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NAME
SoField — base class for all fields
INHERITS FROM
SoField
SYNOPSIS
#include <Inventor/fields/SoField.h>
Methods from class SoField:
void setIgnored(SbBool ignore)
SbBool isIgnored() const
SbBool isDefault() const
static SoType getClassTypeId()
virtual SoType getTypeId() const
virtual SbBool isOfType(SoType type) const
SbBool set(const char *valueString)
void get(SbString &valueString)
int operator ==(const SoField &f) const
int operator !=(const SoField &f) const
void touch()
SbBool connectFrom(SoField *fromField)
SbBool connectFrom(SoEngineOutput *fromEngine)
void disconnect()
SbBool isConnected() const
SbBool isConnectedFromField() const
SbBool getConnectedField(SoField *&writingField) const
SbBool isConnectedFromEngine() const
SbBool getConnectedEngine(SoEngineOutput *&engineOutput) const
void enableConnection(SbBool flag)
SbBool isConnectionEnabled() const
int getForwardConnections(SoFieldList &list) const
SoFieldContainer * getContainer() const
DESCRIPTION
SoField is the abstract base class for all fields. Fields are the data elements contained
within nodes and are the input values for engines. Each node or engine class specifies a
set of fields and associates a name with each. These names define the semantics of the
field (e.g., the SoCube node contains three float fields named width, height, and depth).
Field classes provide the access methods that indirectly allow editing and querying of
data within nodes.
There are two abstract subclasses of SoField: SoSField is the base class for all single-
valued field classes and SoMField is the base class for all multiple-valued fields, which
contain dynamic arrays of values. Subclasses of SoSField have an SoSF prefix, and
subclasses of SoMField have an SoMF prefix. See the reference pages for SoSField and
SoMField for additional methods.
Fields are typically constructed only within node or engine instances; if you need a field
that is not part of a node or engine, you can create a GlobalField; see the methods on
SoDB for creating global fields.
Fields can be connected either directly to another field, or can be connected to the
output of an engine. The value of a field with a connection will change when the thing it
is connected to changes. For example, consider a field "A" that is connected from "B" (by
A->connectFrom(B)). When B's value is changed, A's value will also change. Note that A and
B may have different values, even if they are connected: if A's value is set after B's
value, A's value will be different from B's until B's value is set.
A field can be connected to several other fields, but can be connected from only one
source.
It is possible (and often useful) to create loops of field connections (for example, A
connected from B and B connected from A). If there are loops, then the rule is that the
last setValue() done overrides any connections in to that value. You can think of setting
the value of a field as immediately propagating that value forward into all the fields it
is connected to, with the propagation stopping at the place where the original setValue()
occurred if there is a connection loop. (Actually, a more efficient mechanism than this is
used, but the semantics are the same.)
If you try to connect two fields of differing types, Inventor will automatically try to
insert a field converter engine between them to convert values from one type into the
other. Inventor has most reasonable conversions built-in (multiple-valued field to single-
valued and vice versa, anything to SoSFString, anything to SoSFTrigger,
float/short/unsigned short/int32_t/uint32_t/etc numeric conversions, etc). You can add
field converters using SoDB's extender method addConverter(); see the SoDB.h header file
for details. You can also find out if a converter is available with the
SoDB::getConverter() method.
Fields each define their own file format for reading and being written to files, but all
fields follow the same conventions:
Fields in a node or engine are written as the name of the field followed by the field's
value; fields are not written if they have not been modified since they were created (if
they have their default value).
The ignored flag is written as a "~" character after the field's value (if the field's
value is its default value, just the "~" is written).
Field connections are written as an "=" followed by the container of the field or engine
output that the field is connected to, followed by a "." and the name of the field or
engine output. For example:
DEF node1 Transform { translation 1 1 1 }
DEF node2 Scale { scaleFactor 1 1 1 = USE node1.translation }
Global fields are written as part of an internal SoFieldContainer class called GlobalField,
which writes out an SoSFName field named type whose value is the type of the global field,
followed by a field of that type whose name is the name of the global field. For example, a
global uint32_t field called "FrameCounter" whose value is 494 would be written as:
GlobalField {
type SoSFUInt32
FrameCounter 494
}
METHODS
void setIgnored(SbBool ignore)
SbBool isIgnored() const
Sets/gets the ignore flag for this field. When a field's ignore flag is set to TRUE,
the field is not used during traversal for rendering and other actions. The default
value for this flag is FALSE.
