I'm trying to convert some of my Obj-C class to Swift. And some other Obj-C classes still using enum in that converted class. I searched In the Pre-Release Docs and couldn't find it or maybe I missed it. Is there a way to use Swift enum in Obj-C Class? Or a link to the doc of this issue?
This is how I declared my enum in my old Obj-C code and new Swift code.
my old Obj-C Code:
typedef NS_ENUM(NSInteger, SomeEnum)
{
SomeEnumA,
SomeEnumB,
SomeEnumC
};
#interface SomeClass : NSObject
...
#end
my new Swift Code:
enum SomeEnum: NSInteger
{
case A
case B
case C
};
class SomeClass: NSObject
{
...
}
Update: From the answers. It can't be done in Swift older version than 1.2. But according to this official Swift Blog. In Swift 1.2 that released along with XCode 6.3, You can use Swift Enum in Objective-C by adding #objc in front of enum
As of Swift version 1.2 (Xcode 6.3) you can. Simply prefix the enum declaration with #objc
#objc enum Bear: Int {
case Black, Grizzly, Polar
}
Shamelessly taken from the Swift Blog
Note: This would not work for String enums or enums with associated values. Your enum will need to be Int-bound
In Objective-C this would look like
Bear type = BearBlack;
switch (type) {
case BearBlack:
case BearGrizzly:
case BearPolar:
[self runLikeHell];
}
To expand on the selected answer...
It is possible to share Swift style enums between Swift and Objective-C using NS_ENUM().
They just need to be defined in an Objective-C context using NS_ENUM() and they are made available using Swift dot notation.
From the Using Swift with Cocoa and Objective-C
Swift imports as a Swift enumeration any C-style enumeration marked with the NS_ENUM macro. This means that the prefixes to enumeration value names are truncated when they are imported into Swift, whether they’re defined in system frameworks or in custom code.
Objective-C
typedef NS_ENUM(NSInteger, UITableViewCellStyle) {
UITableViewCellStyleDefault,
UITableViewCellStyleValue1,
UITableViewCellStyleValue2,
UITableViewCellStyleSubtitle
};
Swift
let cellStyle: UITableViewCellStyle = .Default
From the Using Swift with Cocoa and Objective-C guide:
A Swift class or protocol must be marked with the #objc attribute to
be accessible and usable in Objective-C. [...]
You’ll have access to anything within a class or protocol that’s
marked with the #objc attribute as long as it’s compatible with
Objective-C. This excludes Swift-only features such as those listed
here:
Generics Tuples / Enumerations defined in Swift / Structures defined in
Swift / Top-level functions defined in Swift / Global variables defined in
Swift / Typealiases defined in Swift / Swift-style variadics / Nested types /
Curried functions
So, no, you can't use a Swift enum in an Objective-C class.
Swift 4.1, Xcode 9.4.1:
1) Swift enum must be prefixed with #objc and be Int type:
// in .swift file:
#objc enum CalendarPermission: Int {
case authorized
case denied
case restricted
case undetermined
}
2) Objective-C name is enum name + case name, eg CalendarPermissionAuthorized:
// in .m file:
// point to something that returns the enum type (`CalendarPermission` here)
CalendarPermission calPermission = ...;
// use the enum values with their adjusted names
switch (calPermission) {
case CalendarPermissionAuthorized:
{
// code here
break;
}
case CalendarPermissionDenied:
case CalendarPermissionRestricted:
{
// code here
break;
}
case CalendarPermissionUndetermined:
{
// code here
break;
}
}
And, of course, remember to import your Swift bridging header as the last item in the Objective-C file's import list:
#import "MyAppViewController.h"
#import "MyApp-Swift.h"
If you prefer to keep ObjC codes as-they-are, you could add a helper header file in your project:
Swift2Objc_Helper.h
in the header file add this enum type:
typedef NS_ENUM(NSInteger, SomeEnum4ObjC)
{
SomeEnumA,
SomeEnumB
};
There may be another place in your .m file to make a change: to include the hidden header file:
#import "[YourProjectName]-Swift.h"
replace [YourProjectName] with your project name. This header file expose all Swift defined #objc classes, enums to ObjC.
You may get a warning message about implicit conversion from enumeration type... It is OK.
By the way, you could use this header helper file to keep some ObjC codes such as #define constants.
If you (like me) really want to make use of String enums, you could make a specialized interface for objective-c. For example:
enum Icon: String {
case HelpIcon
case StarIcon
...
}
// Make use of string enum when available:
public func addIcon(icon: Icon) {
...
}
// Fall back on strings when string enum not available (objective-c):
public func addIcon(iconName:String) {
addIcon(Icon(rawValue: iconName))
}
Of course, this will not give you the convenience of auto-complete (unless you define additional constants in the objective-c environment).
