Struct NSFileProviderItemVersion

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#[repr(C)]
pub struct NSFileProviderItemVersion { /* private fields */ }

Available on crate feature NSFileProviderItem only.

Expand description

Apple’s documentation

Implementations§

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impl NSFileProviderItemVersion

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pub unsafe fn beforeFirstSyncComponent() -> Retained<NSData>

Version component exposed by the system to denote a state that predates a version returned by the provider.

In case an item was created by calling createItemBasedOnTemplate and the item returned by the provider in the completion handler of that call didn’t match the item template passed by the system, the system will try to apply the changes asked by the provider to the disk. However, the system may detect conflicts when applying those content back to the disk, which will cause the system to send the new disk version to the extension, by calling modifyItem or deleteItemWithIdentifier with a baseVersion that represents the item as passed in the template of the createItemBasedOnTemplate call.

This constant is used by the system to represent that specific version that was communicated by the system to the extension but does not have a corresponding version assigned by the extension.

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pub unsafe fn initWithContentVersion_metadataVersion( this: Allocated<Self>, content_version: &NSData, metadata_version: &NSData, ) -> Retained<Self>

Items versions have two distinct components, one for the file contents and one for metadata.

Components are limited to 128 bytes in size.

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pub unsafe fn contentVersion(&self) -> Retained<NSData>

Version data for the content of the file.

This property is used by the system for two purposes: if the contentVersion changes,

the system assumes that the contents have changed and will trigger a redownload if necessary. The exception to this is the case where the extension accepts a content sent by the system when replying to a createItemBasedOnTemplate or modifyItem call with shouldFetchContent set to NO.
the thumbnail cache is invalidated

Note that the resource fork of the file is considered content, so this version data should change when either the data fork or the resource fork changes.

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pub unsafe fn metadataVersion(&self) -> Retained<NSData>

Version data for the metadata of the item, i.e everything but the data fork and the resource fork.

The system will store this version, but otherwise ignore it:

metadata changes on an item will be applied even if the metadataVersion remains unchanged
if the metadata version changes without any corresponding observable changes in the metadata returned to the system, the system will simply store the updated metadata version (to return it as the base version of a possible future change request).

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impl NSFileProviderItemVersion

Methods declared on superclass NSObject.

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

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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());

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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`
    }
}