In my project i have many swift classes that extend generic classes. And Now i'm in a need to send data from objective-c class to these swift classes. Is there any possible way to do this ?
I have tried using #objc before class as shown below
but it didn't allow me to do this.
I followed this answer stack link. But i checked when i run my app with this code it dint create the variable in the Project-swift class as shown in below image
as the variable is not created here so it gives error while calling the variable in objective-c class.
Kindly help out with better solution.
I got my solution by creating another class which contain a protocol and i indirectly call the generic extended class.
class EntityDataTable :BaseData<EntitySw> {
}
this is the generic extended class
and the another class i made to indirectly access this class in objective-c is
#objc class EntityService : NSObject {
var entityProtocol:EntityDataProtocol?
override init() {
super.init()
entityProtocol = returnDataObject()
}
func returnDataObject() -> EntityDataTable {
return EntityDataTable()
}
}
#objc protocol EntityDataProtocol{
func addFromService(source: CWEntity)
func getAll() -> [EntitySw]
}
Then i imported the Project-swift.h file in objective c class and made the object of swift class
Related
I'm merging my Swift project with already existing Objective-C code. I need to call some important methods of Swift class from objective C app delegate. I tried all methods given in net, but it was no use. Can any one help me out?
Yes, it's possible but with some limitations.
You can use only classes which inherited from NSObject, with public attribute and marked with #objc. At Objective-C code you should import "ProductModuleName-Swift.h" file which generated by compiler.
Here is an example of Swift class:
import Foundation
#objc public class ExampleClass: NSObject {
#objc public var someInstanceProperty = "Property"
#objc public func someFunction() {
print("Some function")
}
}
Notice that this class inherited from NSObject and have #objc and public attributes. After command+B you can take a look at generated bridge header through Assistance editor:
Then you should import the bridge header at your Objective-C class.
#import "ProductModuleName-Swift.h"
And then you can use your Swift class at Objective-C code like any other Objective-C class:
__auto_type const someClass = [ExampleClass new];
[someClass someFunction];
NSLog(#"%#", someClass.someInstanceProperty);
Here is an additional information from Apple:
Importing Swift into Objective-C
I am working on iOS app which is having Obj C code as well as Swift. I am migrating my existing Objective C category to swift code. But when I override existing method in swift extension, it is not compiling. Swift extension is working well for new methods but not for overriding existing methods.
Code:
extension UIViewController {
public override func shouldAutorotate() -> Bool {
return false
}
public override func supportedInterfaceOrientations() -> UIInterfaceOrientationMask {
return UIInterfaceOrientationMask.Portrait
}
}
Error:
Method 'shouldAutorotate()' with Objective-C selector 'shouldAutorotate' conflicts with previous declaration with the same Objective-C selector
Method does not override any method from its superclass
Method 'supportedInterfaceOrientations()' with Objective-C selector 'supportedInterfaceOrientations' conflicts with previous declaration with the same Objective-C selector
Here, Am I missing anything?
I am using Xcode 7.3.1 and Swift 2.x
EDIT:
From below Answers, I got to know that We cant change behaviour of existing method of class at runtime in Swift extension like in Objective C Categories. Here I should make a base class which will override method and I should use all my ViewControllers as child classes from new base class as parent.
But in my case, I want to change behaviour of all "shouldAutorotate" methods including 3rd party frameworks UIViewController. In above case I cant force all third party frameworks UIviewControllers to become subclass of my base class. In Objective C i could achieve this.
Swift extensions aren't to be used to override methods declared in the class they're extending – especially for Objective-C classes, that's very much like providing two definitions of the same method in the same class. Imagine seeing a class that looked like:
class UIViewController : UIResponder {
public func shouldAutorotate() -> Bool {
return true
}
public func shouldAutorotate() -> Bool {
return false
}
}
Which one wins? That's the conflict you're being warned about.
If you need to override methods for a view controller of yours, you'll need to do that in a subclass, not an extension.
Ninja edit: this may have been possible to do in Objective-C, but was a programming error there. If a category duplicates a method from a main class, which definition gets used is undefined. See this SO post and the backing Apple documentation.
