Massage Rails better_nested_set full_set into a hierarchy - JSON

better_nested_set is a great Rails plugin for working with certain types of hierarchical data. The typical example where better_nested_set is used is for a threaded message board. better_nested_set will allow you to pull in a message and all its descendants with a single full_set call. The data that is returned includes a level field that allows you to indent the messages to indicate the appropriate parental relationships.

Sometimes, however, it may be necessary to take that full_set and turn it into a hierarchical data structure. For example when working with Ext JS you may want to feed this data to a tree control that needs a hierarchical JSON representation of the data. Here is some sample code that will do the necessary data massaging:

	# Returns hierarchical data structure rooted at this node. When converting to
	# json make sure to remove :parent to avoid circular reference:
	# message.full_hierarchy.to_json(:only => [:id, :subject, :children, ...])
	def full_hierarchy
	the_full_set = full_set
	ancestry = [build_node(the_full_set.shift)]
	while !the_full_set.empty?
	next_node = build_node(the_full_set.shift)
	while next_node[:level] <= ancestry.last[:level]
	ancestry.pop
	end
	ancestry.last[:children] << next_node
	ancestry.last[:leaf] = false
	next_node[:parent] = ancestry.last
	ancestry << next_node
	end
	ancestry[0]
	end
	private
	# active record Message to node for hierarchy
	def build_node(message)
	ret = {}
	ret[:id] = message.id
	ret[:subject] = message.subject
	ret[:message] = message.message
	ret[:level] = message.level
	ret[:account_id] = message.account_id
	ret[:author] = message.account.login
	ret[:children] = []
	ret[:parent] = nil
	ret[:leaf] = true
	ret
	end

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