Struct ClosureEval 

pub struct ClosureEval { /* private fields */ }

ClosureEval is used to repeatedly evaluate a closure with different values/inputs.

ClosureEval has a builder API. It is first created via ClosureEval::new, then has arguments added via ClosureEval::add_arg, and then can be run using ClosureEval::run_with_input.

let mut closure = ClosureEval::new(engine_state, stack, closure);
let iter = Vec::<Value>::new()
    .into_iter()
    .map(move |value| closure.add_arg(value).unwrap().run_with_input(PipelineData::empty()));

Many closures follow a simple, common scheme where the pipeline input and the first argument are the same value. In this case, use ClosureEval::run_with_value:

let mut closure = ClosureEval::new(engine_state, stack, closure);
let iter = Vec::<Value>::new()
    .into_iter()
    .map(move |value| closure.run_with_value(value));

Environment isolation and other cleanup is handled by ClosureEval, so nothing needs to be done following ClosureEval::run_with_input or ClosureEval::run_with_value.

In contrast to ClosureEvalOnce, ClosureEval holds an owned copy of the EngineState supplied. This makes it possible to return it from a function that only has a borrowed EngineState reference, such as the run function of a [nu_engine::command_prelude::Command] implementation.

Implementations

impl ClosureEval

pub fn new(engine_state: &EngineState, stack: &Stack, closure: Closure) -> Self

Create a new ClosureEval.

pub fn new_preserve_out_dest( engine_state: &EngineState, stack: &Stack, closure: Closure, ) -> Self

pub fn debug(&mut self, debug: bool) -> &mut Self

Sets whether to enable debugging when evaluating the closure.

By default, this is controlled by the EngineState used to create this ClosureEval.

pub fn add_arg(&mut self, value: Value) -> Result<&mut Self, ShellError>

Add an argument Value to the closure.

Multiple add_arg calls can be chained together, but make sure that arguments are added based on their positional order.

pub fn run_with_input( &mut self, input: PipelineData, ) -> Result<PipelineData, ShellError>

Run the closure, passing the given PipelineData as input.

Any arguments should be added beforehand via add_arg.

pub fn run_with_value( &mut self, value: Value, ) -> Result<PipelineData, ShellError>

Run the closure using the given Value as both the pipeline input and the first argument.

Using this function after or in combination with add_arg is most likely an error. This function is equivalent to self.add_arg(value) followed by self.run_with_input(value.into_pipeline_data()).

pub fn run_with_value_with_metadata( &mut self, value: Value, metadata: Option<PipelineMetadata>, ) -> Result<PipelineData, ShellError>

Run the closure using the given Value as both the pipeline input with metadata and the first argument.

Using this function after or in combination with add_arg is most likely an error. This function is equivalent to self.add_arg(value) followed by self.run_with_input(value.into_pipeline_data_with_metadata(metadata)).

Trait Implementations

impl Clone for ClosureEval

fn clone(&self) -> ClosureEval

Returns a duplicate of the value.

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

Performs copy-assignment from source.