SoField(3IV)

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