#[repr(C)]
pub struct Ivar<T: IvarType> { /* private fields */ }
Expand description

A wrapper type over a custom instance variable.

This type is not meant to be constructed by itself, it must reside within another struct meant to represent an Objective-C object.

On Deref it then uses the IvarType::NAME string to access the ivar of the containing object.

Note that this is not (currently) allowed by stacked borrows, but due to Object being a zero-sized type such that we don’t have provenance over the ivars anyhow, this should be just as sound as normal instance variable access.

bool handling

This does not perform a conversion step between bool and the Objective-C BOOL; use runtime::Bool when you want your instance variable to be accessible from other Objective-C code.

Safety

This must be used within a type that act as an Objective-C object. In particular, this is never safe to have on the stack by itself.

Additionally, the instance variable described by T must be available on the specific instance, and be of the exact same type. When declaring the object yourself, you can ensure this using ClassBuilder::add_static_ivar.

Finally, two ivars with the same name must not be used on the same object.

Examples

use objc2::declare::{Ivar, IvarType};
use objc2::runtime::Object;

// Declare ivar with given type and name
struct MyCustomIvar;
unsafe impl IvarType for MyCustomIvar {
    type Type = i32;
    const NAME: &'static str = "myCustomIvar";
}

// Custom object
#[repr(C)]
pub struct MyObject {
    inner: Object,
    // SAFETY: The instance variable is used within an object, and it is
    // properly declared below.
    my_ivar: Ivar<MyCustomIvar>,
}

// Declare the class and add the instance variable to it
builder.add_static_ivar::<MyCustomIvar>();

let obj: MyObject;
// You can now access `obj.my_ivar`

See also the declare_ivar.rs example.

Implementations

Get a pointer to the instance variable.

Note that if the ivar has already been initialized, you can simply use the Deref implementation to get a reference.

This is similar to MaybeUninit::as_ptr, see that for usage instructions.

Get a mutable pointer to the instance variable.

This is useful when you want to initialize the ivar inside an init method (where it may otherwise not have been safely initialized yet).

Note that if the ivar has already been initialized, you can simply use the DerefMut implementation to get a mutable reference.

This is similar to MaybeUninit::as_mut_ptr, see that for usage instructions.

Sets the value of the instance variable.

This is useful when you want to initialize the ivar inside an init method (where it may otherwise not have been safely initialized yet).

This is similar to MaybeUninit::write, see that for usage instructions.

Trait Implementations

Converts this type into a mutable reference of the (usually inferred) input type.

Converts this type into a shared reference of the (usually inferred) input type.

Returns the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more

Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to read. Read more

Read all bytes into buf until the delimiter byte or EOF is reached. Read more

Read all bytes until a newline (the 0xA byte) is reached, and append them to the provided buffer. You do not need to clear the buffer before appending. Read more

🔬This is a nightly-only experimental API. (buf_read_has_data_left)

Check if the underlying Read has any data left to be read. Read more

Returns an iterator over the contents of this reader split on the byte byte. Read more

Returns an iterator over the lines of this reader. Read more

Formats the value using the given formatter. Read more

The resulting type after dereferencing.

Dereferences the value.

Mutably dereferences the value.

Formats the value using the given formatter. Read more

Removes and returns an element from the end of the iterator. Read more

Returns the nth element from the end of the iterator. Read more

🔬This is a nightly-only experimental API. (iter_advance_by)

Advances the iterator from the back by n elements. Read more

This is the reverse version of Iterator::try_fold(): it takes elements starting from the back of the iterator. Read more

An iterator method that reduces the iterator’s elements to a single, final value, starting from the back. Read more

Searches for an element of an iterator from the back that satisfies a predicate. Read more

Executes the destructor for this type. Read more

The lower-level source of this error, if any. Read more

👎Deprecated since 1.42.0:

use the Display impl or to_string()

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type based access to context intended for error reports. Read more

Returns the exact remaining length of the iterator. Read more

🔬This is a nightly-only experimental API. (exact_size_is_empty)

Returns true if the iterator is empty. Read more

The type of value produced on completion.

Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more

Feeds this value into the given Hasher. Read more

Feeds a slice of this type into the given Hasher. Read more

Returns the hash value for the values written so far. Read more

Writes some data into this Hasher. Read more

Writes a single u8 into this hasher.

Writes a single u16 into this hasher.

Writes a single u32 into this hasher.

Writes a single u64 into this hasher.

Writes a single u128 into this hasher.

Writes a single usize into this hasher.

Writes a single i8 into this hasher.

Writes a single i16 into this hasher.

Writes a single i32 into this hasher.

Writes a single i64 into this hasher.

Writes a single i128 into this hasher.

Writes a single isize into this hasher.

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras)

Writes a length prefix into this hasher, as part of being prefix-free. Read more

🔬This is a nightly-only experimental API. (hasher_prefixfree_extras)

Writes a single str into this hasher. Read more

The type of the elements being iterated over.

Advances the iterator and returns the next value. Read more

Returns the bounds on the remaining length of the iterator. Read more

Returns the nth element of the iterator. Read more

🔬This is a nightly-only experimental API. (iter_next_chunk)

Advances the iterator and returns an array containing the next N values. Read more

Consumes the iterator, counting the number of iterations and returning it. Read more

Consumes the iterator, returning the last element. Read more

🔬This is a nightly-only experimental API. (iter_advance_by)

Advances the iterator by n elements. Read more

Creates an iterator starting at the same point, but stepping by the given amount at each iteration. Read more

Takes two iterators and creates a new iterator over both in sequence. Read more

‘Zips up’ two iterators into a single iterator of pairs. Read more

🔬This is a nightly-only experimental API. (iter_intersperse)

Creates a new iterator which places an item generated by separator between adjacent items of the original iterator. Read more

Takes a closure and creates an iterator which calls that closure on each element. Read more

Calls a closure on each element of an iterator. Read more

Creates an iterator which uses a closure to determine if an element should be yielded. Read more

Creates an iterator that both filters and maps. Read more

Creates an iterator which gives the current iteration count as well as the next value. Read more

Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. See their documentation for more information. Read more

Creates an iterator that skips elements based on a predicate. Read more

Creates an iterator that yields elements based on a predicate. Read more

Creates an iterator that both yields elements based on a predicate and maps. Read more

Creates an iterator that skips the first n elements. Read more

Creates an iterator that yields the first n elements, or fewer if the underlying iterator ends sooner. Read more

An iterator adapter similar to fold that holds internal state and produces a new iterator. Read more

Creates an iterator that works like map, but flattens nested structure. Read more

Creates an iterator which ends after the first None. Read more

Does something with each element of an iterator, passing the value on. Read more

Borrows an iterator, rather than consuming it. Read more

Transforms an iterator into a collection. Read more

🔬This is a nightly-only experimental API. (iter_collect_into)

Collects all the items from an iterator into a collection. Read more

Consumes an iterator, creating two collections from it. Read more

🔬This is a nightly-only experimental API. (iter_is_partitioned)

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return true precede all those that return false. Read more

An iterator method that applies a function as long as it returns successfully, producing a single, final value. Read more

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error. Read more

Folds every element into an accumulator by applying an operation, returning the final result. Read more

Reduces the elements to a single one, by repeatedly applying a reducing operation. Read more

🔬This is a nightly-only experimental API. (iterator_try_reduce)

Reduces the elements to a single one by repeatedly applying a reducing operation. If the closure returns a failure, the failure is propagated back to the caller immediately. Read more

Tests if every element of the iterator matches a predicate. Read more

Tests if any element of the iterator matches a predicate. Read more

Searches for an element of an iterator that satisfies a predicate. Read more

Applies function to the elements of iterator and returns the first non-none result. Read more

