Struct protoflow_blocks::Const

pub struct Const<T: Message = String> {
    pub output: OutputPort<T>,
    pub value: T,
}

A block for sending a constant value.

This block sends a constant value on its output port. It can also be used to send a constant value to multiple blocks.

The value to send is specified as a parameter, and can be of any type that implements the Message trait.

The block waits for the output port to be connected before sending the value, and closes the port after the value is sent.

The block does not have any input ports nor state.

Block Diagram

block-beta
    columns 4
    Const space:2 Sink
    Const-- "output" -->Sink

    classDef block height:48px,padding:8px;
    classDef hidden visibility:none;
    class Const block
    class Sink hidden

Sequence Diagram

sequenceDiagram
    autonumber
    participant Const as Const block
    participant Const.output as Const.output port
    participant BlockA as Another block

    Const-->>BlockA: Connect

    Const->>BlockA: Message

    Const-->>Const.output: Close
    Const-->>BlockA: Disconnect

Examples

Using the block in a system

System::build(|s| {
    let const_value = s.const_string("Hello, world!");
    let line_encoder = s.encode_lines();
    let stdout = s.write_stdout();
    s.connect(&const_value.output, &line_encoder.input);
    s.connect(&line_encoder.output, &stdout.input);
});

Running the block via the CLI

$ protoflow execute Const value=Hello

Fields

output: OutputPort<T>

The port to send the value on.

value: T

A parameter for the value to send.

Implementations

impl<T: Message + Default> Const<T>

pub fn new(output: OutputPort<T>) -> Self

impl<T: Message> Const<T>

pub fn with_params(output: OutputPort<T>, value: T) -> Self

Trait Implementations

impl<T: Message> Block for Const<T>

fn execute(&mut self, runtime: &dyn BlockRuntime) -> BlockResult

Executes this block’s computation.

fn prepare(&mut self, _runtime: &dyn BlockRuntime) -> Result<(), BlockError>

Prepares this block for execution.

impl<T: Message> BlockDescriptor for Const<T>

fn inputs(&self) -> Vec<PortDescriptor>

A description of this block’s input ports.

fn outputs(&self) -> Vec<PortDescriptor>

A description of this block’s output ports.

fn name(&self) -> Option<String>

The machine-readable name of this block.

fn label(&self) -> Option<String>

A human-readable label for this block.

impl<T: Clone + Message> Clone for Const<T>

fn clone(&self) -> Const<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Message> Definition for Const<T>

fn is_variation(&self) -> bool

impl<T: Message> Element for Const<T>

fn id(&self) -> Option<&str>

The unique element ID, if any.

fn alias_ids(&self) -> Vec<&str>

Various alternative identifiers for this Element.

fn name(&self) -> Option<&str>

The name of the element.

fn short_name(&self) -> Option<&str>

The short name of the element, if any.

fn is_library_element(&self) -> bool

Whether this Element is contained in the ownership tree of a library model.

fn owner(&self) -> Option<&dyn Element>

The owner of this Element, if any.

fn owning_namespace(&self) -> Option<&dyn Namespace>

The Namespace that owns this Element, if any.

fn owning_relationship(&self) -> Option<&dyn Relationship>

The Relationship for which this Element is an owned_related_element, if any.

fn qualified_name(&self) -> Option<QualifiedName>

impl<T: Message> Namespace for Const<T>

fn names_of(&self, _element: &dyn Element) -> Vec<String>

impl<T: Message> OccurrenceDefinition for Const<T>

fn is_individual(&self) -> bool

impl<T: Message> StdioSystem for Const<T>

fn build_system(config: StdioConfig) -> Result<System, StdioError>

impl<T: Message> Type for Const<T>

fn is_abstract(&self) -> bool

fn is_sufficient(&self) -> bool

fn is_conjugated(&self) -> bool

fn specializes(&self, _supertype: &Self) -> bool

impl<T: Message> BlockDefinition for Const<T>

impl<T: Message> Class for Const<T>

impl<T: Message> Classifier for Const<T>

impl<T: Message> ItemDefinition for Const<T>

impl<T: Message> PartDefinition for Const<T>

impl<T: Message> Structure for Const<T>