BNodeInfo¶
BNodeInfo provides file type information about a particular node; specifically:
The (MIME) file type.
The node’s icons, including the node-specific icon that the Tracker displays.
The “preferred app”; this is the application that’s used to access the node’s contents.
Except for the Tracker icon, all this information can also be set through
the BNodeInfo class. None of the information is passed on to the
File Type database; if you want to record a node’s file type information
with the database, you have to create a BMimeType object
(based on the node’s file type) and go from there.
Initialization¶
You initialize a BNodeInfo object by passing it a
BNode object. Although you can pass any flavor of node, you
typically only care about files; passing a BFile object (or
any subclass of BNode) is, of course, acceptable. The
BNodeInfo object maintains its own pointer to the BNode you pass
in. You don’t have to avoid touching the BNode while a
BNodeInfo is looking at it (or changing it); the only thing you
shouldn’t do is delete the BNode.
BNodeInfo doesn’t care if the BNode is
locked—there’s no particular reason to lock the BNode before
passing it in, but the BNodeInfo won’t balk if you do. If you
pass in a BFile object, BNodeInfo does not obey the
BFile’s read/write flags. For example, you can set the node
info for a BFile even if you’ve opened it in read-only mode.
Node Info Equals Attributes¶
The BNodeInfo class does nothing more than look in a node’s
attributes for the information it sets or gets. The attribute names for the
various information particles are given in the function descriptions,
below. If you want, you can bypass BNodeInfo and get the node
information directly by passing the attribute names to BNode’s
ReadAttr() and WriteAttr()
functions.
The one exception to this is GetTrackerIcon(): This
function starts by looking in the node’s attributes, but then it goes out
hunting if it has to (if the icon isn’t found in the attributes).
BAppFileInfo¶
BNodeInfo has a single subclass: BAppFileInfo. You
use a BAppFileInfo object to get more information about a
specific executable image (file).
Errors¶
Unlike most of the other Storage Kit classes, when you ask a BNodeInfo to retrieve some information by reference, the object doesn’t clear the reference argument if it fails. Because of this, you should always check the error code that’s returned by the Get…() functions.