Struct JSVirtualMachine

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#[repr(C)]
pub struct JSVirtualMachine { /* private fields */ }
Available on crate features JSVirtualMachine and objc2 only.
Expand description

An instance of JSVirtualMachine represents a single JavaScript “object space” or set of execution resources. Thread safety is supported by locking the virtual machine, with concurrent JavaScript execution supported by allocating separate instances of JSVirtualMachine.

A virtual machine may need to run deferred tasks on a run loop, such as garbage collection or resolving WebAssembly compilations. By default, a virtual machine will use the run loop of the thread it was initialized on. Currently, there is no API to change a JSVirtualMachine’s run loop once it has been initialized.

See also Apple’s documentation

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impl JSVirtualMachine

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pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>

Create a new JSVirtualMachine.

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pub unsafe fn addManagedReference_withOwner( &self, object: Option<&AnyObject>, owner: Option<&AnyObject>, )

Notify the JSVirtualMachine of an external object relationship.

Allows clients of JSVirtualMachine to make the JavaScript runtime aware of arbitrary external Objective-C object graphs. The runtime can then use this information to retain any JavaScript values that are referenced from somewhere in said object graph.

For correct behavior clients must make their external object graphs reachable from within the JavaScript runtime. If an Objective-C object is reachable from within the JavaScript runtime, all managed references transitively reachable from it as recorded using -addManagedReference:withOwner: will be scanned by the garbage collector.

Parameter object: The object that the owner points to.

Parameter owner: The object that owns the pointed to object.

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pub unsafe fn removeManagedReference_withOwner( &self, object: Option<&AnyObject>, owner: Option<&AnyObject>, )

Notify the JSVirtualMachine that a previous object relationship no longer exists.

The JavaScript runtime will continue to scan any references that were reported to it by -addManagedReference:withOwner: until those references are removed.

Parameter object: The object that was formerly owned.

Parameter owner: The former owner.

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impl JSVirtualMachine

Methods declared on superclass NSObject.

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pub unsafe fn new() -> Retained<Self>

Methods from Deref<Target = NSObject>§

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pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

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pub fn class(&self) -> &'static AnyClass

Dynamically find the class of this object.

§Panics

May panic if the object is invalid (which may be the case for objects returned from unavailable init/new methods).

§Example

Check that an instance of NSObject has the precise class NSObject.

use objc2::ClassType;
use objc2::runtime::NSObject;

let obj = NSObject::new();
assert_eq!(obj.class(), NSObject::class());
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pub unsafe fn get_ivar<T>(&self, name: &str) -> &T
where T: Encode,

👎Deprecated: this is difficult to use correctly, use Ivar::load instead.

Use Ivar::load instead.

§Safety

The object must have an instance variable with the given name, and it must be of type T.

See Ivar::load_ptr for details surrounding this.

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pub fn downcast_ref<T>(&self) -> Option<&T>
where T: DowncastTarget,

Attempt to downcast the object to a class of type T.

This is the reference-variant. Use Retained::downcast if you want to convert a retained object to another type.

§Mutable classes

Some classes have immutable and mutable variants, such as NSString and NSMutableString.

When some Objective-C API signature says it gives you an immutable class, it generally expects you to not mutate that, even though it may technically be mutable “under the hood”.

So using this method to convert a NSString to a NSMutableString, while not unsound, is generally frowned upon unless you created the string yourself, or the API explicitly documents the string to be mutable.

See Apple’s documentation on mutability and on isKindOfClass: for more details.

§Generic classes

Objective-C generics are called “lightweight generics”, and that’s because they aren’t exposed in the runtime. This makes it impossible to safely downcast to generic collections, so this is disallowed by this method.

You can, however, safely downcast to generic collections where all the type-parameters are AnyObject.

§Panics

This works internally by calling isKindOfClass:. That means that the object must have the instance method of that name, and an exception will be thrown (if CoreFoundation is linked) or the process will abort if that is not the case. In the vast majority of cases, you don’t need to worry about this, since both root objects NSObject and NSProxy implement this method.

§Examples

Cast an NSString back and forth from NSObject.

use objc2::rc::Retained;
use objc2_foundation::{NSObject, NSString};

let obj: Retained<NSObject> = NSString::new().into_super();
let string = obj.downcast_ref::<NSString>().unwrap();
// Or with `downcast`, if we do not need the object afterwards
let string = obj.downcast::<NSString>().unwrap();

Try (and fail) to cast an NSObject to an NSString.

use objc2_foundation::{NSObject, NSString};

let obj = NSObject::new();
assert!(obj.downcast_ref::<NSString>().is_none());

Try to cast to an array of strings.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);
// This is invalid and doesn't type check.
let arr = arr.downcast_ref::<NSArray<NSString>>();

This fails to compile, since it would require enumerating over the array to ensure that each element is of the desired type, which is a performance pitfall.

