Swift Arrays of Multiple Types

Question

I'm working to convert an iOS Obj-C project to Swift a class at a time. One Obj-C class involved the creation of an NSArray with even elements descriptive NSStrings and odd elements NSNumbers. Not a great piece of design in retrospect but perfectly valid and it did the job. I've converted this to Swift:

let coins = ["1p", 0.01 , "2p" , 0.02 , "5p" , 0.05 , "10p" , 0.10 , "20p" , 0.20 , "50p" , 0.50 , "99p" , 0.99 ,  "£1" , 1.00 ,  "£2" , 2.00 , "£5" , 5.00 , "£9.99" , 9.99 , "£10" , 10.00 , "£20" , 20.00]

I do realise that Swift enforces a single type in a one-dimensional array, so we wouldn't so much be talking an array of multiple types as an array of a flexible type - I expected it would infer AnyObject.

I never got to find out however, because it seems this line is an Xcode killer. In my overall project it causes indexing to hang, quickly becoming unresponsive and eventually consuming all system memory. Even this single line of code pasted into the init of a UIView subclass added to a blank single view application causes Xcode to hang on attempting to build in a similar fashion (i'm curious if others have the same experience).

Is there any legitimacy to what i'm attempting here, given that it is compilable code. If so, have I stumbled upon a Swift bug, or perhaps failed to do something vital to allow this to work. I can obviously find a far better way to go about doing what I want, particularly in Swift, but I don't think arrays of multiple types are so rarely seen in Obj-C that this isn't worth understanding further.

What happens if you change to let coins : AnyObject[] = ["1p", 0.01, ... ? — Léo Natan
– Léo Natan, Commented Jun 13, 2014 at 19:25
The way you have it written, it looks more like a dictionary than an array. Have you tried writing it as a dictionary with either the string or the number as the key, depending on how you are going to use it. — JScarry
– JScarry, Commented Jun 13, 2014 at 19:37
Heh I get the same thing. When I add this line to my playground, I see kernel_task spike up to 10gb in memory usage. Once I force quit Xcode, it drops back down to it's more normal 1.4gb. I tried let coins: AnyObject[] and let coins: Array<AnyObject>. — johnboiles
– johnboiles, Commented Jun 13, 2014 at 19:44
sure AnyObject is the right type? shouldnt that be Any? Array<Any>.convertFromArrayLiteral(1,1.2,"x") — Christian Dietrich
– Christian Dietrich, Commented Jun 13, 2014 at 19:51
I agree it should be Any, but I'm not sure if that should compile at all due to Swift's strict type nature — Jack
– Jack, Commented Jun 13, 2014 at 19:56

johnboiles · Accepted Answer · 2014-06-13 19:53:12Z

2

Looks like you've run into a bug in Xcode/Swift with Array<AnyObject> and literals. I get the same result. Seems to get exponentially worse the more elements I add (my RAM gets full after ~6 elements). As a workaround, it seems to work fine to create a mutable array (using var instead of let) and adding the elements one by one. Janky without a doubt, but it doesn't crash Xcode.

var coins: Array<AnyObject> = []
coins += "1p"
coins += 0.01
coins += "2p"
coins += 0.02
coins += "5p"
coins += 0.05
coins += "10p"
coins += 0.10
coins += "20p"
coins += 0.20
coins += "50p"
coins += 0.50
coins += "99p"
coins += 0.99
coins += "£1"
coins += 1.00
coins += "£2"
coins += 2.00
coins += "£5"
coins += 5.00
coins += "£9.99"
coins += 9.99
coins += "£10"
coins += 10.00
coins += "£20"
coins += 20.00

answered Jun 13, 2014 at 19:53

johnboiles

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Comments

Christian Dietrich · Accepted Answer · 2014-06-13 20:05:26Z

1

Since e.g. Int is a struct instance and not an class instance the type is Any[]

var x : Any[] = [1,"2",3.0]

answered Jun 13, 2014 at 20:05

Christian Dietrich

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2 Comments

Tom Hawley Over a year ago

Agree entirely it should be, although when I inspected the individual elements I seem to recall them being derivative of NSString and NSNumber. Perhaps Swift won't yet correctly infer a collection of mixed value types in an array?

Christian Dietrich Over a year ago

the problem may be that swift does strange autoconversion between NSString and String and that may fail in this case.

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