Struct magnus::block::Proc

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#[repr(transparent)]
pub struct Proc(_);

Expand description

Wrapper type for a Value known to be an instance of Ruby’s Proc class.

All Value methods should be available on this type through Deref, but some may be missed by this documentation.

Implementations

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impl Proc

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pub fn from_value(val: Value) -> Option<Self>

Return Some(Proc) if val is a Proc, None otherwise.

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pub fn new<F, R>(block: F) -> Self where
F: FnMut(&[Value ], Option<Proc>) -> R,
R: BlockReturn,

Create a new Proc.

Examples

use magnus::{block::Proc, eval};

let proc = Proc::new(|args, _block| {
    let acc = args.get(0).unwrap().try_convert::<i64>()?;
    let i = args.get(1).unwrap().try_convert::<i64>()?;
    Ok(acc + i)
});

let res: bool = eval!("proc.call(1, 2) == 3", proc).unwrap();
assert!(res);

let res: bool = eval!("[1, 2, 3, 4, 5].inject(&proc) == 15", proc).unwrap();
assert!(res);

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pub fn call<A, T>(self, args: A) -> Result<T, Error> where
A: RArrayArgList,
T: TryConvert,

Call the proc with args.

Returns Ok(T) if the proc runs without error and the return value converts into a T, or returns Err if the proc raises or the conversion fails.

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pub fn arity(self) -> i64

Returns the number of arguments self takes.

If self takes no arguments, returns 0. If self takes only required arguments, returns the number of required arguments. If self is a lambda and has optional arguments, or is not a lambda and takes a splat argument, returns -n-1, where n is the number of required arguments. If self is not a lambda, and takes a finite number of optional arguments, returns the number of required arguments. Keyword arguments are considered as a single additional argument, that argument being required if any keyword argument is required.

Examples

use magnus::{block::Proc, eval};

let proc = eval::<Proc>("proc {nil}", ).unwrap();
assert_eq!(proc.arity(), 0);

let proc = eval::<Proc>("proc {|a| a + 1}", ).unwrap();
assert_eq!(proc.arity(), 1);

let proc = eval::<Proc>("proc {|a, b| a + b}", ).unwrap();
assert_eq!(proc.arity(), 2);

let proc = eval::<Proc>("proc {|*args| args.sum}", ).unwrap();
assert_eq!(proc.arity(), -1);

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pub fn is_lambda(self) -> bool

Returns whether or not self is a lambda.

Examples

use magnus::{block::Proc, eval};

let proc = eval::<Proc>("proc {|a, b| a + b}", ).unwrap();
assert!(!proc.is_lambda());

let proc = eval::<Proc>("lambda {|a, b| a + b}", ).unwrap();
assert!(proc.is_lambda());

Methods from Deref<Target = Value>

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pub unsafe fn to_s(&self) -> Result<Cow<'_, str>, Error>

Convert self to a Rust string.

Safety

This may return a direct view of memory owned and managed by Ruby. Ruby may modify or free the memory backing the returned str, the caller must ensure this does not happen.

This can be used safely by immediately calling into_owned on the return value.

Examples

use magnus::{eval, QTRUE};

let value = QTRUE;
// safe as we neve give Ruby a chance to free the string.
let s = unsafe { value.to_s() }.unwrap().into_owned();
assert_eq!(s, "true");

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pub unsafe fn classname(&self) -> Cow<'_, str>

Return the name of self’s class.

Safety

Ruby may modify or free the memory backing the returned str, the caller must ensure this does not happen.

This can be used safely by immediately calling into_owned on the return value.

Examples

use magnus::{eval, RHash};

let value = RHash::new();
// safe as we neve give Ruby a chance to free the string.
let s = unsafe { value.classname() }.into_owned();
assert_eq!(s, "Hash");

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pub fn try_convert<T>(&self) -> Result<T, Error> where
T: TryConvert,

Convert self to the Rust type T.

See the types that TryConvert is implemented on for what this method can convert to.

Examples

use magnus::{eval, Value};

assert_eq!(eval::<Value>("42").unwrap().try_convert::<i64>().unwrap(), 42);
assert_eq!(eval::<Value>("1.23").unwrap().try_convert::<i64>().unwrap(), 1);
assert_eq!(eval::<Value>("1").unwrap().try_convert::<f64>().unwrap(), 1.0);
assert_eq!(eval::<Value>("nil").unwrap().try_convert::<Option<i64>>().unwrap(), None);
assert_eq!(eval::<Value>("42").unwrap().try_convert::<Option<i64>>().unwrap(), Some(42));