Struct ReadEnv

pub struct ReadEnv<T: Message + FromStr = String> {
    pub name: InputPort<String>,
    pub output: OutputPort<T>,
}

A block that reads the value of an environment variable.

Block Diagram

block-beta
    columns 4
    Config space:3
    space:4
    space:4
    ReadEnv space:2 Sink
    Config-- "name" -->ReadEnv
    ReadEnv-- "output" -->Sink

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

Sequence Diagram

sequenceDiagram
    autonumber
    participant BlockA as Another block
    participant ReadEnv.name as ReadEnv.name port
    participant ReadEnv as ReadEnv block
    participant ReadEnv.output as ReadEnv.output port
    participant BlockB as Another block

    BlockA-->>ReadEnv: Connect

    BlockA->>ReadEnv: Message (e.g. "TERM")
    ReadEnv-->>ReadEnv.name: Close
    ReadEnv-->>BlockA: Disconnect
    ReadEnv-->>BlockB: Connect

    ReadEnv->>ReadEnv: Read environment variable
    ReadEnv->>BlockB: Message (e.g. "xterm-256color")

    ReadEnv-->>ReadEnv.output: Close
    ReadEnv-->>BlockB: Disconnect

Examples

Using the block in a system

System::build(|s| {
    let name_param = s.const_string("TERM");
    let env_reader = s.read_env();
    let line_encoder = s.encode_lines();
    let stdout = s.write_stdout();
    s.connect(&name_param.output, &env_reader.name);
    s.connect(&env_reader.output, &line_encoder.input);
    s.connect(&line_encoder.output, &stdout.input);
});

Running the block via the CLI

$ protoflow execute ReadEnv name=TERM

Fields

name: InputPort<String>

The name of the environment variable to read.

output: OutputPort<T>

The output message stream.

Implementations

impl<T: Message + FromStr> ReadEnv<T>

pub fn new(name: InputPort<String>, output: OutputPort<T>) -> Self

impl<T: Message + FromStr + 'static> ReadEnv<T>

pub fn with_system(system: &System) -> Self

Trait Implementations

impl<T: Message + FromStr> Block for ReadEnv<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 + FromStr> BlockDescriptor for ReadEnv<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 parameters(&self) -> Vec<ParameterDescriptor>

A description of this block’s parameters.

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

A description of this block’s I/O ports.

impl<T: Clone + Message + FromStr> Clone for ReadEnv<T>

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<T: Message + FromStr> MaybeLabeled for ReadEnv<T>

fn label(&self) -> Option<Cow<'_, str>>

Returns the human-readable label, if any, of the object.

fn is_labeled(&self) -> bool

Checks whether the object has a human-readable label.

impl<T: Message + FromStr> MaybeNamed for ReadEnv<T>

fn name(&self) -> Option<Cow<'_, str>>

Returns the name, if any, of the object.

fn is_named(&self) -> bool

Checks whether the object has a name.

impl<T: Message + FromStr> StdioSystem for ReadEnv<T>

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