UsdSchemaBase

Fully qualified name: usdrt::UsdSchemaBase

class UsdSchemaBase

Base class for all Usd Schemas. Schema objects hold a UsdPrim m_prim and an SdfPath m_primPath and provide an additional layer of specific API.

Create vs Get Property Methods

For a UsdAttribute named “points” defined in a schema class, you will find two access methods in the schema class in C++ and python:

• GetPointsAttr()

• CreatePointsAttr()

GetPointsAttr() returns a UsdAttribute and is used in read-only cases.

CreatePointsAttr() returns a UsdAttribute, and also creates it on the prim if it doesn’t exist. There is no change if the attribute already exists.

Subclassed by usdrt::UsdAPISchemaBase, usdrt::UsdTyped

Public Functions

explicit UsdSchemaBase(const UsdPrim &prim = UsdPrim())

Construct and store prim as the held prim.

Parameters:

prim – The help prim in this schema.

explicit UsdSchemaBase(const UsdSchemaBase &otherSchema)

Construct and store for the same prim held by otherSchema.

Parameters:

otherSchema – Other schema to copy.

virtual ~UsdSchemaBase()

Destructor.

UsdPrim GetPrim() const

Return this schema object’s held prim.

SdfPath GetPath() const

Return the SdfPath to this schema object’s held prim.

inline explicit operator bool() const

Check if this schema object is compatible with it’s held prim and that the prim is valid.

A typed schema object is compatible if the held prim’s type is or is a subtype of the schema’s type. Based on prim.IsA().

An API schema object is compatible if the API is of type SingleApplyAPI or UsdSchemaType::MultipleApplyAPI, and the schema has been applied to the prim. Based on prim.HasAPI.

This method invokes polymorphic behaviour.

See also

UsdSchemaBase::_IsCompatible()

Returns:

True if the help prim is valid, and the schema object is compatible with its held prim.

Public Static Functions

static inline const TfToken _GetStaticTfType()

Return the type of schema this class is.

See also

UsdSchemaBase::schemaType

Note

This diverges from Usd and returns a TfToken, since we don’t implement TfType.

Public Static Attributes

static const UsdSchemaType schemaType = UsdSchemaType::AbstractBase

Compile time constant representing what kind of schema this class is.

See also

See UsdSchemaType in usd/common.h

Protected Functions

virtual bool _IsCompatible() const

Helper for subclasses to do specific compatibility checking with the given prim. Subclassess may override _isCompatible to for example check type compatibility or value compatibility on the prim.

Overrides exist for UsdTyped and UsdAPISchemaBase.

This check is called when clients invoke the bool operator.

Returns:

True if the schema object is compatible with its held prim.

inline const TfToken _GetType() const

Helper for subclasses to get this schema’s type token.

Note

This diverges from Usd and returns a TfToken, since we don’t implements TfType.

Returns:

The token representing the schema’s TfType.