I have an old Objective C class
// Model.h
#interface Model
#end
#protocol Observer
- (void)observer:(ObserverManager *)observerManager someType:(SomeType)someType
#end
and then in implementation file
//Model.m
#interface Model () <Observer>
#end
#pragma mark Observer
- (void)observer:(ObserverManager *)observerManager someType:(SomeType)someType
{
if (someType && [self.delegate respondsToSelector:#selector(someMethod)]) {
[self.delegate someMethod];
}
}
Now, I need to write a test to verify that the delegate method someMethod will get called. I am trying to write a test in Swift and there is no simple way to mock ObserverManager so I am trying to call the method delegate method directly on the model. The problem I have is that I can't figure out how to call
- (void)observer:(ObserverManager *)observerManager someType:(SomeType)someType
on the model in Swift. Since objc class conforms in the implementation file it's invisible for Swift and it gives me compiler error.
I was trying to have a private objc header where I would make delegate method visible and then include that file into tests bridging file but the compiler still complains. Any other ideas I can try?
Thanks
Related
I'm trying to combine two plugins written in Objective-C. I have Plugin1 and Plugin2 which execute fine enough independently. I'm trying to add the Plugin2.m code to my Plugin1 Classes folder and execute both at the same time.
When I do this, Plugin1.m seems to execute first, I guess because it has IBAction calls and Plugin2.m doesn't? This is fine, but I'd like to run Plugin2.m within a function in Code1.m. So In the code below, when the IBAction call in Plugin1 is initiated I would like it to do what Plugin2 normally does and then continue with Plugin1 methods.
Plugin1.h:
#import Plugin2.h
#interface Plugin1: NSWindowController {
...
}
+(void) Plugin2;
#end
Plugin1.m:
#import "Plugin1.h"
#import "Plugin2.h"
#implementation Plugin1
-(id) loadPlugin1
{
...
}
-(IBAction) computeStuff:(id)sender
{
[self Plugin2];
//Plugin2* testRun = [Plugin2 alloc] init];
...do other stuff
}
#end
Plugin2.h
#interface Plugin2 : PluginFilter {
...
}
#end
Plugin2.m:
#import Plugin2.h
#implementation Plugin2
-(void) initPlugin
{
...
}
#end
Unfortunately I can't troubleshoot this from within Xcode, I have to install and test the plugin on my program to test. But when I keep an eye on Console and try the above I get "-[Plugin1 Plugin2]: unrecognized selector sent to instance 0x7....
in your plugin1 interface you defined
+(void)plugin2;
but implemented no method
+(void)plugin2 {
}
when you invoke + method you need to tell which class you call the method from because self refers to an object and not the class.
[self.class plugin2];
// OR
[Plugin1 plugin2];
Hints: try to follow naming conventions in objective-c.
This will help you distinguish if a definition is a -method: or Class
Consider reading about delegate design patterns and the use of <Protocols>
Also define special -initPlugin in your Plugin2 implementation and use a return type. Otherwise you initialise nothing.
-(instancetype)initPlugin;
I have an objective-c class something like:
#interface MyClass: NSObject { }
- (MyObject *)coolMethod;
#end
#implementation MyClass
- (MyObject *)coolMethod {
return [self doCoolStuff];
}
#end
...and a Swift extension something like:
extension MyClass {
#objc func addedMethodInSwift() {
let coolObj = coolMethod() // <<<< compiler error - method not found
}
}
The code will not compile, because the compiler cannot find the implementation of coolMethod(), however certain other methods from the Objective-C class can be called from the Swift extension.
I have checked and the Objective-C header file is included in the project's bridging header, so it should be visible to Swift. The method in question is definitely visible in the header file.
Why can't coolMethod() be called from the Swift extension?
Check that both your objective-C class and the return type of the function (in your case MyObject.h) are included in the Bridging header. Methods with return types not included in the bridging header are not available from Swift.
Environment: Xcode 6.1.1 & Xcode 6.2 Beta
Greetings:
I need to publish a NSString within a Swift doc from a neighboring Objective-C doc within the same project. For example, display "Hello World" generated in Objective-C upon a Swift page. I've made a proof-of-concept demo; based on feedback.
I'm thinking of using an ObjC --> Swift delegate via a protocol pattern as shown below:
Note: the Swift file is the delegate.
Here I'm calling the delegate method in Swift, from Objective-C:
#pragma mark - Action methods
- (IBAction)sendDelegateAction:(UIButton *)sender {
[_delegate radiusString:#"Hello World"];
}
I've instantiated the Objective-C file to link the delegate to the instance (I hope I got it right):
let geo32Controller = MyObjCTableViewController()
geo32Controller.delegate = self
So far, the compiler complained that the Swift protocol couldn't be found.
