I've got an Objective C project and I'm trying to use Swift file in it. I've added swift file and Xcode automatically created Bridging Header. So I could create an object of my swift class in obj-c file and access to its properties. But then I added a new string to my swift file. And I can’t access a new-added property from my objective C file. So I think, I have to update or recreate Bridging Header, haven't I? Can anybody help me?
Did you put #objc in front of your class or property? like:
#objc public class myClass {
#objc var str: String = "str"
}
Related
I have created a class in Swift (which I'm learning) that I use to hold certain values as follows:
#objc public class Book: NSObject {
var title: String = ""
var date: Date = Date()
var sku: Float = 0
}
I would now like to store this class in the equivalent of a property that can be accessed by my Objective-C class.
I tried creating a variable in the View Controller where the class is used as follows:
var lastBookViewed = Book()
However, when I try to save the object to the property with the followng code, I get an error:
//create instance of book
let myBook = Book()
//gather information about book
lastBookViewed = myBook //THROWS COMPILER ERROR 'Use of Unresolved Identifier lastBookViewed
Is there a way to do this?
If easier, storing the object to a property in the Objective-C file would work as well but so far I have not been able to get the Objective-C file to recognize the Book class created in Swift although I put #objc before it as recommended.
Edit
When I try to create a property or variable for storing the custom swift object in a different Swift class (the View Controller class) in the same Swift file with the following syntax:
var lastBookViewed: Book
the compiler gives a warning for the VC class "yourVC has no initializers"
Go to your project’s general settings. Select the proper target for your app. Go to “Build Settings” and switch to “All”, instead of “Basic” which is the default. Here search for the “Packaging” section. Turn on “Defines Module”, by changing “No” to “Yes”.
When this is turned on we will now be able to use swift classes inside
of objective-c files.
Before leaving the “Build Settings” look for “Product Module Name” in the “Packaging” section. This will be important so make sure to take note of and copy the “Product Module Name” exactly.
Next go to an objective-c class where you would like to be able to have access to your swift class. In the implementation or .m file of this class import a header like this:
#import "MyProjectModuleName-Swift.h"
Here the file name of the import must be the exact Project Module Name from the build settings. Any objective-c file where you want access to your swift class should include this import.
Now it is worth mentioning one potential issue that may arise when using a swift class. Objective-c cannot read top-level swift classes. So if you go to use a method or variable from your swift class directly it will not be recognized. There are one simple solution to this issue. It’s to make your class public
#objc public class myClass
Suppose I have a connector named Connector.m (written in Objective-C). And I would like to create a new connector written using Swift, named Connector.swift. I would like to access all of the variables and methods from Swift. I have create a bridging-header and write import of the header file of the Connector. But I can't access any of global variables on the Objective-C class.
Connector.m
NSString * const kHTTP_METHOD_GET = #"GET";
Connector.swift
public class Connector: NSObject {
var parentConnector : Connector
override init() {
self.parentConnector = Connector
}
func test() {
print(parentConnector.kHTTP_METHOD_GET) //--> ERROR : Value of type 'Connector' has no member 'kHTTP_METHOD_GET'
}
}
Is it possible to do this? Thanks.
Make sure you have header file like this...
{project-name}-Bridging-Header.h
Add your class file in Bridging-Header.h
#import "Connector.h"
And Put your below code in Connector.h file..Because in Bridging-Header.h will only import header file
NSString * const kHTTP_METHOD_GET = #"GET";
to on top of #interface scope..
Add following line in Connector.h.
extern NSString * const kHTTP_METHOD_GET;
Include Connector.h to your bridging header file.
I believe the methods/variables in Connector.m also need to be public for it to work.
This sounds like a good use-case for the Adapter Pattern. But you should be able to access Objective-C code easily.
Make sure your bridging header file is named like this:
{your-project-name}-Bridging-Header.h
Inside your bridging header add the following:
#import "Connector.m"
Then you have to make sure the compiler knows about your bridging header:
Click your root project > Select your target app > Build Settings
Then scroll down until you see this:
Make sure your bridging header is listed, build and you should have access to your Objective-C code.
I have a swift class defined in a framework that is being used from an obj-c app.
The generated -Swift.h header contains the swift classes marked with #objc but there's one property that makes the compilation fail.
This property is defined like this in swift code :
public var storageClass : StorageProtocol.Type = UserDefaultStorage.self
and so the generated obj-c property looks like this
#property (nonatomic) Class <StorageProtocol> __nonnull storageClass;
But Xcode does not accepts the "StorageProtocol" symbol here, because the forward declaration "#protocol StorageProtocol;" is missing.
If I add a new var defined like this :
public var storage : StorageProtocol? = nil
The forward declaration is added on top of class that define these properties and the -Swift.h compilation succeed.
So it looks like a bug in the -Swift.h generation, but is there another way to force that forward declaration without using a dummy var ?
I did not find any other way than using a dummy var...
When you implement a class MyGreatClass in Swift its fully qualified name will by <MyPackageName>.MyGreatClass. This is different to Objective-C, where the fully qualified name of that same class is MyGreatClass.
Unfortunately this introduces a problem for me. When I am using NSUnarchiver and the archive was written with Objective-C objects I cannot unpack it with Swift-classes(see below for a detailed description).
This means I need to find a way to rename the namespace for my Swift classes. How do I do that?
Any help would be great!
Background: Why can't NSUnarchiver see/load my swift class?
I have implemented a small program to read a file, which was archived with NSArchive.
These are my files:
main.swift:
import Foundation
// parse command line - total path to *.trace file (from Apple's Instruments app)
var traceFilePath = Process.arguments[1]
var traceFile = NSURL(fileURLWithPath: traceFilePath)
var error:NSError?
// check if the file exists
if (traceFile?.checkResourceIsReachableAndReturnError(&error) == false){
// file does not exist or cannot be accessed
println("\(error)")
exit(1)
}
var rawData = NSData(contentsOfURL: traceFile!)
var data = NSUnarchiver(forReadingWithData: rawData!)
var decodedObject: AnyObject? = data?.decodeObject()
XRObjectAllocRun.swift:
import Foundation
class XRObjectAllocRun: NSObject {
// class to be implemented
}
When I now run my application on an Instruments-file I am getting the following error: Terminating app due to uncaught exception 'NSArchiverArchiveInconsistency', reason: '*** class error for 'XRObjectAllocRun': class not loaded'.
This is really strange because when I add the exact same class in an Objective-C file with a bridging header file I have no issues.
trace file reader-Bridging-Header.h: is empty.
XRObjectAllocRun.h:
#import <Foundation/Foundation.h>
#interface XRObjectAllocRun : NSObject
#end
XRObjectAllocRun.m:
#import "XRObjectAllocRun.h"
#implementation XRObjectAllocRun
#end
What am I missing? Why is my Objective-C class found, whereas my Swift class is not?
Swift has no issues for example with var x = XRObjectAllocRun() in main.swift, but yet the NSUnarchiver still complaints about a missing XRObjectAllocRun class when I stay purely within Swift. Is the NSUnarchiver looking in the wrong places - does it for some reason only accept Objective-C classes?
If you want to know what I am trying to do check this stackoverflow question out.
Update
This is what apple writes:
Swift classes are namespaced based on the module they are compiled in, even when used from Objective-C code. Unlike Objective-C, where all classes are part of a global namespace
Further more:
For example, when you create a document–based Mac app, you provide the name of your NSDocument subclass in your app’s Info.plist file. In Swift, you must use the full name of your document subclass, including the module name derived from the name of your app or framework.
Yikes, trying to figure out the mess now...
Try this when you declare your class:
#objc(XRObjectAllocRun) class XRObjectAllocRun: NSObject {
// class to be implemented
}
That will give this class the same name as the archived class, namely XRObjectAllocRun, instead of the namespaced Swift name trace_file_reader.XRObjectAllocRun.
This is always a concern when you're translating from Objective-C to Swift and you've got an existing archive to deal with. See Apple's documentation:
https://developer.apple.com/library/ios/documentation/Swift/Conceptual/BuildingCocoaApps/InteractingWithObjective-CAPIs.html
Note the discussion under "Exposing Swift Interfaces in Objective-C".