I learn the Swift Language and i need to create a manager like a Parse sdk.
For exemple when you initialize your Parse in app you write
Parse.setApplication("...", applicationId:"...")
And later you can write code like this
Parse.doSomething()
The method doSomething() use initial context.
Can you show me in my class should look like? I try some singleton exemple, but a have MyClass.sharedAttribute.doSomething() in case
What you have shown is no indication of singletons whatsoever, it sounds and looks more like a static class with static members and properties:
class MyStatic {
static var appIdA : String?
class func setApplicationId(a : String) {
appIdA = a
}
class func doSomething() {
print(appIdA)
}
}
MyStatic.setApplicationId("blabla")
MyStatic.doSomething() // prints Optional("blabla")
Of course there is the possibility that internally the class is a singleton, but Parse does not seem to be one, just looking at the functions it exposes.
The code comments even state
/*!
The `Parse` class contains static functions that handle global configuration
for the Parse framework.
*/
I had following confusion. As far as I know the main difference between static and class keywords when declaring method is that the second one could be overridden in subclasses.
The problem
However when I declare a protocol in Swift 1.2 like this:
protocol MyProtocol
{
class func dummyClassMethod()
}
compiler gives an error:
Class methods are only allowed within classes; use 'static' to declare
a static method
The error is pretty descriptive as obviously MyProtocol is not a class, however I want to make a class func part of the protocol.
What I've tried
I've found that if I declare interface in protocol as static, compiler is happy and I could use this static method in all classes that adopt this protocol:
protocol MyProtocol
{
static func dummyClassMethod()
}
The question
So my question basically is is this right? This declaration states that my class method cannot be overridden in children, however in my implementation I could write and use the following:
class ClassA: MyProtocol
{
class func dummyClassMethod() {
}
}
class ClassB: ClassA
{
override class func dummyClassMethod() {
}
}
and now my dummyClassMethod is not static anymore...
Compiler is Ok and everything works - but why?
Is it specific to the fact that interface itself is static, however
it's implementation is not?
Is there a better alternative for class func in protocols?
Objective-C solution
In ObjC this is pretty easy and compile & run flawlessly:
#protocol MyProtocol
+(void)dummyClassMethod;
#end
You can review Apple's Documentation (subsection Method Requirements).
There says:
As with type property requirements, you always prefix type method requirements with the static keyword when they are defined in a protocol. This is true even though type method requirements are prefixed with the class or static keyword when implemented by a class
In practice, You can do it as follow:
First, declare your protocol:
protocol SomeProtocol {
static func someMethod()
}
Then, in your class you've 2 options:
First:
class SomeClass : SomeProtocol {
class func someMethod()
}
Second:
class SomeClass : SomeProtocol {
static func someMethod()
}
I hope, this may clarify your doubt..
https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html
A protocol defines a blueprint of methods, properties, and other
requirements that suit a particular task or piece of functionality.
The protocol doesn’t actually provide an implementation for any of
these requirements—it only describes what an implementation will look
like. The protocol can then be adopted by a class, structure, or
enumeration to provide an actual implementation of those requirements.
After this protocol definition it becomes reasonable that
As with type property requirements, you always prefix type method
requirements with the static keyword when they are defined in a
protocol. This is true even though type method requirements are
prefixed with the class or static keyword when implemented by a class...
To make protocol method static and final implement that method with static keyword
class ClassA: MyProtocol{
static func dummyClassMethod() {
}
}
and now you cant override dummyClassMethod function anymore. If you want to prevent overriding only you must declare protocol method as final. About class functions, they were not fully supported in Swift 1.0 and now in Swift 1.2 I think that they are moving towards static functions
This is my inheritance structure
Protocols
protocol BaseProtocol {
}
protocol ChildProtocol: BaseProtocol {
}
Classes
class BaseClass: NSObject {
var myVar: BaseProtocol!
}
class ChildClass: BaseClass {
override var myVar: ChildProtocol!
