Struct CIQRCodeDescriptor

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

Available on crate feature CIBarcodeDescriptor only.

Expand description

CIQRCodeDescriptor is a concrete subclass of CIBarcodeDescriptor that defines an abstract representation of a QR code symbol.

Implementations§

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impl CIQRCodeDescriptor

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

The error-corrected codewords that comprise the QR code symbol.

QR Codes are formally specified in ISO/IEC 18004:2006(E). Section 6.4.10 “Bitstream to codeword conversion” specifies the set of 8-bit codewords in the symbol immediately prior to splitting the message into blocks and applying error correction.

During decode, error correction is applied and if successful, the message is re-ordered to the state immediately following “Bitstream to codeword coversion.” The errorCorrectedPayload corresponds to this sequence of 8-bit codewords.

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pub unsafe fn symbolVersion(&self) -> NSInteger

The version property corresponds to the size of the QR Code.

QR Codes are square. ISO/IEC 18004 defines versions from 1 to 40, where a higher symbol version indicates a larger data carrying capacity. This field is required in order to properly interpret the error corrected payload.

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pub unsafe fn maskPattern(&self) -> u8

The data mask pattern for the QR code symbol.

QR Codes support eight data mask patterns, which are used to avoid large black or large white areas inside the symbol body. Valid values range from 0 to 7.

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pub unsafe fn errorCorrectionLevel(&self) -> CIQRCodeErrorCorrectionLevel

The error correction level of the QR code.

QR Codes support four levels of Reed-Solomon error correction, in increasing error correction capability: L, M, Q, and H.

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pub unsafe fn initWithPayload_symbolVersion_maskPattern_errorCorrectionLevel( this: Allocated<Self>, error_corrected_payload: &NSData, symbol_version: NSInteger, mask_pattern: u8, error_correction_level: CIQRCodeErrorCorrectionLevel, ) -> Option<Retained<Self>>

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pub unsafe fn descriptorWithPayload_symbolVersion_maskPattern_errorCorrectionLevel( error_corrected_payload: &NSData, symbol_version: NSInteger, mask_pattern: u8, error_correction_level: CIQRCodeErrorCorrectionLevel, ) -> Option<Retained<Self>>

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impl CIQRCodeDescriptor

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.

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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`
    }
}