json_directive.coffee

app = angular.module 'hoge'

app.directive 'json', ->
  {
    require: 'ngModel'
    link: (scope, elm, attr, ctrl) ->
      ctrl.$parsers.push (value) ->
        try
          parsed = angular.fromJson(value)
          isValid = true
        catch error
          isValid = false
        ctrl.$setValidity('json', isValid)
        return if isValid then parsed else undefined

      ctrl.$formatters.push (value) ->
        try
          dumped = angular.toJson(value)
          isValid = true
        catch error
          isValid = false
        ctrl.$setValidity('json', isValid)
        return if isValid then dumped else undefined
  }