Struct objc2::foundation::NSValue

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#[repr(C)]
pub struct NSValue { /* private fields */ }

Available on crate feature foundation only.

Expand description

A container wrapping any encodable type as an Obective-C object.

Since Objective-C collections like NSArray can only contain objects, it is common to wrap pointers or structures like NSRange.

Note that creating NSValues is not unsafe, but almost all usage of it is, since we cannot guarantee that the type that was used to construct it is the same as the expected output type.

See also the NSNumber subclass for when you want to wrap numbers.

See Apple’s documentation for more information.

Implementations

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impl NSValue

Getter methods.

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pub unsafe fn get<T: 'static + Copy + Encode>(&self) -> T

Retrieve the data contained in the NSValue.

Note that this is broken on GNUStep for some types, see gnustep/libs-base#216.

Safety

The type of T must be what the NSValue actually stores, and any safety invariants that the value has must be upheld.

Note that it may be, but is not always, enough to simply check whether contains_encoding returns true. For example, NonNull<T> have the same encoding as *const T, but NonNull<T> is clearly not safe to return from this function even if you’ve checked the encoding beforehand.

Examples

Store a pointer in NSValue, and retrieve it again afterwards.

use std::ffi::c_void;
use std::ptr;
use objc2::foundation::NSValue;

let val = NSValue::new::<*const c_void>(ptr::null());
// SAFETY: The value was just created with a pointer
let res = unsafe { val.get::<*const c_void>() };
assert!(res.is_null());

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pub fn contains_encoding<T: 'static + Copy + Encode>(&self) -> bool

Methods from Deref<Target = NSObject>

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pub fn is_kind_of<T: ClassType>(&self) -> bool

Check if the object is an instance of the class, or one of it’s subclasses.

See Apple’s documentation for more details on what you may (and what you may not) do with this information.

Methods from Deref<Target = Object>

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pub fn class(&self) -> &Class

Dynamically find the class of this object.

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pub unsafe fn ivar_ptr<T: Encode>(&self, name: &str) -> *mut T

Returns a pointer to the instance variable / ivar with the given name.

This is similar to UnsafeCell::get, see that for more information on what is and isn’t safe to do.

Usually you will have defined the instance variable yourself with ClassBuilder::add_ivar, the type of the ivar T must match the type used in that.

Attempting to access or modify private implementation details of a class that you do no control using this is not supported, and may invoke undefined behaviour.

Library implementors are strongly encouraged to expose a safe interface to the ivar.

Panics

May panic if the object has no ivar with the given name. May also panic if the type encoding of the ivar differs from the type encoding of T.

This should purely seen as help while debugging and is not guaranteed (e.g. it may be disabled when debug_assertions are off).

Safety

The object must have an instance variable with the given name, and it must be of type T. Any invariants that the object have assumed about the value of the instance variable must not be violated.

No thread syncronization is done on accesses to the variable, so you must ensure that any access to the returned pointer do not cause data races, and that Rust’s mutability rules are not otherwise violated.

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pub unsafe fn ivar<T: Encode>(&self, name: &str) -> &T

Returns a reference to the instance variable with the given name.

See Object::ivar_ptr for more information, including on when this panics.

Safety

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

No thread syncronization is done, so you must ensure that no other thread is concurrently mutating the variable. This requirement can be considered upheld if all mutation happens through Object::ivar_mut (since that takes &mut self).

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pub unsafe fn get_ivar<T: Encode>(&self, name: &str) -> &T

👎Deprecated:

Use Object::ivar instead.

Safety

See Object::ivar.

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pub unsafe fn ivar_mut<T: Encode>(&mut self, name: &str) -> &mut T

Returns a mutable reference to the ivar with the given name.

See Object::ivar_ptr for more information, including on when this panics.

Safety

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

This access happens through &mut self, which means we know it to be the only reference, hence you do not need to do any work to ensure that data races do not happen.

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