UITree provides two ways of populating the tree, Instant and Delayed.

Instant

*UITree** has a rootNodes array rule. This should evaluate to an array of UITreeNode objects. This will populate the UITree without additional roundtrips to the server.

Delayed

*UITree** has rootRefchain and rootExpression rules. when the UITree is created, the client will evaluate rootExpression in the rootRefchain model context. The expression must return an array of POJOs in the same form as used in the Instant Data method. Custom UI will populate root level of the tree (one or more nodes) with the data retrieved.

UITreeNode Structure

{
"title": "Name of this Node",
"isExpandable": true|false,
"nodes": [],
"nodesRefChain": "refChain to the model having nodesExpression",
"nodesExpression": "expression returning array of UITreeNodes"
}

These objects can be collected from UITreeNodeMixin models.

There are two alternate ways to specify a tree:

1. By supplying nodes directly. If nodes is supplied, nodesRefChain, nodesExpression, and isExpandable will be ignored.

2. By supplying nodesRefChain and nodesExpression. In this case, if isExpandable is true, the system will request the next level from the server, by using the nodesRefChain and nodesExpression values.

You can combine 'Instant' and 'Delayed' approaches. The above controls work at any level.