Exc_bad_access on BOOL Getter in swift

Question

I want to make some operations when boolean values of property goes true to false and false to true.
I've set the getter setter for that, so I can do those operations on setter of boolean property.

But always crashes with EXC_BAD_ACCESS code = 2, can anyone help me to understand this what's wrong I'm doing here.

var reportActivityStarted:Bool {
        set {
            if self.reportActivityStarted {
                //Operations when boolean is true
            }else{
                //Operations when boolean is false
            }
        }
        get{
            return self.reportActivityStarted
        }
    }

When I changes it's boolean value, it crashes at get{

self.reportActivityStarted = true

Inside set, you should refer the value using the 'newValue' and should not access self.reportActivityStarted. — Shripada, Feb 11 '16 at 09:06
@Martin R - can I know where you found this question in stackoverflow. as I searched for it, but didn't found relevant. — Kiran Jasvanee, Feb 11 '16 at 09:42
Type `[swift] EXC_BAD_ACCESS get set` into the search field, it is among the result list. — Martin R, Feb 11 '16 at 09:45
@Martin R - the link you have given it's recursive. I'm not changing the boolean value on setter. check the link you have provided and let me know how you think it's dublicate — Kiran Jasvanee, Feb 11 '16 at 09:46
Your setter calls the getter method, and the getter calls itself recursively. It is the same issue. — Martin R, Feb 11 '16 at 09:47
I clearly mention that I'm getting **[swift] EXC_BAD_ACCESS** on **get{** — Kiran Jasvanee, Feb 11 '16 at 09:47
@Martin R - Look at that question's answer, it's calling the setter from within the setter. — Kiran Jasvanee, Feb 11 '16 at 09:49
@Martin R - I'm not anyway setting the boolean in my setter. is it looks like that in my question.? — Kiran Jasvanee, Feb 11 '16 at 09:50
In your setter method you call `if self.reportActivityStarted`. That calls the getter method!! And the getter method calls itself recursively. It is really the same issue: `get` or `set` in a computed property must not call itself. The solution is to use property observers, as in the referenced Q&A. — Martin R, Feb 11 '16 at 09:52
And btw, just look at the stack backtrace when the exception occurs: You should *see* the recursion. — Martin R, Feb 11 '16 at 09:55
@Martin R - Okay. I thought my case is different, I understand now. I already checked that question's answer and it was mention that he called the setter from within the setter, so misunderstood the case and thought might be different. Thanks :). — Kiran Jasvanee, Feb 11 '16 at 10:04

score 3 · Accepted Answer · answered Feb 11 '16 at 09:14

As already noted by @Unheilig you are generating an infinite recursive call. Infact the getter of reportActivityStarted is recursively invoking itself.

If you want to run some logic when a property is set or retrieved then you should use a property observer like this:

var reportActivityStarted: Bool {
    willSet(newValue) {
        switch reportActivityStarted {
        case true: print("reportActivityStarted is true before assignment") // <- your logic goes here
        case false: print("reportActivityStarted is false before assignment") // <- your logic goes here
        }
    }
}

@Unheilig: No, I think you should undelete your answer. It did explain how to create a private variable for this scenario. It's a different approach and it would be nice having it explained here. — Luca Angeletti, Feb 11 '16 at 10:26

score 0 · Answer 2 · answered Feb 11 '16 at 09:10

if you want to use get, set you may need to have another variable to save the value on it in set and request it in get. like this:

var _reportActivityStarted = false 
var reportActivityStarted:Bool {
        set {
             _reportActivityStarted = newValue
            if _reportActivityStarted {
                //Operations when boolean is true
            }else{
                //Operations when boolean is false
            }
        }
    get{
        return _reportActivityStarted
    }
}

But from what I see in you code sample you don't need set and get at all. you just need to use didSet instead. like this

var reportActivityStarted:Bool {
            didSet {
            if reportActivityStarted {
                //Operations when boolean is true
            }else{
                //Operations when boolean is false
            }
        }
}

Exc_bad_access on BOOL Getter in swift

2 Answers2