Accessing Objective-c base class's instance variables from a Swift class - ios

Question

Having an Objective c base class:
#interface ObjcClass : NSObject {
NSString *aVariable_;
}
And a swift sub-class:
class SwiftClass : ObjcClass {
func init() {
// aVariable_ can't be accessed here. An Objective-c derived
// class has direct access to it's super's instance variables!
}
}
How do I access ObjcClass aVariable_ from within SwiftClass?

Answer 1

Great query. We have tried to hard to get this done. The only working solution I found
get value by using self.valueForKey("aVariable_")
set value using self.setValue("New Value", forKey: "aVariable_")
Hope that helps. Possible solution without altering super class.

Answer 2

I couldn't find a "proper" way to do this, but I needed badly for it to work. My solution was to create a simple getter method in my Objective C superclass, like this:
header file
#interface ObjcClass : NSObject {
NSString *myVariable;
}
- (NSString *)myVariable;
in the implementation file
- (NSString *)myVariable {
return myVariable;
}
I'd love to hear of a better way of doing it, but this at least works.

Answer 3

I've searched a lot for this.
Eventually I changed my code from:
#interface PrjRec : NSObject {
#public
NSString* name;
}
#end
To:
#interface PrjRec : NSObject {
}
#property NSString* name;
#end
similar to #JasonTyler solution.
Then I can access to my object property from Swift code with simple dot notation <object instance>.name,
But I needed to change all existing objective-c references from
<object instance>->name
To:
<object instance>.name
or
_name
if inside class unit.
I hope for a better solution too.

Answer 4

This worked as a pretty neat solution for me, just adding a Swift variable like:
var myInstanceVar: String {
return self.value(forKey: "myInstanceVar") as! String
}

Answer 5

If you are willing to have a property, then you can create the property to fit your needs.
#interface ObjcClass : NSObject {
NSString *aVariable_;
}
#property (nonatomic) NSString *aVariable_;
...
#implementation ObjcClass
#synthesize aVariable_ = aVariable_;
This allows the variable to be accessed as inst->aVariable_ or as inst.aVariable_. In the Objective C class the variable can be accessed as aVariable_ or self.aVariable_.

Answer 6

I seriously don't know why anyone does instance variables anymore (for one, they're private by default) vs properties. See Giorgio Calzolato's answer on this (apart from his last line about looking for a better solution - that IS the best solution :) ).
In my case I already had a property and was extra perplexed over why it didn't work. But I realized that the property had a custom time and it needed to be added into my SDK-Bridging-Header.h file.
So if your property is set to a custom type like this:
#property (nonatomic, weak) IBOutlet SDKMyCustomObject *customObject;
...then remember to add it to the bridging header.