Class: GraphTraversal

GraphTraversal

A GraphTraversal defines a strategy for traversing an AbstractGraph.

The two key components of GraphTraversal are a set of states and a set of VisitFunctions, both of which the user of this class must define. States are Strings that indicate the state of the current traversal. VisitFunctions perform arbitrary operations given the current node the GraphTraversal is visiting.

You can associate visitFunctions with states so that different VisitFunctions are invoked when the traversal is in different states.

Consider the following example: You want to traverse from head towards tail the nodes of host "a" until you find a node n that communicates with host "b". After that, you want to traverse from n to head the nodes of host "b". There might be two states: "on a" and "on b". The VisitFunctions for the two states might be as follows: 

'on a':
function(graphTraversal, node, state, data) {
    if(node.getChildByHost('b') != null) {
        graphTraversal.setCurrentNode(node.getChildByHost('b'));
        graphTraversal.setState('on b');
    }
    else {
        graphTraversal.setCurrentNode(node.getNext());
    }
}

'on b':
function(graphTraversal, node, state, data) {
    if(!node.isHead()) {
        graphTraversal.setCurrentNode(node.getPrev());
    }
}

Alternately, you could chose to only define a defaultVisitFunction and decide what should be done based on the state variable

Constructor

new GraphTraversal()

Constructs a GraphTraversal
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Methods

end()

Ends the traversal. After this method is invoked, no more nodes will be visited.
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getTrail(node) → {Array.<AbstractNode>}

Gets the "trail" of nodes, starting at the one provided. The trail is list of nodes that were visited in order to get the the parameter.
Parameters:
Name Type Description
node AbstractNode
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Returns:
Type
Array.<AbstractNode>

hasEnded() → {Boolean}

Determines if this traversal has ended
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Returns:
true is this traversal has ended
Type
Boolean

reset()

Resets the state of the traversal. Bound visit functions will not be touched.
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run() → {*}

"Runs" the traversal. The traversal will be continuously stepped though (i.e with step()) until the traversal has ended. The value returned by the last call to step will be returned by this method.
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Returns:
The value returned by the last call to step, or null if step was never invoked.
Type
*

setCurrentData(data)

Sets the current data. The current data is an object that will be passed to the visit function the next time it's invoked. It can be used to pass arbitrary data
Parameters:
Name Type Description
data *
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setCurrentNode(node)

Sets the current node - the node that will be visited next.
Parameters:
Name Type Description
node AbstractNode
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setDefaultVisitFunction(fn)

Sets the default visit function. The default visit function will be invoked if there is no other visit function bound to the current state, OR if the current state is null.
Parameters:
Name Type Description
fn GraphTraversal~visitFunction The visit function to set as default
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setState(state)

Sets the current state
Parameters:
Name Type Description
state String
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setVisitFunction(state, fn)

Sets the visit function for a state. The visit function will be invoked when the GraphTraversal is in the given state. If there was previously a visit function already defined for the state, it will be replaced.
Parameters:
Name Type Description
state String The state
fn GraphTraversal~visitFunction The visit function
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step() → {*}

Executes a single step of the traversal. The correct VisitFunction is fetched and is executed. If there is a VisitFunction associated with the current state (i.e via a previous call to setVisitFunction) and the current state is not null, then that VisitFunction is invoked. Otherwise, the default visit function is invoked. Whatever is returned by the VisitFunction will be returned by this method

If this traversal has already ended, then this method does nothing and returns null

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Returns:
The return value of the VisitFunction if one was executed, or null otherwise
Type
*

(protected) stepInner() → {*}

This protected function is what actually executes the step. GraphTraversal#step performs some validation and then calls this function. Typically, classes extending this class will override this method to specify what happens during each "step"
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Returns:
The return value of the VisitFunction if one was executed, or null otherwise
Type
*

Type Definitions

VisitFunction(gt, node, state, data)

A VisitFunction is invoked each time the GraphTraversal encounters a new node. Which VisitFunction is invoked depends on what state the GraphTraversal is in.
Parameters:
Name Type Description
gt GraphTraversal The GraphTraversal object invoking the function
node AbstractNode The current node being visited
state String The current state
data Object The current data object.
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