objc-encode

Objective-C type encoding creation and parsing in Rust.

The Objective-C compiler encodes types as strings for usage in the runtime. This crate aims to provide a strongly-typed (rather than stringly-typed) way to create and describe these type encodings without memory allocation in Rust.

Implementing Encode

This crate declares an Encode trait that can be implemented for types that the Objective-C compiler can encode. Implementing this trait looks like:

```rust use objc::{Encode, Encoding};

[cfg(targetpointerwidth = "32")]

type CGFloat = f32;

[cfg(targetpointerwidth = "64")]

type CGFloat = f64;

[repr(C)]

struct CGPoint { x: CGFloat, y: CGFloat, }

unsafe impl Encode for CGPoint { const ENCODING: Encoding<'static> = Encoding::Struct("CGPoint", &[CGFloat::ENCODING, CGFloat::ENCODING]); } ```

For an example of how this works with more complex types, like structs containing structs, see the core_graphics example.

Comparing with encoding strings

An Encoding can be compared with an encoding string from the Objective-C runtime:

```rust use objc::Encode;

assert!(&i32::ENCODING == "i"); ```

Generating encoding strings

Every Encoding implements Display as its string representation. This can be generated conveniently through the to_string method:

```rust use objc::Encode;

asserteq!(i32::ENCODING.tostring(), "i"); ```