Downcast when processing each element instead.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);

for elem in arr {
    if let Some(data) = elem.downcast_ref::<NSString>() {
        // handle `data`
    }
}

Trait Implementations§

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impl AsRef<AnyObject> for JSVirtualMachine

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fn as_ref(&self) -> &AnyObject

Converts this type into a shared reference of the (usually inferred) input type.
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impl AsRef<JSVirtualMachine> for JSVirtualMachine

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fn as_ref(&self) -> &Self

Converts this type into a shared reference of the (usually inferred) input type.
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impl AsRef<NSObject> for JSVirtualMachine

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fn as_ref(&self) -> &NSObject

Converts this type into a shared reference of the (usually inferred) input type.
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impl Borrow<AnyObject> for JSVirtualMachine

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fn borrow(&self) -> &AnyObject

Immutably borrows from an owned value. Read more
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impl Borrow<NSObject> for JSVirtualMachine

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fn borrow(&self) -> &NSObject

Immutably borrows from an owned value. Read more
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impl ClassType for JSVirtualMachine

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const NAME: &'static str = "JSVirtualMachine"

The name of the Objective-C class that this type represents. Read more
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type Super = NSObject

The superclass of this class. Read more
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type ThreadKind = <<JSVirtualMachine as ClassType>::Super as ClassType>::ThreadKind

Whether the type can be used from any thread, or from only the main thread. Read more
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fn class() -> &'static AnyClass

Get a reference to the Objective-C class that this type represents. Read more
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fn as_super(&self) -> &Self::Super

Get an immutable reference to the superclass.
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impl Debug for JSVirtualMachine

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

Formats the value using the given formatter. Read more
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impl Deref for JSVirtualMachine

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type Target = NSObject

The resulting type after dereferencing.
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fn deref(&self) -> &Self::Target

Dereferences the value.
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impl Hash for JSVirtualMachine

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fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl Message for JSVirtualMachine

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fn retain(&self) -> Retained<Self>
where Self: Sized,

Increment the reference count of the receiver. Read more
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impl NSObjectProtocol for JSVirtualMachine

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fn isEqual(&self, other: Option<&AnyObject>) -> bool
where Self: Sized + Message,

Check whether the object is equal to an arbitrary other object. Read more
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fn hash(&self) -> usize
where Self: Sized + Message,

An integer that can be used as a table address in a hash table structure. Read more
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fn isKindOfClass(&self, cls: &AnyClass) -> bool
where Self: Sized + Message,

Check if the object is an instance of the class, or one of its subclasses. Read more
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fn is_kind_of<T>(&self) -> bool
where T: ClassType, Self: Sized + Message,

👎Deprecated: use isKindOfClass directly, or cast your objects with AnyObject::downcast_ref
Check if the object is an instance of the class type, or one of its subclasses. Read more
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fn isMemberOfClass(&self, cls: &AnyClass) -> bool
where Self: Sized + Message,

Check if the object is an instance of a specific class, without checking subclasses. Read more
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fn respondsToSelector(&self, aSelector: Sel) -> bool
where Self: Sized + Message,

Check whether the object implements or inherits a method with the given selector. Read more
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fn conformsToProtocol(&self, aProtocol: &AnyProtocol) -> bool
where Self: Sized + Message,

Check whether the object conforms to a given protocol. Read more
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fn description(&self) -> Retained<NSObject>
where Self: Sized + Message,

A textual representation of the object. Read more
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fn debugDescription(&self) -> Retained<NSObject>
where Self: Sized + Message,

A textual representation of the object to use when debugging. Read more
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fn isProxy(&self) -> bool
where Self: Sized + Message,

Check whether the receiver is a subclass of the NSProxy root class instead of the usual NSObject. Read more
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fn retainCount(&self) -> usize
where Self: Sized + Message,

The reference count of the object. Read more
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impl PartialEq for JSVirtualMachine

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fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl RefEncode for JSVirtualMachine

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const ENCODING_REF: Encoding = <NSObject as ::objc2::RefEncode>::ENCODING_REF

The Objective-C type-encoding for a reference of this type. Read more
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impl DowncastTarget for JSVirtualMachine

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impl Eq for JSVirtualMachine

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<'a, T> AnyThread for T
where T: ClassType<ThreadKind = dyn AnyThread + 'a> + ?Sized,

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fn alloc() -> Allocated<Self>
where Self: Sized + ClassType,

Allocate a new instance of the class. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<P, T> Receiver for P
where P: Deref<Target = T> + ?Sized, T: ?Sized,

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type Target = T

🔬This is a nightly-only experimental API. (arbitrary_self_types)
The target type on which the method may be called.
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> AutoreleaseSafe for T
where T: ?Sized,