}
I'm receiving a compiler error:
Property 'myVar' with type 'ChildProtocol!' cannot override a property with type 'BaseProtocol!'
What is the best approach to achieve this?
UPDATE
I updated the question trying to implement the solution with generics but it does not work :( This is my code (now the real one, without examples)
Protocols
protocol TPLPileInteractorOutput {
}
protocol TPLAddInteractorOutput: TPLPileInteractorOutput {
func errorReceived(error: String)
}
Classes
class TPLPileInteractor<T: TPLPileInteractorOutput>: NSObject, TPLPileInteractorInput {
var output: T!
}
And my children
class TPLAddInteractor<T: TPLAddInteractorOutput>: TPLPileInteractor<TPLPileInteractorOutput>, TPLAddInteractorInput {
}
Well, inside my TPLAddInteractor I can't access self.output, it throws a compiler error, for example
'TPLPileInteractorOutput' does not have a member named 'errorReceived'
Besides that, when I create the instance of TPLAddInteractor
let addInteractor: TPLAddInteractor<TPLAddInteractorOutput> = TPLAddInteractor()
I receive this other error
Generic parameter 'T' cannot be bound to non-#objc protocol type 'TPLAddInteractorOutput'
Any thoughts?
#tskulbru is correct: it can't be done, and this has nothing to do with your protocols. Consider the example below, which also fails…this time with Cannot override with a stored property 'myVar':
class Foo {
}
class Goo: Foo {
}
class BaseClass: NSObject {
var myVar: Foo!
}
class ChildClass: BaseClass {
override var myVar: Foo!
}
To understand why, let's reexamine the docs:
Overriding Properties
You can override an inherited instance or class property to provide
your own custom getter and setter for that property, or to add
property observers to enable the overriding property to observe when
the underlying property value changes.
The implication is that if you are going to override a property, you must write your own getter/setter, or else you must add property observers. Simply replacing one variable type with another is not allowed.
Now for some rampant speculation: why is this the case? Well, consider on the one hand that Swift is intended to be optimized for speed. Having to do runtime type checks in order to determine whether your var is in fact a Foo or a Bar slows things down. Then consider that the language designers likely have a preference for composition over inheritance. If both of these are true, it's not surprising that you cannot override a property's type.
All that said, if you needed to get an equivalent behavior, #tskulbru's solution looks quite elegant, assuming you can get it to compile. :)
I don't think you can do that with protocols
The way i would solve the problem you are having is with the use of generics. This means that you essentially have the classes like this (Updated to a working example).
Protocols
protocol BaseProtocol {
func didSomething()
}
protocol ChildProtocol: BaseProtocol {
func didSomethingElse()
}
Classes
class BaseClass<T: BaseProtocol> {
var myProtocol: T?
func doCallBack() {
myProtocol?.didSomething()
}
}
class ChildClass<T: ChildProtocol> : BaseClass<T> {
override func doCallBack() {
super.doCallBack()
myProtocol?.didSomethingElse()
}
}
Implementation/Example use
class DoesSomethingClass : ChildProtocol {
func doSomething() {
var s = ChildClass<DoesSomethingClass>()
s.myProtocol = self
s.doCallBack()
}
func didSomething() {
println("doSomething()")
}
func didSomethingElse() {
println("doSomethingElse()")
}
}
let foo = DoesSomethingClass()
foo.doSomething()
Remember, you need a class which actually implements the protocol, and its THAT class you actually define as the generic type to the BaseClass/ChildClass. Since the code expects the type to be a type which conforms to the protocol.
There are two ways you can go with your code, depending what you want to achieve with your code (you didn't tell us).
The simple case: you just want to be able to assign an object that confirms to ChildProtocol to myVar.
Solution: don't override myVar. Just use it in ChildClass. You can do this by design of the language Swift. It is one of the basics of object oriented languages.
Second case: you not only want to enable assigning instances of ChildProtocol, you also want to disable to be able to assign instances of BaseProtocol.
If you want to do this, use the Generics solution, provided here in the answers section.
If you are unsure, the simple case is correct for you.
Gerd