I'm trying to call an Objective-C class from Swift. So I enabled the bridging header option
Created the following files:
MyTest.h:
#import <Foundation/Foundation.h>
#interface MyTest : NSObject
+(void)sayHello;
#end
MyTest.m
#implementation MyTest
+(void)sayHello {
NSLog(#"Hello");
}
#end
at MyProject-Bridging-Header.hadded:
#import "MyTest.h"
Then when in a Swift file I call:
let test = MyTest()
test.sayHello()
The compiler complains in the second line:
MyTest does not have a member named 'sayHello'
What am I doing wrong?
Note: I have no experience with Objective-C.
You created a class method, not an instance method.
Try instead:
MyTest.sayHello()
Or change the objective-c function to:
-(void)sayHello
Note the - instead of the +. See this question and answers for further reading.
Related
I have been trying with no success the following structure:
ClassA.swift
class ClassA:NSObject{
var varA = ""
}
then I have a ClassB.h and ClassB.m (Objective c) and I am not able to define "Project-Swift.h" in the .h file so i import it into the .m
#interface ClassB()
#property ClassA *myClassA;
#end
and
#synthesize myClassA = theAClass;
The problem comes when I try
class ClassC:NSObject{
let theClassAFromC = ClassB.myAClass
}
I get an error message Value of type 'ClassB' has no member 'theClassA'
Add your objc header to bridging header
In your objc header use #class notation for your swift class, e.g. #class ClassA;, instead of import "Project-Swift.h" file. You can import that one in your objc implementation file.
Don't forget that you cannot access non-static property of objc class the way you're declaring. Instead, initialize your ClassB object in your swift class and access it's property when needed. For instantiating the ClassA object you can use dependency injection in ClassB
As part of the convenience, use #objc declaration for your Swift classes accesible to objc runtime
try to search with keyword "Bridging-Header" and then add
#import "ClassB.h"
That does not work in my case.
adding ClassB.h in my Bridge File makes properties from .h Visible But not the the properties in my .m file. If i add Class.m In my header file then Module-Swift.h is not found
Hi I'm new to Swift but experienced with Objective-C.
I have a project that uses both Swift and Objective-C files (bridging and all).
Say I have a protocol called "fooProtocol" and a class "foo" that implements it. I am trying to pass an object of type "fooProtocol" from the Swift file as a parameter to the function inside the Objective-C file.
here is the Objective-C function inside class "tester":
-(void)setWithFoo:(id<fooProtocol>*)_foo{
}
here is the Swift code:
var myObject:fooProtocol = foo.init()
var objcObject:tester = tester.init()
objcObject.setWithFoo(_foo: myObject)
It first says "Cannot convert value of type "fooProtocol" to expected argument type "AutoreleasingUnsafeMutablePointer (obviously because it needs to be passed by reference, so...)
I then tried casting the parameter to this:
tester.setWithFoo(_foo: AutoreleasingUnsafeMutablePointer<fooProtocol>(myObject))
Now the error reads: "Cannot invoke initializer for type 'AutoreleasingUnsafeMutablePointer with an argument list of type '(fooProtocol)'
I have tried many more permutations and variations but I simply cannot stop the compiler error. For such a simple procedure as passing a polymorphic variable to a function in Objective-C file that expects that protocol id, Swift has made it a nightmare.
...Any help would be appreciated, thanks!
=== EDIT ===
Here are the declarations for the classes, now starting properly with caps
In the "FooProtocol.h" file:
#protocol FooProtocol
#end
In the "Foo.h" file:
#import <Foundation/Foundation.h>
#import "FooProtocol.h"
#interface Foo : NSObject <FooProtocol>
#end
In the "Foo.m":
#import "Foo.h"
#implementation Foo
#end
The "FooProtocol.h" file:
#import <Foundation/Foundation.h>
#protocol FooProtocol
#end
The "Tester.h" file:
#import <Foundation/Foundation.h>
#import "FooProtocol.h"
#interface Tester : NSObject
-(void)setWithFoo:(id<FooProtocol>*)_foo;
#end
The "Tester.m" file:
#import "Tester.h"
#implementation Tester
-(void)setWithFoo:(id<FooProtocol>*)_foo{
//do something with _foo
}
#end
And again the Swift code that can't compile:
var myObject:FooProtocol = Foo.init()
var objcObject:Tester = Tester.init()
objcObject.setWithFoo(AutoreleasingUnsafeMutablePointer<FooProtocol>(myObject))
You probably don't mean to say this:
-(void)setWithFoo:(id<FooProtocol>*)_foo;
It is very unusual to see an id* in Objective-C. In fact, it's so unusual that in all my years of programming Cocoa, I have never seen one.