After researching this, I kept finding only partial answers, so I created an entire example of a Swift App bridged to Objective C that has Swift enums used by Objective C code and Objective C enums used by Swift code. It is a simple Xcode project that you can run and experiment with. It was written using Xcode 10.3 with Swift 5.0
Example Project
In case you are trying to observe an enum which looks like this:
enum EnumName: String {
case one = "One"
case two = "Two"
}
this workaround helped me.
Observable Class:
create #objc dynamic var observable: String?
create your enum instance like this:
private var _enumName: EnumName? {
didSet {
observable = _enumName!.rawValue
}
}
Observer Class:
create private var _enumName: EnumName?
create private let _instance = ObservableClass()
create
private var _enumObserver: NSKeyValueObservation = _instance.observe(\.observable, options: .new, changeHandler: { [weak self] (_, value) in
guard let newValue = value.newValue else { return }
self?._enumName = EnumName(rawValue: period)!
})
Than's it. Now each time you change the _enumName in the observable class, an appropriate instance on the observer class will be immediately updated as well.
This is of course an oversimplified implementation, but it should give you an idea of how to observe KVO-incompatible properties.
this might help a little more
Problem statement :- I have enum in swift class, which I am accessing form other swift classes, and Now I need to access it form my one of the objective C class.
Before accessing it from objective-c class :-
enum NTCType {
case RETRYNOW
case RETRYAFTER
}
var viewType: NTCType?
Changes for accessing it from objective c class
#objc enum NTCType :Int {
case RETRYNOW
case RETRYAFTER
}
and add a function to pass it on the value
#objc func setNtc(view:NTCType) {
self.viewType = view; // assign value to the variable
}
Related
I have a situation. I would appreciated if anyone has a solution for this
I have an objC enum say Abc
I declare this in a swift class, say, MySwiftClass.swift as var abc : Abc!
I have created an instance of MySwiftClass (mySwiftClass) in another ObjC class (myObjC.m file)
In myObjC.m, I’m trying to access enum Abc as mySwiftClass.abc.
This is throwing an error - “Property ‘abc’ not found on object of type MySwiftClass *”.
Basically the enum is not added as property in the “ProjectName-Swift.h” file.
What I believe is happening is that when I’m declaring the ObjC enum in Swift class, it is getting converted to a swift enum and hence I’m not able to access it in ObjC file.
Note: Marking the Swift class as #objc did not work.
Numeric Swift optionals cannot be represented in Objective-C, and thus will not be exposed to Objective-C. Declare abc to not be optional and it should be available from Objective-C.
Consider this Objective-C enumeration:
typedef NS_ENUM(NSInteger, Foo) {
FooBar,
FooBaz,
FooQux
};
Then consider this Swift 3 class:
class SomeObject: NSObject {
var foo1: Foo = .bar // this is exposed to Objective-C
var foo2: Foo! = .bar // this is not
}
The non-optional, foo1, will be exposed to Objective-C, whereas the optional, foo2, will not.
I am writing an OS X/iOS framework in Objective-C, and I would like for the framework to be useful for developers using either Objective-C or Swift.
In normal Objective-C enums are defined like this (this example is taken directly from Apple's own UIView class reference).
typedef enum {
UIViewAnimationCurveEaseInOut,
UIViewAnimationCurveEaseIn,
UIViewAnimationCurveEaseOut,
UIViewAnimationCurveLinear
} UIViewAnimationCurve;
To make this enum Swift-friendly, my understanding is that it should be declared like this.
typedef NS_ENUM(NSInteger, UIViewAnimationCurve) {
UIViewAnimationCurve_EaseInOut,
UIViewAnimationCurve_EaseIn,
UIViewAnimationCurve_EaseOut,
UIViewAnimationCurve_Linear
};
This allows the enum to be accessed in the style of let curve: UIViewAnimationCurve = .EaseInOut from Swift.
My problem is that the NS_ENUM and underscore method produces strangely named enums when used from Objective-C. The NS_ENUM method allows dot notation to be used from Swift, but it also means that any ObjC code will need to use an underscore in the enumerated name, which is undesirable.
How can I allow dot notation for Swift while still preserving Objective-C style naming conventions for within ObjC code?
You simply follow the usual convention – no underscoring is necessary. Swift compiler is smart enough to just cut the common prefix out (the part that matches the enum type name). You do have to use an NS_ENUM for the enum to be made visible to Swift, but it's good practice anyway.
