---
title: Walking a model tree
---

<p>
    You can traverse a model tree by calling <a href="/docs/api/modules/makerjs.model.html#walk">makerjs.model.walk</a> with your model and an object with these optional properties:

    <table>
        <tr>
            <th>property name</th>
            <th>property type</th>
            <th>description</th>
        </tr>
        <tr>
            <td>onPath</td>
            <td>function(<a href="/docs/api/interfaces/makerjs.iwalkpath.html#content">walkPath</a> object)</td>
            <td>called for every path (in every model) in your tree.</td>
        </tr>
        <tr>
            <td>beforeChildWalk</td>
            <td>function(<a href="/docs/api/interfaces/makerjs.iwalkmodel.html#content">walkModel</a>)</td>
            <td>called for every model in your tree, prior to diving deeper down the tree. <b>Return false if you wish to not dive deeper.</b></td>
        </tr>
        <tr>
            <td>afterChildWalk</td>
            <td>function(<a href="/docs/api/interfaces/makerjs.iwalkmodel.html#content">walkModel</a>)</td>
            <td>called for every model in your tree, after returning from a deep dive down the tree.</td>
        </tr>
    </table>

</p>

<h4>walkPath object</h4>

<p>
    A walkPath object has these properties: 
    <ul>
        <li><b>layer</b>: the layer name (if any) containing this path.</li>
        <li><b>modelContext</b>: the model containing this path.</li>
        <li><b>offset</b>: the absolute coordinates from [0, 0] where this path is located.</li>
        <li><b>pathContext</b>: the path itself.</li>
        <li><b>pathId</b>: the id of this path in its parent model.paths container.</li>
        <li><b>route</b>: array of property names to locate this path from the root of the tree.</li>
        <li><b>routeKey</b>: a string representation of the route which may safely be used as a unique key identifier for this path.</li>
    </ul>
</p>

<h4>walkModel object</h4>

<p>
    A walkModel object has these properties:
    <ul>
        <li><b>childId</b>: the id of this model in its parent model.models container.</li>
        <li><b>childModel</b>: the model itself</li>
        <li><b>layer</b>: the layer name (if any) containing this path.</li>
        <li><b>offset</b>: the absolute coordinates from [0, 0] where this model is located.</li>
        <li><b>parentModel</b>: the model containing this model.</li>
        <li><b>route</b>: array of property names to locate this model from the root of the tree.</li>
        <li><b>routeKey</b>: a string representation of the route which may safely be used as a unique key identifier for this model.</li>
    </ul>
</p>

<h4>Example</h4>

<p>In this example we will create a RoundRectangle and walk its tree. We have an <code>onPath</code> function that will get called for every path in the model. If the path is an arc, we will invert it:</p>

{% highlight javascript %}
//render a model using mixed units
var makerjs = require('makerjs');

function invertArc(arc) {
  var chord = new makerjs.paths.Chord(arc);
  var midPoint = makerjs.point.middle(chord);
  makerjs.path.rotate(arc, 180, midPoint);
}

var shape = new makerjs.models.RoundRectangle(100, 50, 10);

var walkOptions = {
  onPath: function (wp) {
    if (wp.pathContext.type === 'arc') {
      invertArc(wp.pathContext);
    }
  }
};

makerjs.model.walk(shape, walkOptions);
var svg = makerjs.exporter.toSVG(shape);

document.write(svg);
{% endhighlight %}

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