Struct CIAztecCodeDescriptor

Source

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

Available on crate feature CIBarcodeDescriptor only.

Expand description

CIAztecCodeDescriptor is a concrete subclass of CIBarcodeDescriptor that defines an abstract representation of an Aztec Code symbol.

CIAztecCodeDescriptor may not be instantiated directly.

Implementations§

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impl CIAztecCodeDescriptor

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

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

Aztec Codes are formally specified in ISO/IEC 24778:2008(E).

The error corrected payload consists of the 6-, 8-, 10-, or 12-bit message codewords produced at the end of the step described in section 7.3.1.2 “Formation of data codewords”, which exists immediately prior to adding error correction. These codewords have dummy bits inserted to ensure that an entire codeword isn’t all 0’s or all 1’s. Clients will need to remove these extra bits as part of interpreting the payload.

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pub unsafe fn isCompact(&self) -> bool

A BOOL indicating whether the symbol is compact.

Compact Aztec symbols use one-fewer ring in the central finder pattern than full-range Aztec symbols of the same number of data layers.

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pub unsafe fn layerCount(&self) -> NSInteger

The number of data layers in the Aztec code symbol.

Combined with the isCompact property, the number of data layers determines the number of modules in the Aztec Code symbol. Valid values range from 1 to 32. Compact symbols can have up to 4 data layers.

The number of data layers also determines the number of bits in each data codeword of the message carried by the Aztec Code symbol.

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pub unsafe fn dataCodewordCount(&self) -> NSInteger

The number of non-error-correction codewords carried by the Aztec code symbol.

Used to determine the level of error correction in conjunction with the number of data layers. Valid values are 1…2048. Compact symbols can have up to 64 message codewords.

Note that this value can exceed the number of message codewords allowed by the number of data layers in this symbol. In this case, the actual number of message codewords is 1024 fewer than this value and the message payload is to be interpreted in an application-defined manner.

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pub unsafe fn initWithPayload_isCompact_layerCount_dataCodewordCount( this: Allocated<Self>, error_corrected_payload: &NSData, is_compact: bool, layer_count: NSInteger, data_codeword_count: NSInteger, ) -> Option<Retained<Self>>

Source

pub unsafe fn descriptorWithPayload_isCompact_layerCount_dataCodewordCount( error_corrected_payload: &NSData, is_compact: bool, layer_count: NSInteger, data_codeword_count: NSInteger, ) -> Option<Retained<Self>>

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impl CIAztecCodeDescriptor

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());

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`
    }
}