Class: IfBinding

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

Instance Attribute Summary

Attributes inherited from BaseBinding

#binding_name, #context, #target

Instance Method Summary collapse

Methods inherited from BaseBinding

#queue_update, #remove_anchors, #section, #value_from_getter

Constructor Details

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

Returns a new instance of IfBinding.



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# File 'lib/volt/templates/if_binding.rb', line 4

def initialize(target, context, binding_name, branches)
  getter, template_name = branches[0]
  # puts "New If Binding: #{binding_name}, #{getter.inspect}"


  super(target, context, binding_name)

  @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/templates/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/templates/if_binding.rb', line 37

def update
  # Find the true branch
  true_template = nil
  @branches.each do |branch|
    value, template_name = branch
    
    # TODO: A bug in opal requires us to check == true
    if value.cur.true? == true
      # 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(@target, @context, binding_name, true_template)
    end
  end
end