I have a Framework with has one Objective-C class with one designated initializer which takes two NSArrays. Inside the Framework, I have defined a Swift extension which provides an extra initializer which takes an array of tuples instead of the two arrays.
When importing the Framework eternally, is it possible to hide the original Objective-C initializer from Swift (so only the initializer taking the array of tuples can be used) but keep it available when using the Framework from Objective-C code?
Answer by #mattt:
Use the NS_SWIFT_UNAVAILABLE macro (available only on Xcode 7 and up).
You could:
YourApp-Brindging-Header.h
#define __BRIDGING__
#import "YourObjCObject.h"
#undef __BRIDGING__
YourObjCObject.h
#import <Foundation/Foundation.h>
#interface YourObjCObject : NSObject
#property (assign, nonatomic) NSInteger count;
- (instancetype)initWithArray:(NSArray *)ary1 Array2:(NSArray *)ary2 NS_DESIGNATED_INITIALIZER
#ifdef __BRIDGING__
NS_UNAVAILABLE
#endif
;
#end
Related
I got a Swift Project with an Objective-C library linked via CocoaPods. It works fine, I can call all methods etc. Also my Bridging-Header is existing and working.
But I got a problem with some properties of my Objective-C classes.
Here is my class:
#import <Foundation/Foundation.h>
#import "OAIObject.h"
#import "OAILayerTreeGroupAllOf.h"
#import "OAILayerTreeItem.h"
#protocol OAILayerTreeGroupAllOf;
#class OAILayerTreeGroupAllOf;
#protocol OAILayerTreeItem;
#class OAILayerTreeItem;
#protocol OAILayerTreeGroup
#end
#interface OAILayerTreeGroup : OAILayerTreeItem
#property(nonatomic) NSArray<OAILayerTreeItem>* children;
#end
I can create this object from Swift code.
But if I try to access the children I get the type "Any", so I can't access the property children.
Is there a way to access the property type of my Objective-C class?
I suspect the problem is that your Objective-C generics declaration does not contain a *.
Can you try to change your property declaration to
#property(nonatomic) NSArray<OAILayerTreeItem *> *children;
Your NSArray instance contains objects that are of type OAILayerTreeItem, that's why you need the *.
Please note that I was unable to try this.
I have an Objective-C header that has to be used by a Swift class. However, this header has to use the Swift.h file for an enum declared in a Swift file. In other words, the setup is as follows:
MPViewController.h
#import "MyProject-Swift.h"
#interface MPViewController: UIViewController
#property (nonatomic, assign) MPSomeEnum theEnum;
...
#end
MyProject-Bridging-Header.h
...
#import "MPViewController.h"
...
SomeEnum.swift
#objc enum MPSomeEnum: Int {
...
}
When compiling the code, I get three errors:
'MyProject-Swift.h' file not found
Failed to emit precompiled header [Xcode DerivedData folder]/[...]/MyProject-Bridging-Header-swift_[...].pch for bridging header [Project folder]/MyProject-Bridging-Header.h
Unknown type name 'MPSomeEnum'
Am I correct to assume that this stems from the circular reference between MyProject-Swift.h and the bridging header MyProject-Bridging-Header.h? From looking at a similar question one solution is to use forward declaration. However, it doesn't seem possible to forward declare an enum, so perhaps the only way to do this is to move the enum definition to an Objective-C file altogether?
TL&DR; As you suspected, you need to either move the enum declaration to Objective-C, or migrate the class to Swift.
Forward declarations of enums is possible in Objective-C:
#property SomeEnum someProperty;
- (void)doSomethingWithEnum:(enum SomeEnum)enumValue;
However correct Cocoa enums are typedefs to NSInteger: typedef NS_ENUM(NSInteger, MyEnum), and the enum keyword doesn't hold enough information for how much space to allocate when using it, so you'll get into all kind of compiler error when you want to use declarations like this. Thus an enum declared in Swift is not forward declarable in Objective-C.
Now, if you really want to keep the enum definition in Swift, you could use a workaround, and declare it as NSInteger in Objective-C, while providing a specialized property in Swift:
// NS_REFINED_FOR_SWIFT imports this in Swift as __theEnum
#property(nonatomic, assign) NSInteger theEnum NS_REFINED_FOR_SWIFT;
extension MPViewController {
// we provide a wrapper around the Objective-C property
var theEnum: MPSomeEnum {
// this uses a forced unwrap, beware :)
return MPSomeEnum(rawValue: theEnum)!
}
}
My project currently has a file containing many constants that I use in a variety of places throughout my codebase. I'm writing a class extension in swift and need to access some of these constants.
I have something like this defining my constants in Objective-C:
//
// AppConstants.h
//
#import <Foundation/Foundation.h>
#interface AppConstants : NSObject
extern NSString *const SOME_CONSTANT_IN_APP_CONSTANTS;
#end
I've added my AppConstants.h to the bridging header, but when I try and do:
someDictionary.objectForKey(PROPERTY_CALL_CAMPUS_SECURITY_TITLE)
I get:
Use of unresolved identifier 'PROPERTY_CALL_CAMPUS_SECURITY_TITLE'
Is there a way to access constants defined in Objective-C in my Swift code?
I have an obj-c project to which I successfully added a new Swift class A, which is being used by some existing obj-c class B - the use of the automatically generated "MyProject-Swift.h" header worked as expected.
I also successfully added a new Swift class C that uses some existing obj-c class D - the use of the bridging header also worked as expected.
However, suppose I want to refer from my Swift class C to the existing obj-c class B (which in turn refers to the new Swift class A). In order to do that I need to import "B.h" to the bridging header. However, if I do that I get an error in class B: "'MyProject-Swift.h' file not found" (i.e., the file is no longer generated).
