Trait Encode

Source

pub unsafe trait Encode {
    const ENCODING: Encoding;
}

Expand description

Types that have an Objective-C type-encoding.

Usually you will want to implement RefEncode as well.

If your type is an opaque type you should not need to implement this; there you will only need RefEncode.

§Safety

The type must be FFI-safe, meaning a C-compatible repr (repr(C), repr(u8), repr(transparent) where the inner types are C-compatible, and so on). See the nomicon on other reprs.

Objective-C will make assumptions about the type (like its size, alignment and ABI) from its encoding, so the implementer must verify that the encoding is accurate.

Concretely, Self::ENCODING must match the result of running @encode in Objective-C with the type in question.

You should also beware of having Drop types implement this, since when passed to Objective-C via objc2::msg_send! their destructor will not be called!

§Examples

Implementing for a struct:

#[repr(C)]
struct MyType {
    a: i32,
    b: f64,
    c: *const c_void,
}

unsafe impl Encode for MyType {
    const ENCODING: Encoding = Encoding::Struct(
        // The name of the type that Objective-C sees.
        "MyType",
        &[
            // Delegate to field's implementations.
            // The order is the same as in the definition.
            i32::ENCODING,
            f64::ENCODING,
            <*const c_void>::ENCODING,
        ],
    );
}

// Note: You would also implement `RefEncode` for this type.

Required Associated Constants§

Source

const ENCODING: Encoding

The Objective-C type-encoding for this type.

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Trait Encode Copy item path

§Safety

§Examples

Required Associated Constants§

const ENCODING: Encoding

Dyn Compatibility§

Implementations on Foreign Types§

impl Encode for f32

const ENCODING: Encoding = Encoding::Float

impl Encode for f64

const ENCODING: Encoding = Encoding::Double

impl Encode for i8

const ENCODING: Encoding = Encoding::Char

impl Encode for i16

const ENCODING: Encoding = Encoding::Short

impl Encode for i32

const ENCODING: Encoding = Encoding::Int

impl Encode for i64

const ENCODING: Encoding = Encoding::LongLong

impl Encode for isize

const ENCODING: Encoding = i32::ENCODING

impl Encode for u8

const ENCODING: Encoding = Encoding::UChar

impl Encode for u16

const ENCODING: Encoding = Encoding::UShort

impl Encode for u32

const ENCODING: Encoding = Encoding::UInt

impl Encode for u64

const ENCODING: Encoding = Encoding::ULongLong

impl Encode for usize

const ENCODING: Encoding = u32::ENCODING

impl Encode for AtomicI8

const ENCODING: Encoding

impl Encode for AtomicI16

const ENCODING: Encoding

impl Encode for AtomicI32

const ENCODING: Encoding

impl Encode for AtomicI64

const ENCODING: Encoding

impl Encode for AtomicIsize

const ENCODING: Encoding

impl Encode for AtomicU8

const ENCODING: Encoding

impl Encode for AtomicU16

const ENCODING: Encoding

impl Encode for AtomicU32

const ENCODING: Encoding

impl Encode for AtomicU64

const ENCODING: Encoding

impl Encode for AtomicUsize

const ENCODING: Encoding

impl Encode for NonZeroI8

const ENCODING: Encoding = i8::ENCODING

impl Encode for NonZeroI16

const ENCODING: Encoding = i16::ENCODING

impl Encode for NonZeroI32

const ENCODING: Encoding = i32::ENCODING

impl Encode for NonZeroI64

const ENCODING: Encoding = i64::ENCODING

impl Encode for NonZeroIsize

const ENCODING: Encoding = isize::ENCODING

impl Encode for NonZeroU8

const ENCODING: Encoding = u8::ENCODING

impl Encode for NonZeroU16

const ENCODING: Encoding = u16::ENCODING

impl Encode for NonZeroU32

const ENCODING: Encoding = u32::ENCODING

impl Encode for NonZeroU64

const ENCODING: Encoding = u64::ENCODING

impl Encode for NonZeroUsize

const ENCODING: Encoding = usize::ENCODING

impl<'a, T: RefEncode + ?Sized> Encode for &'a T

const ENCODING: Encoding = T::ENCODING_REF

impl<'a, T: RefEncode + ?Sized> Encode for &'a mut T

const ENCODING: Encoding = T::ENCODING_REF

impl<Ret: EncodeReturn> Encode for extern "C" fn() -> Ret

const ENCODING: Encoding

impl<Ret: EncodeReturn> Encode for extern "C-unwind" fn() -> Ret

const ENCODING: Encoding

impl<Ret: EncodeReturn> Encode for unsafe extern "C" fn() -> Ret

Trait Encode