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Nasal library/io: Difference between revisions
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== XML == | == Read FG PropertyList XML == | ||
=== io.read_properties() === | |||
Load XML file in FlightGear's native <PropertyList> format. | |||
If the second, optional target parameter is set, then the properties | |||
are loaded to this node in the global property tree. Otherwise they | |||
are returned as a separate props.Node tree. Returns the data as a | |||
props.Node on success or nil on error. | |||
<syntaxhighlight lang="nasal"> | |||
Usage: io.read_properties(<filename> [, <props.Node or property-path>]); | |||
</syntaxhighlight> | |||
Examples: | |||
<syntaxhighlight lang="nasal"> | |||
var target = props.globals.getNode("/sim/model"); | |||
io.read_properties("/tmp/foo.xml", target); | |||
var data = io.read_properties("/tmp/foo.xml", "/sim/model"); | |||
var data = io.read_properties("/tmp/foo.xml"); | |||
</syntaxhighlight> | |||
=== io.read_airport_properties() === | |||
Load XML file in FlightGear's native <PropertyList> format. | |||
File will be located in the airport-scenery directories according to | |||
ICAO and filename, i,e in Airports/I/C/A/ICAO.filename.xml | |||
If the second, optional target parameter is set, then the properties are loaded to this node in the global property tree. | |||
Otherwise they are returned as a separate props.Node tree. | |||
Returns the data as a props.Node on success or nil on error. | |||
<syntaxhighlight lang="nasal"> | |||
Usage: io.read_properties(<filename> [, <props.Node or property-path>]); | |||
</syntaxhighlight> | |||
Example: | |||
<syntaxhighlight lang="nasal"> | |||
var data = io.read_airport_properties("KSFO", "rwyuse"); | |||
</syntaxhighlight> | |||
== Write FG PropertyList XML == | |||
=== io.write_properties() === | |||
Write XML file in FlightGear's native <PropertyList> format. | |||
Returns the filename on success or nil on error. If the source is a props.Node that refers to a node in the main tree, | |||
then the data are directly written from the tree, yielding a more accurate result. | |||
Otherwise the data need to be copied first, which may slightly change node types (FLOAT becomes DOUBLE etc.) | |||
<syntaxhighlight lang="nasal"> | |||
Usage: io.write_properties(<filename>, <props.Node or property-path>); | |||
</syntaxhighlight> | |||
Examples: | |||
<syntaxhighlight lang="nasal"> | |||
var data = props.Node.new({ a:1, b:2, c:{ d:3, e:4 } }); | |||
io.write_properties("/tmp/foo.xml", data); | |||
io.write_properties("/tmp/foo.xml", "/sim/model"); | |||
</syntaxhighlight> | |||
== Read/Write Plain XML == | |||
The following two functions are for reading generic XML files into | |||
the property tree and for writing them from there to the disk. The | |||
built-in fgcommands (load, save, loadxml, savexml) are for FlightGear's | |||
own <PropertyList> XML files only, as they only handle a limited | |||
number of very specific attributes. The io.readxml() loader turns | |||
attributes into regular children with a configurable prefix prepended | |||
to their name, while io.writexml() turns such nodes back into | |||
attributes. The two functions have their own limitations, but can | |||
easily get extended to whichever needs. The underlying parsexml() | |||
command will handle any XML file. | |||
=== io.readxml(path[,prefix = "___"]) === | |||
Reads an XML file from an absolute path and returns it as property | |||
tree. All nodes will be of type STRING. Data are only written to | |||
leafs. Attributes are written as regular nodes with the optional | |||
prefix prepended to the name. If the prefix is nil, then attributes | |||
are ignored. Returns nil on error. | |||
<syntaxhighlight lang="nasal"> | |||
io.readxml(path,prefix); | |||
</syntaxhighlight> | |||
=== io.writexml(path, node[,indent = "\t"][, prefix = "___"]) === | |||
Writes a property tree as returned by readxml() to a file. Children | |||
with name starting with <prefix> are again turned into attributes of | |||
their parent. <node> must contain exactly one child, which will | |||
become the XML file's outermost element. | |||
<syntaxhighlight lang="nasal"> | |||
io.writexml(path, node, indent,prefix); | |||
</syntaxhighlight> | |||
== Serializing Nasal types == | == Serializing Nasal types == | ||