I want to insert an optional in an array as follows
let arr: AnyObject[] = [1, 2, nil, 4, 5]
The following expression throws a compile error saying
Cannot convert the expression's type 'AnyObject[]' to type 'AnyObject'
How can I made this work? I need optional or nil value in the array even though I know I shouldn't.
If you're just going to be inserting either Ints or nils, use
Swift < 2.0
var arr: Int?[] = [1, 2, nil, 4, 5]
Swift >= 2.0
var arr: [Int?] = [1, 2, nil, 4, 5]
Swift 3x
var arr: Array<Int?> = [1, 2, nil, 4, 5]
This can be done for any type (not just Int; that is if you want an array to hold a specific type but allow it to be empty in some indices, like say a carton of eggs.)
Just like this:
let arr: AnyObject?[] = [1, 2, nil, 4, 5]
it makes the Array of type AnyObject?
You can't use AnyObject:
18> let ar : AnyObject?[] = [1, 2, nil, 4, 5]
<REPL>:18:25: error: cannot convert the expression's type 'AnyObject?[]' to type 'AnyObject?'
let ar : AnyObject?[] = [1, 2, nil, 4, 5]
^~~~~~~~~~~~~~~~~
But you can use Any:
18> let ar : Any?[] = [1, 2, nil, 4, 5]
ar: Any?[] = size=5 {
[0] = Some {
Some = <read memory from 0x7f8d4b841dc0 failed (0 of 8 bytes read)>
}
[1] = Some {
Some = <read memory from 0x7f8d50da03c0 failed (0 of 8 bytes read)>
}
[2] = Some {
Some = nil
}
[3] = Some {
Some = <read memory from 0x7f8d4be77160 failed (0 of 8 bytes read)>
}
[4] = Some {
Some = <read memory from 0x7f8d4be88480 failed (0 of 8 bytes read)>
}
}
The Apple documentation makes this clear:
“Swift provides two special type aliases for working with non-specific types:
o AnyObject can represent an instance of any class type.
o Any can represent an instance of any type at all, apart from function types.”Excerpt From: Apple Inc. “The Swift Programming Language.” iBooks. https://itun.es/us/jEUH0.l
It appears that Int and probably other primitive types are not subtypes of a class type and thus AnyObject won't work.
let ar: AnyObject[] = [1,2,nil,3] is illegal because nil is not convertible to AnyObject.
let a: AnyObject?[] = [1,3,nil,2] or let a: Int?[] = [1,3,nil,2] works.
If you need an Objective-C bridgeable Array use
let a: AnyObject[] = [1, 2, NSNull(), 4, 5]
It's a cheat, but if you're using the nil as a sentinel it might be advisable to just use Tuples, one element being a Bool to rep the validity of the second.
var arr = [(true, 1), (true, 2) , (false, 0) , (true, 4),(true,5)]
