Struct hcl::eval::Context

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

A type holding the evaluation context.

The Context is used to declare variables and functions that are evaluated when evaluating a template or expression.

Implementations

impl<'a> Context<'a>

pub fn new() -> Self

Creates an empty Context.

pub fn declare_var<I, T>(&mut self, name: I, value: T)

where I: Into<Identifier>, T: Into<Value>,

Declare a variable from a name and a value.

Example

let mut ctx = Context::new();
ctx.declare_var("some_number", 42);

pub fn declare_func<I>(&mut self, name: I, func: FuncDef)

where I: Into<Identifier>,

Declare a function from a name and a function definition.

See the documentation of the FuncDef type to learn about all available options for constructing a function definition.

Example

use hcl::Value;
use hcl::eval::{FuncArgs, FuncDef, ParamType};

fn strlen(args: FuncArgs) -> Result<Value, String> {
    // The arguments are already validated against the function
    // definition's parameters, so we know that there is exactly
    // one arg of type string.
    Ok(Value::from(args[0].as_str().unwrap().len()))
}

let func_def = FuncDef::builder()
    .param(ParamType::String)
    .build(strlen);

let mut ctx = Context::new();
ctx.declare_func("strlen", func_def);

Trait Implementations

impl<'a> Clone for Context<'a>

fn clone(&self) -> Context<'a>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'a> Debug for Context<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Context<'_>

fn default() -> Self

Returns the “default value” for a type.