ForEach loop keeps giving me an error

Can you show full code which gives you such errors.

@OOPer

Code Block 
import SwiftUI
struct ContentView: View {
	
	@State private var showingSheet = false
	
    var body: some View {
		ZStack{
			VStack{
				Text("Reference Buddy :D")
					.font(.title)
					.fontWeight(.bold)
				HStack{
					Button("Physics") {
						self.showingSheet.toggle()
					}
					.sheet(isPresented: $showingSheet) {
						physicsPage()
					}
					Button("Trigonometry", action: {})
					Button("Calculus", action: {})
				}
				HStack{
					Button("Pre-calculus", action: {})
					Button("Geometry", action: {})
					Button("Statistics", action: {})
				}
				HStack{
					Button("Chemistry", action: {})
					Button("Biology", action: {})
					Button("Astronomy", action: {})
				}
			}
		}
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
struct physicsPage: View {
	@Environment(\.presentationMode) var presentationMode
	var body: some View {
		VStack{
			Text("Did you know that...")
			ForEach((1...10), id: \.self) {
					Text("\($showingSheet)")
				}
			Button("Back") {
				self.presentationMode.wrappedValue.dismiss()
			}
		}
	}
}

You need to replace by:

Code Block 
            ForEach(1...10, id: \.self) {_ in 

I remember seeing on the forum a crash problem with ForEach, but impossible to search for it on this forum !

But Google found it !!! https://developer.apple.com/forums/thread/660718

Thanks for showing your code. But in your physicsPage, the identifier $showingSheet (or showingSheet) is obviously not visible.
You may need to fix it first. (There are some other points to fix.)

To make an example, I have modified your code as follows:

Code Block 
import SwiftUI
struct ContentView: View {
    
    @State private var showingSheet = false
    
    var body: some View {
        ZStack{
            VStack{
                Text("Reference Buddy :D")
                    .font(.title)
                    .fontWeight(.bold)
                HStack{
                    Button("Physics") {
                        self.showingSheet.toggle()
                    }
                    .sheet(isPresented: $showingSheet) {
                        PhysicsPage(showingSheet: $showingSheet) //<-
                    }
                    Button("Trigonometry", action: {})
                    Button("Calculus", action: {})
                }
                HStack{
                    Button("Pre-calculus", action: {})
                    Button("Geometry", action: {})
                    Button("Statistics", action: {})
                }
                HStack{
                    Button("Chemistry", action: {})
                    Button("Biology", action: {})
                    Button("Astronomy", action: {})
                }
            }
        }
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
struct PhysicsPage: View {
    @Environment(\.presentationMode) var presentationMode
    @Binding var showingSheet: Bool //<-
    var body: some View {
        VStack{
            Text("Did you know that...")
            ForEach((1...10), id: \.self) {
                Text("\($showingSheet)")
            }
            Button("Back") {
                self.presentationMode.wrappedValue.dismiss()
            }
        }
    }
}

This code generates 5 errors with Xcode 12.0.1.

Code Block 
 Extra arguments at positions #2, #3 in call
 Missing argument for parameter 'content' in call
 Cannot convert value of type 'ClosedRange<Int>' to expected argument type 'Range<Int>'
 Generic parameter 'Content' could not be inferred
 Cannot infer key path type from context; consider explicitly specifying a root type

As you have shown in your original post.

The most important I think is your #1:

Code Block 
1.  "Cannot convert value of type 'ClosedRange<Int>' to expected argument type 'Range<Int>'

In the SwiftUI struct ForEach, there is no initializer taking ClosedRange<Int> (generated with operator ...), but there is one taking Range<Int> (generated with ..<).
ForEach
init(Range<Int>, content: (Int) -> Content)

The initializer takes Range<Int> and has no parameter named id:.

With using it:

Code Block 
struct PhysicsPage: View {
    @Environment(\.presentationMode) var presentationMode
    @Binding var showingSheet: Bool //<-
    var body: some View {
        VStack{
            Text("Did you know that...")
            ForEach(0..<10) {_ in //<-
                Text("\($showingSheet)")
            }
            Button("Back") {
                self.presentationMode.wrappedValue.dismiss()
            }
        }
    }
}

This code still generates one error, but it is more understandable than the former five errors (at least, for me):

Code Block 
Instance method 'appendInterpolation' requires that 'Binding<Bool>' conform to '_FormatSpecifiable'

In the String Interpolation passed to the first argument of Text, only some limited types are usable.
If you do not know about the types available, you should better use String:

Code Block 
struct PhysicsPage: View {
    @Environment(\.presentationMode) var presentationMode
    @Binding var showingSheet: Bool //<-
    var body: some View {
        VStack{
            Text("Did you know that...")
            ForEach(0..<10) {_ in //<-
                Text("\(String(describing: $showingSheet))") //<-
            }
            Button("Back") {
                self.presentationMode.wrappedValue.dismiss()
            }
        }
    }
}

Your actual code may be a little different than you have shown, but I think you can fix all errors following the fixes I have shown here.

@OOPer

But

Code Block 
ForEach((1...10), id: \.self) {

works

@Claude31 

But ... works

A fragment of code does not make sense. It may work with other parts fixed properly.

Just that it is hard to find where to fix.

In the SwiftUI struct ForEach, there is no initializer taking ClosedRange<Int> (generated with operator ...), but there is one taking Range<Int> (generated with ..<).
ForEach
init(Range<Int>, content: (Int) -> Content)
The initializer takes Range<Int> and has no parameter named id:.

The full fragment is:

Code Block 
ForEach(1...10, id: \.self) {
					Text("\($0)")
				}

It works with a closed Range.

But this

Code Block 
ForEach(1...10) {
					Text("\($0)")
				}

causes a compiler error.

Did I miss something ?

@OOPer, thank you so much. I found a fix.

Code Block 
ForEach((1...10), id: \.self) {					
	Text("\($showingSheet)")		
}

This doesn't work because showSheet is not in the same struct and also private.

After reading your answer, I changed my code to this:

Code Block 
ForEach(0..<10) {_ in
				Text("Hello")
						}

The _ in part is required. If I remove that, I'l get an Contextual type for closure argument list expects 1 argument, which cannot be implicitly ignored error.

If I changed (0..<10) to (0...10), I get this error:
Cannot convert value of type 'ClosedRange<Int>' to expected argument type 'Range<Int>'

Thank you so much :D

@TurtleLover

 thank you so much. I found a fix. 

You are welcome.
Seems you have found how to fix your code for some types of error messages.

But, please remember, the Swift compiler is not good at generating proper diagnostics especially when compiling SwiftUI views.
If you are unlucky, any of the error messages might not be pointing the right place to fix.

When you find some cases that you cannot fix by yourself, please do not hesitate to share your experience.
New questions will also be welcome.