Swift HStack 视图不符合协议“视图”

Question

I have built this code

struct StarDifficultyView: View {

var numberOfStarsToShow: Int
var numberOfTotalStarsToShow: Int = 5

var body: some View {
    HStack{
        var numberLeftToShow = numberOfStarsToShow
        ForEach(1..<numberOfTotalStarsToShow+1){_ in
            if(numberLeftToShow > 0){
                Image(systemName: "star.fill")
                    .foregroundColor(Color.yellow)
                numberLeftToShow -= 1
            }else{
                Image(systemName: "star.fille")
                    .foregroundColor(Color.yellow)
            }
        }
    }
}

}

It gives me an error on the line if(numberLeftToShow > 0){ saying "Type '()' cannot conform to 'View'"

Can anyone tell me what I'm doing wrong

Answer 1

Don't throw away the closure parameter for the ForEach !

var body: some View {
    HStack{
        ForEach(0..<numberOfTotalStarsToShow){ i in // don't ignore the "i" here by writing "_"

            // "i" will be different in each "iteration"
            // use that to figure out which image to show
            if(i < numberOfStarsToShow){
                Image(systemName: "star.fill")
                    .foregroundColor(Color.yellow)
            } else {
                Image(systemName: "star")
                    .foregroundColor(Color.yellow)
            }
        }
    }
}

Answer 2

Never mind, I just did this

struct StarDifficultyView: View {

    var numberOfStarsToShow: Int
    var numberOfTotalStarsToShow: Int = 5

    var body: some View {
        HStack{
            ForEach(1..<numberOfStarsToShow+1){_ in
                Image(systemName: "star.fill")
                    .foregroundColor(Color.yellow)
            }
            ForEach(1..<numberOfTotalStarsToShow-numberOfStarsToShow+1){_ in
                Image(systemName: "star.fill")
                    .foregroundColor(Color.gray)
                    .opacity(0.7)
            }
        }
    }
}

Basically, it just loops through the number of yellow stars to show and then works out how many grey ones to show and does another ForEach to display the leftover ones needed

Answer 3

Explaining the issue:

You should not add expressions inside the view builder. So numberLeftToShow -= 1 will throw and error because it returns a void ('aka' type()) and this does not conform to View ! that is the exact reason for the compiler!

Note 1

Don't use SwiftUI like the UIKit! SwiftUI views may execute over time on any state change and should not be used for calculating anything in this way

Note 2

You can convert 1..<numberOfTotalStarsToShow+1 to a closed range like 1...numberOfTotalStarsToShow

Note 3

Try not to use branch and convert your if/else code to something like:

Image(systemName: numberLeftToShow > 0 ? "star.fill" : "star.fille")
    .foregroundColor(Color.yellow)

Note 4:

The lower bound of a range can not be less than the upper range, but you can iterate over a reversed range like:

(1...numberOfTotalStarsToShow).reversed()

Note 5:

try use a single source of truth like the forEach parameter itself!

Final Result:

    var body: some View {
        HStack {
            ForEach((1...numberOfTotalStarsToShow).reversed(), id:\.self) { i in
                Image(systemName:  i > 0 ? "star.fill" : "star.fille")
                    .foregroundColor(Color.yellow)
            }
        }
    }