Struct ClosureEvalOnce 

pub struct ClosureEvalOnce<'a> { /* private fields */ }

ClosureEvalOnce is used to evaluate a closure a single time.

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

let result = ClosureEvalOnce::new(engine_state, stack, 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 ClosureEvalOnce::run_with_value:

let result = ClosureEvalOnce::new(engine_state, stack, closure).run_with_value(value);

In contrast to ClosureEval, the lifetime of ClosureEvalOnce is bound to that of the supplied EngineState reference, which makes it more light-weight.

Implementations

impl<'a> ClosureEvalOnce<'a>

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

Create a new ClosureEvalOnce.

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

pub fn new_env_preserve_out_dest( engine_state: &'a EngineState, stack: &'a mut Stack, closure: Closure, ) -> Self

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

Sets whether to enable debugging when evaluating the closure.

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

pub fn add_arg(self, value: Value) -> Result<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 add_args(self, values: Vec<Value>) -> Result<Self, ShellError>

Add a list of argument Values to the closure.

pub fn run_with_input( 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(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( 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)).