Here's the protocol (declared in Swift):
#objc protocol DiscoveryContributeProtocol {
// optional
func radiusString(radiusString:String)
}
And here's the delegate reference to that protocol in the Objective-C header file:
#interface MyObjCTableViewController : UIViewController<UITableViewDelegate, UITableViewDataSource>
#property (nonatomic, weak) id<DiscoveryContributeProtocol> delegate;
#end
However, the compiler can't find the protocol:
BTW: when I put the bridge reference in the ObjC's header file, I get a compiler error:
Two Questions:
Do I have the correct pattern (did I instantiate the ObjC correctly) ?
How do I make the Objective-C portion see the Swift protocol for the delegate link?
You have the right idea, but have a few bugs that are preventing this from working.
You've declared Geo32Boundaries as conforming to the DiscoveryContributeProtocol, but it doesn't need to and doesn't actually implement it, it only has a property that conforms to that protocol. That's the source of the "Method 'radiusString:' not implemented" error:
#interface Geo32Boundaries: UIViewController // <-- that's all you need
You're setting the delegate incorrectly -- the code you have there looks like it's trying to set a class instance of Geo32Boundaries to self, but you're also trying to call it like a function. You'll need to set the delegate on a the instance of the Geo32Boundaries view controller that is being presented to the user. I don't know where that code lives, so I can't give a great example, but it'll be something like:
geo32Controller.delegate = self
Lastly, though not a bug, your protocol should really be called DiscoveryContributeDelegate -- we usually don't use "protocol" in the protocol name.
Another way of phrasing this question: is it possible for a subclass to be a delegate of its super class? I'm trying to make my code reusable within my app and have a situation where the subsclass needs to implement two methods for it to be functional. How can I ensure this occurs? Or what is the proper way of defining these methods?
Update
I didn't mean to imply that I want the compiler to generate flags. I just want a clean way of organizing my code. Currently I override methods of the superclass. Using that approach the superclass can call [super methodToOverride] and it works. However this doesn't feel very clean to me as there's no way to specify "these are the methods you should override" aside from putting a comment somewhere.
In obj-c, it is not possible to force subclasses to overwrite methods of its superclass. But you can raise an exception in the superclass, should it ever be called because the subclass did not implement a certain method.
But a subclass can be a delegate of its superclass, if the superclass does not implement certain methods, and you can enforce that the delegate implements these methods, if the superclass specifies the protocol, i.e. required methods, and the subclass adopts it.
If you want to force your subclass to implement methods from super class, you can do this as below:
//In super class
- (id)someMethod:(SomeObject*)bla
{
[self doesNotRecognizeSelector:_cmd];
return nil;
}
Your app will crash if subclass will not implement this method and you don't need to call
[super someMethod:bla];
There is no way to do this in compile time. However you can raise an exception in the base class.
Something like this:
#throw [NSException exceptionWithName:NSInternalInconsistencyException
reason:[NSString stringWithFormat:#"You must override %# in a subclass", NSStringFromSelector(_cmd)]
userInfo:nil];
If your question is "how can I get the compiler to flag that a certain class doesn't implement a certain function" then I would say
Define a protocol with non-optional methods -- "By default, all methods declared in a protocol are required methods. This means that any class that conforms to the protocol must implement those methods."
Define a class ("stub") that declares it implements the protocol
Now when a subclass of your stub class is written, the compiler will flag it as an error if the mandatory method(s) aren't implemented
I know that it's awful, but supposed that you need to do this since your 3rdParty SDK requires this design pattern, you could use a Factory pattern:
Supposed then to have the base class MyParentAPIClient and two sub classes like MyFacebookAPIClient and MyGooglePlusAPIClient and that you do something like
self.myAPIClient = [MyParentAPIClient alloc] initWithAPIKey:apiKey];
and that you have defined
##interface MyParentAPIClient : NSObject {
}
-(void)callAPI;
#end
and you have override this in the two subclasses
#implementation MyFacebookAPIClient
-(void)callAPI {
[super callAPI];
// do something specific for this api client
}
#end
and
#implementation MyGooglePlusAPIClient
-(void)callAPI {
[super callAPI];
// do something specific for this api client
}
#end
Then you are doing in your controller
[self.myAPIClient callAPI];
but the super class MyParentAPIClient method is being called.
Now you could do a factory in the base class like:
-(void)callAPI {
if([self isKindOfClass:[MyFacebookAPIClient class]]) {
[((MyFacebookAPIClient*)self) callAPI];
} else if([self isKindOfClass:[MyGooglePlusAPIClient class]]) {
[((MyGooglePlusAPIClient*)self) callAPI];
}
}
Of course this have a downside that is to do not call the super in the sub classes that now become:
#implementation MyFacebookAPIClient
-(void)callAPI {
// [super callAPI]; the factory method called that
// do something specific for this api client
}
#end
and
#implementation MyGooglePlusAPIClient
-(void)callAPI {
// [super callAPI]; being called in the factory
// do something specific for this api client
}
#end
The good news is that there is no change in the methods calls since as soon as you call from the controller:
[self.myAPIClient callAPI];
You will have the calls
[MyParentAPIClient callAPI]; // parent class
[MyFacebookAPIClient callAPI]; // sub class
The other downside is that the parent class must known the subclass instances.