Am I doing something wrong or is this a kind of interaction between Swift and Objective-C that is not allowed? It looks like there is a kind of circular reference that the compiler is unable to solve.
--- EDIT ---
I'll try to make the question clearer by adding some code.
-- PREAMBLE --
I added a new Swift class to an obj-c project:
// SwiftClassA.swift
import Foundation
#objc class SwiftClassA : NSObject {
var myProperty = 0
}
The code compiles correctly and is translated into obj-c stubs in the automatically generated "MyProject-Swift.h" header like so:
// MyProject-Swift.h
...
SWIFT_CLASS("_TtC7MyProject11SwiftClassA")
#interface SwiftClassA : NSObject
#property (nonatomic) NSInteger myProperty;
- (instancetype)init OBJC_DESIGNATED_INITIALIZER;
#end
Now, one obj-c class uses SwiftClassA:
// ObjCClass.h
#import <Foundation/Foundation.h>
#import <MyProject-Swift.h>
#interface ObjCClass : NSObject
#property (nonatomic, strong) SwiftClassA *aProperty;
#property (nonatomic) int *aNumber;
#end
This also works seamlessly.
-- THE QUESTION --
Can I now create a new Swift class that refers to the obj-c class (ObjCClass) that is using the Swift class SwiftClassA?
This is what I can't do.
If I add the new Swift class:
// SwiftClassB.swift
import Foundation
#objc class SwiftClassB : NSObject {
var aPropertyOfClassB = 1
func someFunc() {
var objCObject = ObjCClass()
var theProperty = objCObject.aProperty
print("The property is \(theProperty)")
}
}
this of course won't compile because of "Use of unresolved identifier 'ObjCClass'". So I need to add that to the bridging header file:
// BridgingHeader.h
#ifndef MyProject_BridgingHeader_h
#define MyProject_BridgingHeader_h
...
#import "ObjCClass.h"
#endif
However, if I do that, the ObjCClass.h file won't compile giving a "'MyProject-Swift.h' file not found".
I've read in several places (with no example, though) that this may mean that there is a circular reference and that a forward reference using #class could solve the problem. However, I'm not sure what needs to be forward referenced and where, and all my attempts failed.
I hope the question is no longer confusing now!
This is a typical cyclical referencing problem.
Be careful to read the docs:
To avoid cyclical references, don’t import Swift into an Objective-C header file. Instead, you can forward declare a Swift class to use it in an Objective-C header. Note that you cannot subclass a Swift class in Objective-C.
So, you should use "forward declare" in .h, and #import in .m:
// ObjCClass.h
#import <Foundation/Foundation.h>
#class SwiftClassA;
#interface ObjCClass : NSObject
#property (nonatomic, strong) SwiftClassA *aProperty;
#property (nonatomic) int *aNumber;
#end
// ObjCClass.m
#import "ObjCClass.h"
#import "MyProject-Swift.h"
#implementation ObjCClass
// your code
#end
Recently I used an opaque pointer type in my code. I did this because I wanted to use c++ code in my obj c project without having to change every single file to .mm.
The way I use the c++ code is that I have a opaque pointer to my c++ code as a member of a .mm file. All the c++ is hidden in the implementation file.
In this class that contains my c++ I have a need to import an existing class "MyClass". I can import it fine in the implementation class but if I try to import it in the header I get c++ errors saying " ISO C++ forbids declaration of 'CARingBufferCPPWrapper' with no type".
I "can" just write the method in the .mm file and omit it from the header but I get a warning say that my .mm file may not respond to the method.
A lot of this is quite new to be so my terminology may be a little off. Let me know if I can clarify my question in any way.
TLDR: How can Class X Safely call a method in Class Y without the method being declared in Class Y header?
//My Header
#import <Foundation/Foundation.h>
#import <AudioToolbox/AudioToolbox.h>
#define kBufferLength 5120
//#define "Myclass.h"
typedef struct ringbufferobj * RingBufferOBJ;
RingBufferOBJ newRingBufferOBJ();
#interface CARingBufferCPPWrapper : NSObject {
RingBufferOBJ ringbuffer;
NSThread *producerthread;
int duration;
}
#property (nonatomic, retain) NSThread *producerthread;
#property(nonatomic)int duration;
//-(void)myclassfunction(MyClass *)classref
#end
//My Implementation .mm
#import "CARingBufferCPPWrapper.h"
#import "CARingBuffer.h"
#import <AudioToolbox/AudioToolbox.h>
#import "MyClass.h"
struct ringbufferobj
{
CARingBuffer *ringbuffer;
AudioBufferList *inputbuffer;
Float64 firstInputSampleTime;
Float64 firstOutputSampleTime;
Float64 inToOutSampleTimeOffset;
BOOL producerthreadisrunning;
};
RingBufferOBJ newRingBufferOBJ(){
RingBufferOBJ ringbuffer=(RingBufferOBJ)malloc(sizeof(struct ringbufferobj));
return ringbuffer;
}
#implementation CARingBufferCPPWrapper
#synthesize producerthread;
#synthesize duration;
-(void)myclassfunction(MyClass *)classref
{
}
#end
I'm not quite sure what your question is as I couldn't find anything that actually asks anything. (I even Cmd+F'd for "?"). I'm assuming however, that you're asking what you can do to get rid of that warning?
-If a method is declared above the method it is called it, there should be no warning. ( methods are compiled in order). To get rid of such a warning, you'd have to forward declare the method signature. (This is conventionally in the header, but I don't think there's anything stopping you just doing it at the top of your .m)
-(void) methodA {
..do something
[self methodB]; //Warning here because the compiler has not yet seen methodB
}
-(void) method B {
..[self methodA]; //No warning, compiler knows what methodA is at this point.
}