Synopsis
- LZX: datapath
- JavaScript: LzDatapath
- Type: Class
- Access: public
- Topic: LFC.Data
- Declared in: WEB-INF/lps/lfc/data/LzDatapath.lzs
Description
Datapaths are used to merge data hierarchies with the hierarchy of an
OpenLaszlo application. This is done using the the XPath syntax supported
by LzDatapointer. When a node is given a
datapath attribute, a datapath with
the given value as its XPath is created. If the datapath retrieves a
node (i.e. it doesn't terminate in an attribute getter or a
() operator) then the node is mapped to that data context
and all child nodes will implicitly share the datacontext, but no
further action is taken. If the datapath retrieves data, rather than
just a node, a few extra things happen. First, the node's
data property is set and the node's
ondata event is sent. Second, the node's
applyData method is called with the data as the
argument. In cases where a datapath matches more than one data node,
the view with the matching datapath is replicated once for each data
node that matches, and a LzReplicationManager takes over
the view's spot in its parent.
A node can only have one datapath, and datapaths always have the name
datapath. Additional options available on datapath such
as pooling and
replication are specified
by writing the datapath tag as a separate node.
Example 6. Mapping data to views using datapaths
<canvas height="120">
<dataset name="testdata">
<Monday temp="Hi 48"> Partly Cloudly </Monday>
<Tuesday temp="Hi 60"> Showers Likely </Tuesday>
<Wednesday temp="Hi 63"> Chance Showers </Wednesday>
<Thursday temp="Hi 58"> Mostly Sunny </Thursday>
<Friday temp="Hi 50"> Clear and Cold </Friday>
</dataset>
<simplelayout spacing="5"/>
<view datapath="testdata:/*">
<view>
<simplelayout axis="x"/>
<text />
<text />
<text />
</view>
</view>
</canvas>
Details
Properties (5)
- datacontrolsvisibility
- pooling
-
This attribute applies to datapaths which match multiple nodes and force replication. See the section on Pooling in the Guide for information about the use of this attribute.
- replication
-
Determines whether to use normal or lazy replication, if the datapath matches more than one node. See the section on Replication in the Guide for information about the use of this attribute.
- sortorder
-
The order to use to sort the dataset if replication occurs. One of
ascendingordescendingto use built in dictionary sort, or a function which compares two strings and returns1if the strings are in order,0if they are the same, and-1if they are out of order. To change this attribute, call the setOrder or setComparator method. - sortpath
Methods (4)
- setComparator()
- setNodes()
-
Normally, replication is started when a datapath xpath binding returns multiple nodes. This function overides that behavior and forces replication, and replicates over the list of nodes supplied to this function. Note that once this function is called, the replication manager is no longer actively bound to the data it replicates over by its xpath (if it had one); henceforth the replication set can *only* be controlled by calling setNodes.
- setOrder()
- updateData()
-
This method is used to transfer any values that may have been edited in a datamapped UI control back to the dataset. If the current datapath's
xpathends in a terminal selector (an attribute,text(), orname()expression), then the datapath attempts to call its parent'supdateDatamethod. If this method is defined, the datapath sets the data element's attribute, text, or name, respectively, toupdateData's return value. The method then calls any otherupdateDataon any datapaths which depend on this one for context. In short, to make datamapping work both ways for a given UI control, define aupdateDatamethod that returns the value for the data mapped to the node. This is already done for the baseLzInputTextclass, but not for any other LFC classes.