Delete Objects From Parse/ Cannot cast to PFObject/ NSArrayM

Question

My problem is: I am querying user["key"] that I am attempting to assign to a new variable, as on the documentation.

The column in Parse is an array of Strings, in my query, if I println(user["key"]) it returns the correct objects.

However, when I do:

let myVariable = user["key"] as String

or

let myVariable = user["key"] as! String

I have the error:

Could not cast a value of type _NSArrayM to NSString

My end goal is to retrieve objects from Parse, and submit an "if" condition and then delete the results. For this I need to convert the objects into PFObject and this is where I struggle.

To add, I can only downcast to AnyObject! from let myVariable = user["key"]

and when I try to delete this object, I have the error

NSArrayM delete: unrecognised selector sent to instance.

Any help would be greatly appreciated.

First you say "The column in Parse is an array of Strings", then you try as String, what a surprise that is not working, you should maybe use [String] — luk2302
– luk2302, Commented Jun 20, 2015 at 11:32
Indeed, Thanks a lot. I got confused as my objects in Parse were themselves arrays. I do admit that the mistake was silly. Thanks again for your response. — viktor
– viktor, Commented Jun 21, 2015 at 11:04

Icaro · Accepted Answer · 2015-06-20 12:52:12Z

1

Parse.com normally return an array, as you can see in your error message:

Could not cast a value of type _NSArrayM to NSString

__NSArrayM is a code-word for a mutable array, so you are trying to cast an array to a string.

If you are sure your query is return just one result you can retrieve just the last (and only) element in the array and cast to string.

if let myVariable = user["key"].last as? String{
    println("myVariable key is \(myVariable)"
} else { 
    println("Could not retrieve key") 
}

edited Jun 20, 2015 at 12:52

answered Jun 20, 2015 at 11:45

Icaro

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6 Comments

nhgrif Over a year ago

I think you have an extra ?. I don't have Xcode open... but shouldn't it just be user["key"].last as? String?

Icaro Over a year ago

@nhgrif You are correct, I was thinking because the array could be empty it would be an optional but I test in XCode and the compiler ask me to delete. I already fix the code above. Thanks

nhgrif Over a year ago

You are correct. The array could be empty and last could return nil, but the ? is unnecessary here anyway.

Icaro Over a year ago

@viktor I am glad that helped you, please don't forget to check the issue as solved if it is fixed now, and good luck with your app!

viktor Over a year ago

@Icaro, everything solved and fine. Aside this slight mistake, I actually had the identical column in Parse being constantly added with objects as I was trying to modify them. I therefore had to stop the addition of objects before applying the modification. And while trying a considerable number of solutions without having actually identify the exact source of my problem, I got lost in the casting of my objects and so on. I had to take a good step back from the project, a bit of sleep and a game of tennis, and then fresh mind good to go. But thanks a million for your help and for the wishes.

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