Creating an Objective-C equivalent Getter and Setter in Swift

Your assumption was close, but a few things could be changed. I will try to help you get as close as possible to the Objective-C version.

First of all, the nonatomic and assign are irrelevant in swift. That leaves us with

@property (getter = isOpen) BOOL open;

Since properties in swift are just instance variables, the swift translation would be as follows.

var open:Bool

Although this has the same basic functionality as the Objective-C version, it is lacking the named getter (isOpen). Unfortunately, there is no direct translation to swift for this (yet). You could use a custom getter and setter.

var open:Bool {
    get {
        // custom getter
    }
    set {
        // custom setter
    }
}

A rather crude work around would be to make another function literally called isOpen that would act as a getter.

func isOpen() -> Bool { return self.open }

In conclusion, what you are asking is only slightly possible, but hopefully in later releases of swift can become a reality.

var open: Bool {
    @objc(isOpen)
    get {
        // custom getter
    }
    set {
        // custom setter
    }
}

Leads to this generated header:

SWIFT_CLASS("_TtC11SwiftToObjC9TestClass")
@interface TestClass : NSObject
@property (nonatomic, getter=isOpen) BOOL open;
- (nonnull instancetype)init OBJC_DESIGNATED_INITIALIZER;
@end