SbBool isDefault() const
Gets the state of default flag of the field. This flag will be TRUE for any field whose
value is not modified after construction and will be FALSE for those that have changed
(each node or engine determines what the default values for its fields are). Note: the
state of this flag should not be set explicitly from within applications.
static SoType getClassTypeId()
Return the type identifier for this field class.
virtual SoType getTypeId() const
Return the type identifier for this field instance (SoField *).
virtual SbBool isOfType(SoType type) const
Returns TRUE if this field is the given type or derived from that type. This is
typically used with the getClassTypeId() method to determine the type of an SoField *
at run-time:
SoField *field = ....;
if (field->isOfType(SoSFFloat::getClassTypeId())) {
SoSFFloat *floatField = (SoSFFloat *)field);
floatField->setValue(4.5);
}
SbBool set(const char *valueString)
Sets the field to the given value, which is an ASCII string in the Inventor file
format. Each field subclass defines its own file format; see their reference pages for
information on their file format. The string should contain only the field's value,
not the field's name (e.g., "1.0", not "width 1.0"). This method returns TRUE if the
string is valid, FALSE if it is not.
void get(SbString &valueString)
Returns the value of the field in the Inventor file format, even if the field has its
default value.
int operator ==(const SoField &f) const
int operator !=(const SoField &f) const
Return TRUE (FALSE) if this field is of the same type and has the same value as f.
void touch()
Simulates a change to the field, causing attached sensors to fire, connected fields and
engines to be marked as needing evaluation, and so forth. Calling touch() on an
instance of a derived field class is equivalent to calling setValue(getValue()) using
the derived class's methods, except that the field's isDefault() status remains
unchanged.
SbBool connectFrom(SoField *fromField)
SbBool connectFrom(SoEngineOutput *fromEngine)
Connects this field to another field or from an engine output. If the field was
connected to something before, it will be automatically disconnected (a field may have
only one connection writing into it at a time). Unless connections to the field are
disabled (see enableConnection()), the field's value will be set to the value of the
thing it is connected to.
void disconnect()
Disconnect the field from whatever it was connected to. This does nothing if the field
was not connected.
SbBool isConnected() const
Returns TRUE if the field is connected to anything.
SbBool isConnectedFromField() const
Returns TRUE if the field is connected to another field.
SbBool getConnectedField(SoField *&writingField) const
Returns TRUE if this field is being written into by another field, and returns the
field it is connected to in writingField. Returns FALSE and does not modify
writingField if it is not connected to a field.
SbBool isConnectedFromEngine() const
Returns TRUE if the field is connected to an engine's output.
SbBool getConnectedEngine(SoEngineOutput *&engineOutput) const
Returns TRUE if this field is being written into by an engine, and returns the engine
output it is connected to in engineOutput. Returns FALSE and does not modify
engineOutput if it is not connected to an engine.
void enableConnection(SbBool flag)
Field connections may be enabled and disabled. Disabling a field's connection is almost
exactly like disconnecting it; the only difference is that you can later re-enable the
connection by calling enableConnection(TRUE). Note that disconnecting an engine output
can cause the engine's reference count to be decremented and the engine to be deleted,
but disabling the connection does not decrement its reference count.
Re-enabling a connection will cause the value of the field to be changed to the engine
output or field to which it is connected.
A field's connection-enabled status is maintained even if the field is disconnected or
reconnected. By default, connections are enabled.
SbBool isConnectionEnabled() const
Returns FALSE if connections to this field are disabled. Note that this may return
FALSE even if the field is not connected to anything.
int getForwardConnections(SoFieldList &list) const
Adds pointers to all of the fields that this field is writing into (either fields in
nodes, global fields or engine inputs) to the given field list, and returns the number
of forward connections.
SoFieldContainer * getContainer() const
Returns the object that contains this field. The type of the object will be either
SoNode, SoEngine, or will be a global field container (note that the global field
container class is internal to Inventor; see the methods for creating and accessing
global fields on SoDB). For example:
SoFieldContainer *f = field->getContainer();
if (f->isOfType(SoNode::getClassTypeId())) {
... do something ...
} else if (f->isOfType(SoEngine::getClassTypeId())) {
... do someting else ...
} else {
... it must be a global field. We can figure out its name, but
that is about it:
const SbName &globalFieldName = f->getName();
}
SEE ALSO
SoSField, SoMField, SoNode, SoDB
SoField(3IV)()