Struct GKState

Source

pub struct GKState { /* private fields */ }

Available on crate feature GKState only.

Expand description

Represents a single state in a state machine. By default, states allow transitions freely to and from the states in the machine.

If a more restricted set of valid transitions are needed in the state machine, you may override isValidNextState: where applicable.

See: GKStateMachine

See: isValidNextState:

Implementations§

Source §

impl GKState

Source

pub unsafe fn stateMachine(&self) -> Option<Retained<GKStateMachine>>

Available on crate feature GKStateMachine only.

The state machine that this state is associated with. This is nil if this state hasn’t been added to a state machine yet.

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pub unsafe fn state() -> Retained<Self>

Creates a new state to be used in a state machine.

See: GKStateMachine

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pub unsafe fn init(this: Allocated<Self>) -> Retained<Self>

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pub unsafe fn isValidNextState(&self, state_class: &AnyClass) -> bool

Returns YES if the given class is a valid next state to enter.

By default GKState will return YES for any class that is subclass of GKState. Override this in a subclass to enforce limited edge traversals in the state machine.

See: GKStateMachine.canEnterState:

See: GKStateMachine.enterState:

Parameter stateClass: the class to be checked

Returns: YES if the class is kind of GKState and the state transition is valid, else NO.

§Safety

state_class probably has further requirements.

Source

pub unsafe fn didEnterWithPreviousState(&self, previous_state: Option<&GKState>)

Called by GKStateMachine when this state is entered.

Parameter previousState: the state that was exited to enter this state. This is nil if this is the state machine’s first entered state.

See: stateMachineWithStates:initialStateClass:

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pub unsafe fn updateWithDeltaTime(&self, seconds: NSTimeInterval)

Called by GKStateMachine when it is updated

Parameter seconds: the time in seconds since the last update

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pub unsafe fn willExitWithNextState(&self, next_state: &GKState)

Called by GKStateMachine when this state is exited

Parameter nextState: the state that is being entered next

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impl GKState

Methods declared on superclass NSObject.

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pub unsafe fn new() -> Retained<Self>

Methods from Deref<Target = NSObject>§

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pub fn doesNotRecognizeSelector(&self, sel: Sel) -> !

Handle messages the object doesn’t recognize.

See Apple’s documentation for details.

Methods from Deref<Target = AnyObject>§

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pub fn class(&self) -> &'static AnyClass

Dynamically find the class of this object.

§Panics

May panic if the object is invalid (which may be the case for objects returned from unavailable init/new methods).

§Example

Check that an instance of NSObject has the precise class NSObject.

use objc2::ClassType;
use objc2::runtime::NSObject;

let obj = NSObject::new();
assert_eq!(obj.class(), NSObject::class());

Source

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

👎Deprecated: this is difficult to use correctly, use Ivar::load instead.

Use Ivar::load instead.

§Safety

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

See Ivar::load_ptr for details surrounding this.

Source

pub fn downcast_ref<T>(&self) -> Option<&T>
where T: DowncastTarget,

Attempt to downcast the object to a class of type T.

This is the reference-variant. Use Retained::downcast if you want to convert a retained object to another type.

§Mutable classes

Some classes have immutable and mutable variants, such as NSString and NSMutableString.

When some Objective-C API signature says it gives you an immutable class, it generally expects you to not mutate that, even though it may technically be mutable “under the hood”.

So using this method to convert a NSString to a NSMutableString, while not unsound, is generally frowned upon unless you created the string yourself, or the API explicitly documents the string to be mutable.

See Apple’s documentation on mutability and on isKindOfClass: for more details.

§Generic classes

Objective-C generics are called “lightweight generics”, and that’s because they aren’t exposed in the runtime. This makes it impossible to safely downcast to generic collections, so this is disallowed by this method.

You can, however, safely downcast to generic collections where all the type-parameters are AnyObject.

§Panics

This works internally by calling isKindOfClass:. That means that the object must have the instance method of that name, and an exception will be thrown (if CoreFoundation is linked) or the process will abort if that is not the case. In the vast majority of cases, you don’t need to worry about this, since both root objects NSObject and NSProxy implement this method.

§Examples

Cast an NSString back and forth from NSObject.

use objc2::rc::Retained;
use objc2_foundation::{NSObject, NSString};

let obj: Retained<NSObject> = NSString::new().into_super();
let string = obj.downcast_ref::<NSString>().unwrap();
// Or with `downcast`, if we do not need the object afterwards
let string = obj.downcast::<NSString>().unwrap();

Try (and fail) to cast an NSObject to an NSString.

use objc2_foundation::{NSObject, NSString};

let obj = NSObject::new();
assert!(obj.downcast_ref::<NSString>().is_none());

Try to cast to an array of strings.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);
// This is invalid and doesn't type check.
let arr = arr.downcast_ref::<NSArray<NSString>>();

This fails to compile, since it would require enumerating over the array to ensure that each element is of the desired type, which is a performance pitfall.

Downcast when processing each element instead.

use objc2_foundation::{NSArray, NSObject, NSString};

let arr = NSArray::from_retained_slice(&[NSObject::new()]);

for elem in arr {
    if let Some(data) = elem.downcast_ref::<NSString>() {
        // handle `data`
    }
}