Class: Volt::IfBinding

Inherits:
BaseBinding show all
Defined in:
lib/volt/page/bindings/if_binding.rb

Instance Attribute Summary

Attributes inherited from BaseBinding

#binding_name, #context, #target

Instance Method Summary collapse

Methods inherited from BaseBinding

#dom_section, #remove_anchors

Constructor Details

#initialize(page, target, context, binding_name, branches) ⇒ IfBinding

Returns a new instance of IfBinding.



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# File 'lib/volt/page/bindings/if_binding.rb', line 5

def initialize(page, target, context, binding_name, branches)
  super(page, target, context, binding_name)

  getter, template_name = branches[0]

  @branches  = []
  @listeners = []

  branches.each do |branch|
    getter, template_name = branch

    if getter.present?
      value = getter
    else
      # A nil value means this is an unconditional else branch, it
      # should always be true
      value = true
    end

    @branches << [value, template_name]
  end

  # The promise dependency can be invalidated when we need to rerun the update
  # manually because a promise resolved.
  @promise_dependency = Dependency.new

  @computation = -> do
    @promise_dependency.depend

    update
  end.watch!
end

Instance Method Details

#remove ⇒ Object 



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# File 'lib/volt/page/bindings/if_binding.rb', line 96

def remove
  @computation.stop if @computation
  @computation = nil

  @template.remove if @template

  super
end

#update ⇒ Object 



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# File 'lib/volt/page/bindings/if_binding.rb', line 38

def update
  # Find the true branch
  true_template = nil
  @branches.each do |branch|
    value, template_name = branch

    if value.is_a?(Proc)
      begin
        current_value = @context.instance_eval(&value)

        if current_value.is_a?(Promise)
          # If we got a promise, use its value if resolved.
          if current_value.resolved?
            # Should call then immediately
            current_value.then do |value|
              current_value = value
            end
          else
            # if its not, resolve it and try again.
            # TODO: we maybe could cache this so we don't have to run a full update again
            current_value.then do |val|
              # Run update again
              @promise_dependency.changed!
            end

            current_value = nil
          end
        end
      rescue => e
        Volt.logger.error("IfBinding:#{object_id} error: #{e.inspect}\n" + `value.toString()`)
        current_value = false
      end
    else
      current_value = value
    end

    if current_value && !current_value.is_a?(Exception)
      # This branch is currently true
      true_template = template_name
      break
    end
  end

  # Change out the template only if the true branch has changed.
  if @last_true_template != true_template
    @last_true_template = true_template

    if @template
      @template.remove
      @template = nil
    end

    if true_template
      @template = TemplateRenderer.new(@page, @target, @context, binding_name, true_template)
    end
  end
end