🔬This is a nightly-only experimental API. (try_find)

Applies function to the elements of iterator and returns the first true result or the first error. Read more

Searches for an element in an iterator, returning its index. Read more

Returns the element that gives the maximum value from the specified function. Read more

Returns the element that gives the maximum value with respect to the specified comparison function. Read more

Returns the element that gives the minimum value from the specified function. Read more

Returns the element that gives the minimum value with respect to the specified comparison function. Read more

Converts an iterator of pairs into a pair of containers. Read more

Creates an iterator which copies all of its elements. Read more

Creates an iterator which clones all of its elements. Read more

🔬This is a nightly-only experimental API. (iter_array_chunks)

Returns an iterator over N elements of the iterator at a time. Read more

Sums the elements of an iterator. Read more

Iterates over the entire iterator, multiplying all the elements Read more

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function. Read more

Lexicographically compares the elements of this Iterator with those of another. Read more

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function. Read more

Determines if the elements of this Iterator are equal to those of another. Read more

🔬This is a nightly-only experimental API. (iter_order_by)

Determines if the elements of this Iterator are equal to those of another with respect to the specified equality function. Read more

Determines if the elements of this Iterator are unequal to those of another. Read more

Determines if the elements of this Iterator are lexicographically less than those of another. Read more

Determines if the elements of this Iterator are lexicographically less or equal to those of another. Read more

Determines if the elements of this Iterator are lexicographically greater than those of another. Read more

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another. Read more

🔬This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this iterator are sorted using the given comparator function. Read more

🔬This is a nightly-only experimental API. (is_sorted)

Checks if the elements of this iterator are sorted using the given key extraction function. Read more

This method returns an Ordering between self and other. Read more

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

Restrict a value to a certain interval. Read more

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more

This method returns an ordering between self and other values if one exists. Read more

This method tests less than (for self and other) and is used by the < operator. Read more

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

This method tests greater than (for self and other) and is used by the > operator. Read more

Format as a pointer to the instance variable.

Formats the value using the given formatter.

Pull some bytes from this source into the specified buffer, returning how many bytes were read. Read more

Like read, except that it reads into a slice of buffers. Read more

Read all bytes until EOF in this source, placing them into buf. Read more

Read all bytes until EOF in this source, appending them to buf. Read more

Read the exact number of bytes required to fill buf. Read more

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Reader has an efficient read_vectored implementation. Read more

🔬This is a nightly-only experimental API. (read_buf)

Pull some bytes from this source into the specified buffer. Read more

🔬This is a nightly-only experimental API. (read_buf)

Read the exact number of bytes required to fill cursor. Read more

Creates a “by reference” adaptor for this instance of Read. Read more

Transforms this Read instance to an Iterator over its bytes. Read more

Creates an adapter which will chain this stream with another. Read more

Creates an adapter which will read at most limit bytes from it. Read more

Seek to an offset, in bytes, in a stream. Read more

Returns the current seek position from the start of the stream. Read more

Rewind to the beginning of a stream. Read more

🔬This is a nightly-only experimental API. (seek_stream_len)

Returns the length of this stream (in bytes). Read more

Write a buffer into this writer, returning how many bytes were written. Read more

Like write, except that it writes from a slice of buffers. Read more

Flush this output stream, ensuring that all intermediately buffered contents reach their destination. Read more

Attempts to write an entire buffer into this writer. Read more

Writes a formatted string into this writer, returning any error encountered. Read more

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation. Read more

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer. Read more

Creates a “by reference” adapter for this instance of Write. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The output that the future will produce on completion.

Which kind of future are we turning this into?

Creates a future from a value. Read more

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Creates an iterator from a value. Read more

🔬This is a nightly-only experimental API. (provide_any)

Data providers should implement this method to provide all values they are able to provide by using demand. Read more

Converts the given value to a String. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.