Compile error, doing calculations in View body

Question

Hi,

I'm trying to show a number of buttons of a certain relative size to the screen width. For now I'm hard-coding the number of buttons, just to get the collection view wrap style working.

I'm getting the Xcode error:

The compiler is unable to type-check this expression in reasonable time

It seems obvious that doing the indexing calculations probably cause the problem. But I don't know how to do that calculation once per iteration, and store the value.

It worked fine, compiled, and ran in preview mode a couple of times. Then with no changes it just stopped compiling, and Xcode gave the error.

Any suggestions as to what can I do? Eventually I want to use the index calculation to subscript an array value.

Code Block struct collectionView: View {
    let totalElements = 5
    let rowCount = 2
    let rowLength = 3
    var body: some View {
        GeometryReader<AnyView> { geometry in
            return AnyView(
                VStack(alignment: .leading) {
                    ForEach(0..<self.rowCount) { rowIndex in
                        HStack {
                            ForEach(0..<self.rowLength) { elementIndex in
                                if ((rowIndex * self.rowLength) + elementIndex < self.totalElements) {
                                    Button(action: {
                                        print(msg: "\((rowIndex * self.rowLength) + elementIndex)")
                                    }) {
                                        Text("\( (rowIndex * self.rowLength) + elementIndex)")
                                    }
                                    .background(Color.purple)
                                    .foregroundColor(Color.white)
                                }
                            } // ForEach elementIndex
                        } // HStack
                    } // ForEach rowIndex
                } // VStack
            ) // AnyView
        } // GeometryReader
    }
}

SwiftUI

354

Posted by

FarOeuf

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Answer 1

hi,

two things on syntax will make this compile (Xcode 11.6):

line 16: remove the msg: label ... there is no label for print().
lines 20-21: move these as modifiers onto the Text in line 18, inside the closing brace on line 19.

hope that helps,
DMG

Posted by

DelawareMathGuy

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Answer 2

hi,

two things on syntax will make this compile (Xcode 11.6):

line 16: remove the msg: label ... there is no label for print().
lines 20-21: move these as modifiers onto the Text in line 18, inside the closing brace on line 19.

hope that helps,
DMG

Posted by

DelawareMathGuy

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Answer 3

Ach, my obvious mistake on the first one. I had been using a separate custom log method, which did have a label.

On the second, ahh yes I see. Compiled first time with the changes.

thanks very much,

Posted by

FarOeuf

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Answer 4

For anyone happening upon this, here's the working version. In my case I'm drawing a collection of buttons.

Code Block struct collectionView: View {
    let totalElements = 8
    let elementWidth: CGFloat = 80.0
    var body: some View {
        GeometryReader<AnyView> { geometry in
            let elementsPerRow = Int(geometry.size.width / self.elementWidth)
            let rowCount = Int( (CGFloat(self.totalElements) / CGFloat(elementsPerRow)).rounded(.up) )
            return AnyView(
                VStack(alignment: .leading) {
                    ForEach(0..<rowCount) { rowIndex in
                        HStack {
                            ForEach(0..<elementsPerRow) { elementIndex in
                                if ((rowIndex * elementsPerRow) + elementIndex < self.totalElements) {
                                    Button(action: {
                                        print("\((rowIndex * elementsPerRow) + elementIndex)")
                                    }) {
                                        Text("\( (rowIndex * elementsPerRow) + elementIndex)")
                                        .frame(maxWidth: self.elementWidth, maxHeight: self.elementWidth)
                                        .background(Color.purple)
                                        .foregroundColor(Color.white)
                                        .clipShape(Circle())
                                    }
                                }
                            }
                        }
                    }
                }
            )
        }
    }
}

Posted by

FarOeuf

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Compile error, doing calculations in View body

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