Struct objc2::runtime::Method

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#[repr(C)]
pub struct Method(/* private fields */);

Expand description

A type that represents a method in a class definition.

See Apple’s documentation.

Implementations§

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impl Method

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pub fn name(&self) -> Sel

Returns the name of self.

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pub fn return_type( &self ) -> impl Deref<Target = str> + AsRef<str> + Debug + Display

Returns the Encoding of self’s return type.

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pub fn argument_type( &self, index: usize ) -> Option<impl Deref<Target = str> + AsRef<str> + Debug + Display>

Returns the Encoding of a single parameter type of self, or None if self has no parameter at the given index.

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pub fn arguments_count(&self) -> usize

Returns the number of arguments accepted by self.

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pub fn implementation(&self) -> Imp

Returns the implementation of this method.

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pub unsafe fn set_implementation(&self, imp: Imp) -> Imp

Set the implementation of this method.

Note that any thread may at any point be changing method implementations, so if you intend to call the previous method as returned by e.g. Self::implementation, beware that that may now be stale.

The previous implementation is returned from this function though, so you can call that instead.

See Apple’s documentation.

§Safety

The given implementation function pointer must:

Have the signature expected by the Objective-C runtime and callers of this method.
Be at least as safe as the existing method, i.e. by overriding the previous method, it should not be possible for the program to cause UB.

A common mistake would be expecting e.g. a pointer to not be null, where the null case was handled before.

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pub unsafe fn exchange_implementation(&self, other: &Self)

Exchange the implementation of two methods.

See Apple’s documentation.

§Safety

The two methods must be perfectly compatible, both in signature, and in expected (in terms of safety, not necessarily behaviour) input and output.

§Example

This is an atomic version of the following:

use objc2::runtime::Method;

let m1: &Method;
let m2: &Method;

unsafe {
    let imp = m2.set_implementation(m1.implementation());
    m1.set_implementation(imp);
}