Now if we take a look at the factory:
if([self isKindOfClass:[MyFacebookAPIClient class]]) {
[((MyFacebookAPIClient*)self) callAPI];
} else if([self isKindOfClass:[MyGooglePlusAPIClient class]]) {
[((MyGooglePlusAPIClient*)self) callAPI];
}
}
we could make it better like in several way. Take a look at Dynamic type cast from id to class in objective c and Is there an equivalent to C++'s dynamic cast in Objective-C? or Objective-C dynamic_cast?
Good luck!
The UIGestureRecognizerSubclass.h pattern from UIKit is worth a look, that has all the protected methods that should be overridden and that header is not in the framework include, it is only included in subclasss' .m files. Also, nowadays you can tag methods with NS_REQUIRES_SUPER to require overrides to call super, however it can only be used in interfaces, not protocols so that might influence your design.
For super advanced code, NSAccessibilityProtocols.h in AppKit uses a protocol tag to require subclasses to re-implement methods, even if already implemented by a superclass. Here is an example of that you can paste right into in header in your currently open Xcode project:
NS_PROTOCOL_REQUIRES_EXPLICIT_IMPLEMENTATION
#protocol Protocol
#property (readonly) id theWorstOfTimes;
// -(void)testMethod; // uncomment to test problem
#end
// In this example, ClassA adopts the protocol.
#interface ClassA : NSObject <Protocol>
#property (readonly) id theWorstOfTimes;
#end
#implementation ClassA
- (id)theWorstOfTimes{
return nil; // default implementation does nothing
}
-(void)testMethod{}
#end
// This class subclasses ClassA (which also adopts 'Protocol').
#interface ClassB : ClassA <Protocol>
#end
#implementation ClassB // expected-warning {{property 'theWorstOfTimes' requires method 'theWorstOfTimes' to be defined - use #synthesize, #dynamic or provide a method implementation in this class implementation}}
#end
In Xcode you'll see a yellow line at ClassB's expected-warning that the property method is missing. NS_PROTOCOL_REQUIRES_EXPLICIT_IMPLEMENTATION is just a macro for __attribute__((objc_protocol_requires_explicit_implementation)) and this code sample is modified from the test harness of that feature here.
Although this looks great there is a slight problem. Currently this only works for methods that implement protocols, it used to work also for methods but a bug has been introduced in 2014 via a misunderstanding on the purpose of this feature and thus now it is limited to property methods. I have emailed the author to make them aware so hopefully it changed back to its original and proper behavior. To test the bug you can uncomment the method in the protocol and you will see there is no warning in ClassB. Hopefully you can change some of your methods to read-only properties to at least get some use out of it. On the plus side when Xcode offers to "Fix" the issue it does add stubs for the missing methods.
Here is some documentation on NS_PROTOCOL_REQUIRES_EXPLICIT_IMPLEMENTATION:
ImplementingAccessibilityforCustomControls
nsaccessibilitybutton
If you used this then pat yourself on the back for becoming an ObjC expert if you weren't already!
I am learning object orientated programming from the online Stanford courses there is a part I am unsure of regarding declarations. I thought that you must always declare the prototype in the header and then write the code in the implementation file, but the professor wrote a method in the implementation without a declaration prototype in the header file, how come?
Also, may someone please clear the difference between private and public and if the method without a prototype is public or private? The method without a prototype is not from a super class.
That is a perfectly legal way to declare methods that are not to be used outside the class implementation itself.
The compiler will find methods in the implementation file as long as they precede the method in which they are used. However that will not always be the case, as the new LLVM compiler allows methods to be declared in any order and referenced from a given file.
There are a couple of different styles for declaring methods inside an implementation file:
//In the Header File, MyClass.h
#interface MyClass : NSObject
#end
//in the implementation file, MyClass.m
//Method Decls inside a Private Category
#interface MyClass (_Private)
- (void)doSomething;
#end
//As a class extension (new to LLVM compiler)
#interface MyClass ()
- (void)doSomething;
#end
#implementation MyClass
//You can also simply implement a method with no formal "forward" declaration
//in this case you must declare the method before you use it, unless you're using the
//latest LLVM Compiler (See the WWDC Session on Modern Objective C)
- (void)doSomething {
}
- (void)foo {
[self doSomething];
}
#end
If you write the method in you header file it is public and accessible for other classes / objects. If you do not declare it in the header file the method is a private method meaning that you can access it internally in you class but no other class can use this method.