Class: 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, #queue_update, #remove_anchors, #value_from_getter

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 4

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?
      # Lookup the value
      value = value_from_getter(getter)

      if value.reactive?
        # Trigger change when value changes
        @listeners << value.on('changed') { update }
      end
    else
      # A nil value means this is an unconditional else branch, it
      # should always be true
      value = true
    end

    @branches << [value, template_name]
  end

  update
end

Instance Method Details

#remove ⇒ Object 



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# File 'lib/volt/page/bindings/if_binding.rb', line 66

def remove
  # Remove all listeners on any reactive values
  @listeners.each(&:remove)

  @template.remove if @template

  super
end

#update ⇒ Object 



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# File 'lib/volt/page/bindings/if_binding.rb', line 35

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

    current_value = value.cur

    # TODO: A bug in opal requires us to check == true
    if current_value.true? == true && !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