Drake
InputPort< T > Class Template Referencefinal

## Detailed Description

### template<typename T> class drake::systems::InputPort< T >

An InputPort is a System resource that describes the kind of input a System accepts, on a given port.

It does not directly contain any runtime input port data; that is always contained in a Context. The actual value will be either the value of an OutputPort to which this is connected, or a fixed value set in a Context.

Template Parameters
 T The scalar type, which must be one of the default scalars.

#include <drake/systems/framework/input_port.h>

## Public Member Functions

template<typename ValueType = Eigen::VectorBlock<const VectorX<T>>>
const ValueType & Eval (const Context< T > &context) const
Returns a reference to the up-to-date value of this input port contained in the given Context. More...

template<typename ValueType >
FixedInputPortValueFixValue (Context< T > *context, const ValueType &value) const
Provides a fixed value for this InputPort in the given Context. More...

bool HasValue (const Context< T > &context) const
Returns true iff this port is connected or has had a fixed value provided in the given Context. More...

const System< T > & get_system () const
Returns a reference to the System that owns this input port. More...

const std::string & get_name () const
Get port name. More...

std::string GetFullDescription () const
Returns a verbose human-readable description of port. More...

InputPortIndex get_index () const
Returns the index of this input port within the owning System. More...

PortDataType get_data_type () const
Returns the port data type. More...

int size () const
Returns the fixed size expected for a vector-valued port. More...

bool is_random () const
Returns true if this is a random port. More...

std::optional< RandomDistributionget_random_type () const
Returns the RandomDistribution if this is a random port. More...

DependencyTicket ticket () const
(Advanced.) Returns the DependencyTicket for this port within the owning System. More...

Does not allow copy, move, or assignment
InputPort (const InputPort &)=delete

InputPortoperator= (const InputPort &)=delete

InputPort (InputPort &&)=delete

InputPortoperator= (InputPort &&)=delete

Public Member Functions inherited from InputPortBase
~InputPortBase () override

InputPortIndex get_index () const
Returns the index of this input port within the owning System. More...

bool is_random () const
Returns true if this is a random port. More...

std::optional< RandomDistributionget_random_type () const
Returns the RandomDistribution if this is a random port. More...

const std::string & get_name () const
Get port name. More...

std::string GetFullDescription () const
Returns a verbose human-readable description of port. More...

PortDataType get_data_type () const
Returns the port data type. More...

int size () const
Returns the fixed size expected for a vector-valued port. More...

DependencyTicket ticket () const
(Advanced.) Returns the DependencyTicket for this port within the owning System. More...

InputPortBase (const InputPortBase &)=delete

InputPortBaseoperator= (const InputPortBase &)=delete

InputPortBase (InputPortBase &&)=delete

InputPortBaseoperator= (InputPortBase &&)=delete

Public Member Functions inherited from PortBase
virtual ~PortBase ()

const std::string & get_name () const
Get port name. More...

std::string GetFullDescription () const
Returns a verbose human-readable description of port. More...

PortDataType get_data_type () const
Returns the port data type. More...

int size () const
Returns the fixed size expected for a vector-valued port. More...

DependencyTicket ticket () const
(Advanced.) Returns the DependencyTicket for this port within the owning System. More...

PortBase (const PortBase &)=delete

PortBaseoperator= (const PortBase &)=delete

PortBase (PortBase &&)=delete

PortBaseoperator= (PortBase &&)=delete

## Friends

class internal::FrameworkFactory

## Additional Inherited Members

Protected Types inherited from InputPortBase
using EvalAbstractCallback = std::function< const AbstractValue *(const ContextBase &)>
Signature of a function suitable for returning the cached value of a particular input port. More...

Protected Member Functions inherited from InputPortBase
InputPortBase (internal::SystemMessageInterface *owning_system, std::string name, InputPortIndex index, DependencyTicket ticket, PortDataType data_type, int size, const std::optional< RandomDistribution > &random_type, EvalAbstractCallback eval)
Provides derived classes the ability to set the base class members at construction. More...

const AbstractValueDoEvalRequired (const ContextBase &context) const
Evaluate this port; throws an exception if the port is not connected. More...

const AbstractValueDoEvalOptional (const ContextBase &context) const
Evaluate this port; returns nullptr if the port is not connected. More...

void ThrowRequiredMissing () const
Throws an exception that this port is not connected, but was expected to be connected (i.e., an Eval caller expected that it was always connected). More...

Protected Member Functions inherited from PortBase
PortBase (const char *kind_string, internal::SystemMessageInterface *owning_system, std::string name, int index, DependencyTicket ticket, PortDataType data_type, int size)
Provides derived classes the ability to set the base class members at construction. More...

int get_int_index () const
Returns the index of this port within the owning System (i.e., an InputPortIndex or OutputPortIndex, but as a bare integer). More...

internal::SystemMessageInterface & get_mutable_system_interface ()
Returns get_system_interface(), but without the const. More...

template<typename ValueType >
const ValueType & PortEvalCast (const AbstractValue &abstract) const
Pull a value of a given type from an abstract value or issue a nice message if the type is not correct. More...

template<typename ValueType , typename T >
const ValueType & PortEvalCast (const BasicVector< T > &basic) const
Downcast a basic vector to a more specific subclass (e.g., as generated by //tools/vector_gen) or issue a nice message if the type is not correct. More...

template<typename ValueType >
const ValueType & ThrowBadCast (const AbstractValue &abstract) const
Reports that the user provided a bad ValueType argument to Eval. More...

template<typename ValueType , typename T >
const ValueType & ThrowBadCast (const BasicVector< T > &basic) const
Reports that the user provided a bad ValueType argument to Eval. More...

void ThrowBadCast (const std::string &value_typename, const std::string &eval_typename) const
Reports that the user provided a bad ValueType argument to Eval. More...