I'm attempting to use Swift classes in my Objective-C code, however my Swift classes don't seem to appear in the generated header. As a result, my build fails with "Use of undeclared identifier 'HelloWorld'".
I used the templates to create a project called TestApp.
I have the following Build Settings in my target:
Product Name : TestApp
Product Module Name : TestAppModule
Defines Module : Yes
Apple's documentation says to use #import <TestApp/TestAppModule-Swift.h> but this doesn't work.
Instead, I'm using #import "TestAppModule-Swift.h" in my ".m" file. It seems to find this.
I'm able to navigate to it, and it looks like this...
// Generated by Swift version 1.0 (swift-600.0.34.4.5)
#if defined(__has_include) && __has_include(<swift/objc-prologue.h>)
# include <swift/objc-prologue.h>
#endif
...etc...
but no classes defined in there.
I have a Swift file in the project that looks like this...
class HelloWorld {
func hello() {
println("hello world")
}
}
Why isn't this working using the standard header file location #import <TestApp/TestAppModule-Swift.h>?
How can I get my swift classes in that header file, so I won't get the "undeclared identifier" error?
Here's how I have gotten it to work. You can see a more large-scale answer here.
Change this:
class HelloWorld {
func hello() {
println("hello world")
}
}
To:
#objc class HelloWorld {
class func newInstance() -> HelloWorld {
return HelloWorld()
}
func hello() {
println("hello world")
}
}
Then, In your ObjC file:
#import "TestApp-Swift.h"
And call like this:
HelloWorld * helloWorld = [HelloWorld newInstance];
[helloWorld hello];
tl;dr Ensure you have a bridging header if you're doing any cross-calling between Objective-C and Swift.
I had the exact same problem: I could see the -Swift.h file in DerivedData but it made no mention of my Swift classes. I was importing the header file correctly, the Defines Module setting was YES, and the Product Module Name was correct. I tried deleting and re-adding the Swift files, clean buiild, quitting XCode, etc, with no luck.
Then I realised I had no -Bridging-Header.h file in my project, presumably due to the way I'd cobbled it together from a previous project. Shouldn't be a problem because I was not (yet) calling Objective-C from Swift. But when I added a bridging header, and referred to its path in the build settings (Swift Compiler - Code Generation -> Objective-C Bridging Header), it magically fixed the problem - my -Swift.h file was suddenly full of SWIFT_CLASS() goodness!
So I'm guessing the bridging header is fundamental to the process, even if you're NOT using Objective-C from Swift.
UPDATE: I finally understand this. It is related to public/internal access modifiers. Not sure if I missed this originally or if it's an addition to the Apple docs, but it now clearly states:-
By default, the generated header contains interfaces for Swift
declarations marked with the public modifier. It also contains those
marked with the internal modifier if your app target has an
Objective-C bridging header.
It is proper to use #import "TestAppModule-Swift.h" in your .m files. If you need to reference a class in a .h, use the #class forward declaration.
Further, if you want to use a Swift class from Objective-C, the Swift class must be marked with the #objc attribute. Xcode will only include classes with that attributed in the generated header. See also this documentation.
Class should be declared as #objc public class
A more convenient way would be to inherit from NSObject. Like so:
class HelloWorld: NSObject {
func hello() {
println("hello world")
}
}
In my case, by following Apple guidelines, it did not work until I ran the project. The xcode editor kept flagging the unknown swift class, until i clicked "run". The build succeeded, and the swift method worked.
In my case the class was not being compiled, because I first added it to my test target only... After adding it to my main target (Build Phases -> Compile Sources), it was actual compiled and added to the header file.
So much for TDD ;-)
Maybe you defined a Swift class with the same name as an existing Objective-C class which wouldn't be unusual if you want to refactor your Objective-C code to Swift.
As long as you have a class defined simultaneously in Swift and Objective-C the compiler quietly stops updating the bridging header altogether ("ProductModuleName-Swift.h") - which also affects subseqeuent changes in other bridged Swift files.
For general reference how to import Swift into Objective-C see:
Importing Swift into Objective-C | Apple Developer Documentation