4.18.1 MAReader class

The MAReader class reads Maya ASCII files and calls appropriate methods which have to be implemented in a derived class. The content of the file is actually a subset of the Maya Embedded Language (MEL) which is the scripting language implemented inside Maya. The MAReader parses the file, breaks down the content of the file in commands and their arguments and options (expressions are not evaluated). Each MEL command will then trigger a callback method that has to execute the command. These callback methods have to be implemented in a derived class.

There are 12 MEL commands that can appear in a Maya ASCII file^4.2:

file
requires
fileInfo
currentUnit
createNode
setAttr
addAttr
connectAttr
disconnectAttr
parent
select
lockNode

Each command has a number of arguments and can also take options. The callback methods receive the arguments as regular arguments to the method and the options as an additional argument opts which is a dictionary containing the options that were specified in the file. The key is the long name of the option (without leading dash) and the value is a list of strings containing the option values. The number of values and how they have to be interpreted depend on the actual option.

class MAReader( ): Creates an instance of the reader.

filename: The file name (if it could be obtained). This may be used for generating warning or error messages.

linenr: The current line number. This may be used for generating warning or error messages.

abort( ): Aborts reading the current file. This method can be called in handler methods to abort reading the file.

read( f): Read the content of a file. f is either a file like object that can be used to read the content of the file or the name of a file.

begin( ): Callback method that is called before the file is read.

end( ): Callback method that is called after the file was read.

onFile( filename, opts): Reference an external file.

onRequires( product, version): Specify a requirement that is needed to load the file properly. product is a string containing the required software component and version is a string containing the required version of that component.

onFileInfo( keyword, value, opts): Specifies information about the file. keyword and value are both strings.

onCurrentUnit( opts): Specify the units (linear, angular, time) used in the file.

onCreateNode( nodetype, opts): Create a new node. nodetype is a string specifying the type of node that is to be created. The new node will automatically be selected (i.e. subsequent setAttr commands refer to this node).

onSetAttr( attr, vals, opts): Set a node attribute. attr is a string containing the attribute to be set. vals is a list of values. The number of elements and the type of each element depends on the attribute.

onAddAttr( opts): Add a new attribute to the node.

onConnectAttr( srcattr, dstattr, opts): Connect two attributes. srcattr is a string specifiying the attribute that serves as a source and dstattr is the name of the attribute that will receive the value.

onDisconnectAttr( srcattr, dstattr, opts): Break the attribute connection between two attributes.

onParent( objects, parent, opts): Set the parent of one or more nodes. objects is a list of node names and parent the name of the parent.

onSelect( objects, opts): Select a node from a referenced file. objects is a list of strings containing the node names.

onLockNode( objects, opts): Lock/unlock a node. objects is a list of strings containing the node names (the list may be empty).

Footnotes

... file ^4.2: Actually, there could appear any MEL command, but at least Maya will only export files containing the above commands.