Case in point, for instance UIViewAnimationCurve is defined in an Objective-C header in just the form you describe in your first code example and works just fine in Swift:
If you define it like this:
typedef long TrafficLightColor NS_TYPED_ENUM;
TrafficLightColor const TrafficLightColorRed;
TrafficLightColor const TrafficLightColorYellow;
TrafficLightColor const TrafficLightColorGreen;
if get compiled to swift like this:
struct TrafficLightColor: RawRepresentable, Equatable, Hashable {
typealias RawValue = Int
init(rawValue: RawValue)
var rawValue: RawValue { get }
static var red: TrafficLightColor { get }
static var yellow: TrafficLightColor { get }
static var green: TrafficLightColor { get }
}
Looks like what you need, anyway take a look at: https://itunes.apple.com/us/book/using-swift-with-cocoa-and-objective-c-swift-4-1-beta/id1002624212?mt=11
Im in a situation where I need to use Objective-C category to extend a Swift class. I've done something as follows:
In "SomeClass.swift":
class SomeClass: NSObject {
}
In "SomeClass+Extension.h":
#import "Project-Swift.h"
#interface SomeClass (Extension)
-(void)someMethod();
#end
This has worked well. And if I try to use the SomeClass extension in my Objective C code, it is fine.
The problem is, if I want to use someMethod() in a another Swift class, I will need to put the SomeClass+Extension.h file into my ObjC-BridgingHeader.h file.
But doing this will cause a circular dependency, because SomeClass+Extension.h also imports Project-Swift.h.
Does anyone have a good way to get around this?
Please note that simply forward declaring the class in the category header will not work, as categories cannot use forward declarations for it's own implementation as so:
#class SomeClass without importing Project-Swift.h will give a compile error.
The Bad
i too have been fighting this issue a bunch. unfortunately the documentation pretty explicitly states that this pattern is not allowed:
To avoid cyclical references, don’t import Swift code into an
Objective-C header (.h) file. Instead, you can forward declare a Swift
class or protocol to reference it in an Objective-C interface.
Forward declarations of Swift classes and protocols can only be used
as types for method and property declarations.
also throughout the the linked page you will notice it keeps mentioning to import the generated header specifically into the .m file:
To import Swift code into Objective-C from the same target
Import the Swift code from that target into any Objective-C .m file
within that target
The Good
one solution that may work for you is to create a swift extension that redefines each method you need in the category. it is fragile and ugly, but arguably the cleanest solution.
/**
Add category methods from objc here (since circular references prohibit the ObjC extension file)
*/
extension SomeClass {
#nonobjc func someMethod() {
self.performSelector(Selector("someMethod"))
}
}
adding the #noobjc to the front allows the
same method signature to be used w/o overriding the ObjC implementation
now the import "SomeClass+Extension.h" from the bridging
header can be removed
if support for more than two input params is needed, or tighter type coupling is desired i would recommend using the runtime to call the underlying function. a great description is here.
From the Interoperability guide, we cannot directly access the subclassed / categorized / extensioned Objc-objects for the .swift [SomeClass] class.
But as a turn-around, we can do this:
For Variables , we can do this:
extension Class {
private struct AssociatedKeys {
static var DescriptiveName = "sh_DescriptiveName"
}
var descriptiveName: String? {
get {
return objc_getAssociatedObject(self, &AssociatedKeys.DescriptiveName) as? String
}
set {
if let newValue = newValue {
objc_setAssociatedObject(
self,
&AssociatedKeys.DescriptiveName,
newValue as NSString?,
.OBJC_ASSOCIATION_RETAIN_NONATOMIC
)
}
}
}
}
For Methods, we can use method_swizzling which is not recommended.
As one simple solution, you can move the extension to your Swift code. Then you won't have any dependency problems.
I want to wrap a C-library (handling some NumberTheory related items, which I wrote some 20 years ago in C) into Swift. I started writing an Objective-C wrapper for this C-library, end then wrote a Swift derived class from the Objective-C wrapper.
Since Objective-C doesn't allow me to write overloaded methods/operators, I want to accomplish this in Swift. The C-library in question has API-calls starting with 'numthe' and a libnumthe.a and a "numthe.h" include file. The Objective-C wrapper/class is called NumTheObjC and the Swift class NumThe
Currently I've the following code for the NumTheObjC.h file:
#import <Foundation/Foundation.h>
#import <stdio.h>
#import "numthe.h"
#interface NumTheObjC : NSObject
{
numthe_prime nPrime; // Holds a numthe_prime number type instance.
numthe_perfect nPerfect; // Holds a numthe_perfect number type instance.
//... more numthe types/structure instances here.
}
-(id)init; // Default initializer
-(id)init:(NSString *)str; // Initialize from string-value.
-(void)add:(NumTheObjC *)op; // a += b
+(NumTheObjC *)add:(NumTheObjC *)left right:(NumTheObjC *)right; // x = a + b
-(void)setFromInt:(signed int)nrInt; // Initialize/set from int.