You probably mean this:
-(void)setWithFoo:(id<FooProtocol>)_foo;
And then you will be able to say, on the Swift side:
objcObject.setWithFoo(myObject)
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
I am trying to build the Clustering Plug in my project under Leopard. I have following two questions.
In the project an interface class is defined as
#interface ClusteringController : NSWindowController
{
.......
.....
....
}
#end.
And this class is used in implementation class using forward declaration:
#class ClusteringController;
then in one function it is used as:
- (long) filterImage:(NSString*) menuName
{
ClusteringController *cluster = [[ClusteringController alloc] init];
[cluster showWindow:self];
return 0;
}
When I build this project it produces the warning:
warning: receiver 'ClusteringController' is a forward class and corresponding #interface may not exist
Also there is one more warning produced:
warning: no '-updateProxyWhenReconnect' method found
This warning is coming for the following line of code:
if(delegate) [delegate updateProxyWhenReconnect];
Can anybody help me to overcome these warnings?
A forward declaration is used when the header file will be imported after the interface. It looks to me that you've used the #class directive after the interface for the class itself.
The normal use of a forward class declaration looks like this:
#import "SomeSuperClass.h"
#class Forwardclass;
#interface SomeClass : SomeSuperClass
{
Forwardclass anIvar;
}
#property Forwardclass anIvar;
#end
#import "SomeClass.h"
#import "ForwardClass.h"
#implementation SomeClass
#synthesize anIvar;
-(void) setAnIvar:(ForwardClass *) aForwardClass;
#end
The #class directive is never used in an implementation (.m) file.
That's not what #class is for.
You use #class in the header file for another class, to tell the compiler that the class you're declaring does exist. Without it, the compiler would not know that that's a class name, and when you declare a variable as holding a pointer to an instance of that class, the compiler would think that you're just making up words. Using #class is called forward-declaring the class.
Your situation is different. You're in the implementation file for that class.
What the compiler needs from you now is the class's #interface. The warning is telling you that the compiler needs an #interface, but you haven't given it one (so, as far it knows, the #interface “may not exist”).
Normally, you would have written the #interface in a header file; how now to get it into the implementation file?
That's where the preprocessor comes in, with its #import directive. At the top of the implementation file (ClusteringController.m), import the header file:
#import "ClusteringController.h"
The preprocessor will replace this with the contents of that file, then hand the preprocessed code to the compiler, which will see the #interface there.
I have the following objective-C++ header with the simple method to return this pointer.
#interface MyObj
{
MyCPPObj * cpp;
}
-(MyCPPObj *) getObj;
I have created the simple method
#implementation MyObj
-(MyCPPObj *) getObj
{
return cpp;
}
Everything seems to work until I actually try to use the object in another file
newObj = [createdMyObj getObj];
It complains: error: cannot convert 'objc_object*' to 'MyCPPObje *' in initialization.
It seems that the method is return an objective-c object, but I specifically requested a C++ pointer.
MyCPPObj is an honest C++ class:
class MyCPPObj
{
public:
int x;
}
How can I fix that?
On my 10.6.3 machine, the following combination worked without any problem: aho.h
#import <Foundation/Foundation.h>
class MyCPPObj{
};
#interface MyObj:NSObject
{
MyCPPObj * cpp;
}
-(MyCPPObj *) getObj;
#end
and aho.mm
#import <Foundation/Foundation.h>
#import "aho.h"
void foo(){
MyObj*objcObj=[[MyObj alloc] init];
MyCPPObj*cppObj=[objcObj getObj];
}
Two pitfalls you might have fallen into:
Unlike C++, a class in Objective-C which doesn't inherit from NSObject won't work. (Well, you can make it work, but you don't want that usually.) Note the line #interface MyObj:NSObject.
To use NSObject, do #import <Foundation/Foundation.h>
Don't forget to use the extension .mm for Objective-C++ files.
Most likely you have forgotten to #import the header file with the #interface into the .mm file where you use getObj.
The error states what happens, and JeremyP is right on the money. When you forget to include a header file with the prototypes of the selectors, the compiler assumes the selector returns an object of type id. Well id is a typedef to objc_object*, which is incompatible with your C++ class. To fix the error, you simply need to include your header file in the file where you called getObj.