Swift array of nested struct type (count, repeatedValue)

Question

Relatively new to Swift and struggling with the simplest of things. I wish to preallocate an array of structs set to default values. This works just as long as the struct is not nested inside another type. Any ideas? Here is simplified example:

struct PlainStruct
{
    var yo:Float = 0.0
}

class WrapperClass
{
    struct NestedStruct
    {
        var yo:Float = 0.0
    }
}

// Works just fine
var a = [PlainStruct](count:2, repeatedValue:PlainStruct())

// Error - Cannot call value of non-function type '[WrapperClass.NestedStruct.Type]'
var b = [WrapperClass.NestedStruct](count:2, repeatedValue:WrapperClass.NestedStruct())

Thanks

It seems to be a compiler bug: stackoverflow.com/questions/25682113/… — giorashc
– giorashc, Commented Nov 19, 2015 at 12:27
Hi, yeah good point, but in this case I actually do want a Float and without that I believe it defaults to a Double. Thanks — greekgoddj
– greekgoddj, Commented Nov 19, 2015 at 12:28

Eric Aya · Accepted Answer · 2015-11-19 12:26:52Z

4

It works if you create a typealias. Example:

struct PlainStruct
{
    var yo:Float = 0.0
}

class WrapperClass
{
    struct NestedStruct
    {
        var yo:Float = 0.0
    }
}

typealias Nested = WrapperClass.NestedStruct

var b = [Nested](count:2, repeatedValue:WrapperClass.NestedStruct())

As for why we have to do this... I don't like to say this without proof but I think it's a compiler bug, I believe we should be able to use your original version.

answered Nov 19, 2015 at 12:26

Eric Aya

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2 Comments

greekgoddj Over a year ago

Nice, didn't know about type alias. That does work so will go with that until the bug in the compiler is addressed. Thanks!

nstein Over a year ago

Problem still appears in Swift 3.0.2. Array<WrapperClass.NestedStruct>(repeating: ..., count: ...) works around the problem as well.

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