## ◆ InputPort() [1/2]

 InputPort ( const InputPort< T > & )
delete

## ◆ InputPort() [2/2]

 InputPort ( InputPort< T > && )
delete

## ◆ Eval()

 const ValueType& Eval ( const Context< T > & context ) const

Returns a reference to the up-to-date value of this input port contained in the given Context.

This is the preferred way to obtain an input port's value since it will not be recalculated once up to date.

If the value is not already up to date with respect to its prerequisites, it will recalculate an up-to-date value before the reference is returned. The recalculation may be arbitrarily expensive, but Eval() is constant time and very fast if the value is already up to date.

Template Parameters
 ValueType The type of the const-reference returned by this method. When omitted, the return type is an Eigen::VectorBlock (this is only valid when this is a vector-valued port). For abstract ports, the ValueType either can be the declared type of the port (e.g., lcmt_iiwa_status), or else in advanced use cases can be AbstractValue to get the type-erased value.
Returns
reference to the up-to-date value; if a ValueType is provided, the return type is const ValueType&; if a ValueType is omitted, the return type is Eigen::VectorBlock<const VectorX<T>>.
Exceptions
 std::exception if the port is not connected. (Use HasValue() to check first, if necessary.)
Precondition
The input port is vector-valued (when no ValueType is provided).
The input port is of type ValueType (when ValueType is provided).

## ◆ FixValue()

 FixedInputPortValue& FixValue ( Context< T > * context, const ValueType & value ) const

Provides a fixed value for this InputPort in the given Context.

If the port is already connected, this value will override the connected source value. (By "connected" we mean that the port appeared in a DiagramBuilder::Connect() call.)

For vector-valued input ports, you can provide an Eigen vector expression, a BasicVector object, or a scalar (treated as a Vector1). In each of these cases the value is copied into a Value<BasicVector>. If the original value was a BasicVector-derived object, its concrete type is maintained although the stored type is still Value<BasicVector>. The supplied vector must have the right size for the vector port or an std::logic_error is thrown.

For abstract-valued input ports, you can provide any ValueType that is compatible with the model type provided when the port was declared. If the type has a copy constructor it will be copied into a Value<ValueType> object for storage. Otherwise it must have an accessible Clone() method and it is stored using the type returned by that method, which must be ValueType or a base class of ValueType. Eigen objects and expressions are not accepted directly, but you can store then in abstract ports by providing an already-abstract object like Value<MatrixXd>(your_matrix).

The returned FixedInputPortValue reference may be used to modify the input port's value subsequently using the appropriate FixedInputPortValue method, which will ensure that cache invalidation notifications are delivered.

Template Parameters
 ValueType The type of the supplied value object. This will be inferred so no template argument need be specified. The type must be copy constructible or have an accessible Clone() method.
Parameters
 [in,out] context A Context that is compatible with the System that owns this port. [in] value The fixed value for this port. Must be convertible to the input port's data type.
Returns
a reference to the the FixedInputPortValue object in the Context that contains this port's value.
Precondition
context is compatible with the System that owns this InputPort.
value is compatible with this InputPort's data type.

## ◆ get_data_type()

 PortDataType get_data_type

Returns the port data type.

## ◆ get_index()

 InputPortIndex get_index

Returns the index of this input port within the owning System.

For a Diagram, this will be the index within the Diagram, not the index within a LeafSystem whose input port was exported.

## ◆ get_name()

 const std::string& get_name

Get port name.

## ◆ get_random_type()

 std::optional get_random_type

Returns the RandomDistribution if this is a random port.

## ◆ get_system()

 const System& get_system ( ) const

Returns a reference to the System that owns this input port.

Note that for a Diagram input port this will be the Diagram, not the LeafSystem whose input port was exported.

## ◆ GetFullDescription()

 std::string GetFullDescription

Returns a verbose human-readable description of port.

This is useful for error messages or debugging.

## ◆ HasValue()

 bool HasValue ( const Context< T > & context ) const

Returns true iff this port is connected or has had a fixed value provided in the given Context.

Beware that at the moment, this could be an expensive operation, because the value is brought up-to-date as part of this operation.

## ◆ is_random()

 bool is_random

Returns true if this is a random port.

## ◆ operator=() [1/2]

 InputPort& operator= ( InputPort< T > && )
delete

## ◆ operator=() [2/2]

 InputPort& operator= ( const InputPort< T > & )
delete

## ◆ size()

 int size

Returns the fixed size expected for a vector-valued port.

Not meaningful for abstract-valued ports.

## ◆ ticket()

 DependencyTicket ticket

(Advanced.) Returns the DependencyTicket for this port within the owning System.

## ◆ internal::FrameworkFactory

 friend class internal::FrameworkFactory
friend

The documentation for this class was generated from the following file: