't use helper within