-(void)setFromLong:(signed long)nrLong; // Initialize/set from long.
-(void)setFromUInt:(unsigned int)nrUInt; // Initialize/set from uint.
-(void)setFromULong:(unsigned long)nrULong; // Initialize/set from ulong.
#end
And for the Swift wrapper I came up with the NumThe.swift file:
class NumThe : NumTheObjC {
init(nr: Int) {
super.init()
setFromInt(nr)
}
init(nr: UInt) {
super.init()
setFromUInt(nr)
}
init(strNr: String) {
super.init(strNr)
}
//... more overloaded 'constructors/initializers here ...
}
//-- Overloaded operator a + b
func + (inout left: NumThe, right: NumThe) -> NumTheObjC {
return NumTheObjC.add(left, right: right)
}
//-- Overloaded operator +=
func += (inout left: NumTheObjC, right: NumThe) {
return left.add(right)
}
Still some thoughts and questions remain, viz.:
1. I'm wondering if the above is the best approach to accomplish my goal.
2. Should the signature of all methods use NumTheObjC parameter-types instead of NumThe?
3. I can't seem to figure out how to let the above overloaded operator for 'a + b' return a NumThe instance instead of the NumTheObjC-instance.
4. Is there a more efficient approach in using C++ like templates/types to get all kinds of overloaded methods/operators?
Thanks in advance for any suggestions/tips!
1. I'm wondering if the above is the best approach to accomplish my goal.
You can need a new subclass NumThe. You can add new init() via extension of NumTheObjC. See this Apple doc for more info
2. Should the signature of all methods use NumTheObjC parameter-types instead of NumThe?
If you use extension then you do not need to change your parameter types
3. I can't seem to figure out how to let the above overloaded operator for 'a + b' return a NumThe instance instead of the NumTheObjC-instance.
Solution for point 1 ('extension') should resolve this too
4. Is there a more efficient approach in using C++ like templates/types to get all kinds of overloaded methods/operators?
I don't think it is possible. Again check out this Apple doc, the Preprocessor Directives section.
I am migrating a UIViewController class to train a bit with Swift. I am successfully using Objective-C code via the bridging header but I have the need of importing a constants file that contains #define directives.
I have seen in Using Swift with Cocoa and Objective-C (Simple macros) the following:
Simple Macros
Where you typically used the #define directive to define a primitive constant in C and Objective-C, in Swift you use a global constant instead. For example, the constant definition #define FADE_ANIMATION_DURATION 0.35 can be better expressed in Swift with let FADE_ANIMATION_DURATION = 0.35. Because simple constant-like macros map directly to Swift global variables, the compiler automatically imports simple macros defined in C and Objective-C source files.
So, it seems it's possible. I have imported the file containing my constants into the bridging header, but I have no visibility from my .swift file, cannot be resolved.
What should I do to make my constants visible to Swift?
UPDATE:
It seems working with NSString constants, but not with booleans:
#define kSTRING_CONSTANT #"a_string_constant" // resolved from swift
#define kBOOL_CONSTANT YES // unresolved from swift
At the moment, some #defines are converted and some aren't. More specifically:
#define A 1
...becomes:
var A: CInt { get }
Or:
#define B #"b"
...becomes:
var B: String { get }
Unfortunately, YES and NO aren't recognized and converted on the fly by the Swift compiler.
I suggest you convert your #defines to actual constants, which is better than #defines anyway.
.h:
extern NSString* const kSTRING_CONSTANT;
extern const BOOL kBOOL_CONSTANT;
.m
NSString* const kSTRING_CONSTANT = #"a_string_constant";
const BOOL kBOOL_CONSTANT = YES;
And then Swift will see:
var kSTRING_CONSTANT: NSString!
var kBOOL_CONSTANT: ObjCBool
Another option would be to change your BOOL defines to
#define kBOOL_CONSTANT 1
Faster. But not as good as actual constants.
Just a quick clarification on a few things from above.
Swift Constant are expressed using the keywordlet
For Example:
let kStringConstant:String = "a_string_constant"
Also, only in a protocol definition can you use { get }, example:
protocol MyExampleProtocol {
var B:String { get }
}
In swift you can declare an enum, variable or function outside of any class or function and it will be available in all your classes (globally)(without the need to import a specific file).
import Foundation
import MapKit
let kStringConstant:String = "monitoredRegions"
class UserLocationData : NSObject {
class func getAllMonitoredRegions()->[String]{
defaults.dictionaryForKey(kStringConstant)
}
simple swift language don't need an macros
all #define directives.
will be let
and complex macros should convert to be func
The alternative for macro can be global variable . We can declare global variable outside the class and access those without using class. Please find example below
import Foundation
let BASE_URL = "www.google.com"
class test {
}