Dynamic Height of Rectangle as from text content in SwiftUI

From what I understood of your question is that:

1. You have an HStack in which the leftmost view is a Rectangle and the rightmost view is a Text.
2. You want the Rectangle to be the same height as the Text.

The problem is that the height of the HStack is based on the tallest child view which happens to be the Rectangle but a Rectangle view does not have any intrinsic size like Text and will occupy all the space the parent provides, or if you manually apply a frame.
You set a width of 20 but leave height and so it takes the entire height it can get.

This indicates that we need to set the height of the Rectangle to be same as the dynamic Text but the problem is that we don't know the height upfront.

To solve this:

1. First we need to know the height of the dynamic Text.
   • For this we will use GeometryReader and access the height value.
2. The height is in a child view so we need it to notify the parent it's height value.
   • For this we will use PreferenceKey
3. The parent view should update the Rectangle when it gets to know the Text height
   • A simple @State variable will suffice now

Solution:

struct ContentLengthPreference: PreferenceKey {
   static var defaultValue: CGFloat { 0 }
   
   static func reduce(value: inout CGFloat, nextValue: () -> CGFloat) {
      value = nextValue()
   }
}

struct ContentView: View {
   @State var textHeight: CGFloat = 0 // <-- this
   
   var body: some View {
      HStack {
        Rectangle()
           .frame(width: 20, height: textHeight) // <-- this
        
        Text(String(repeating: "lorem ipsum ", count: 25))
           .overlay(
              GeometryReader { proxy in
                Color
                   .clear
                   .preference(key: ContentLengthPreference.self,
                               value: proxy.size.height) // <-- this
              }
           )
      }
      .onPreferenceChange(ContentLengthPreference.self) { value in // <-- this
        DispatchQueue.main.async {
           self.textHeight = value
        }
      }
   }
}

1. Create ContentLengthPreference as our PreferenceKey implementation
2. on Text; Apply overlay containing GeometryReader
3. overlay will have same height as Text
4. in GeometryReader, Color.clear is just a filler invisible view
5. anchorPreference modifier allows us to access and store height
6. onPreferenceChange modifier on parent HStack can catch the value passed by child view
7. parent saves the height to a state property textHeight
8. textHeight can be applied on Rectangle and will update the view when this value updates

_{Credits: https://www.wooji-juice.com/blog/stupid-swiftui-tricks-equal-sizes.html}

Output (including your header + footer views):

EDIT:

If you have multiple of these in a List then you don't need to do anything. Each row will size automatically upto the Text height.
It's free!!!

struct ContentView: View {
   var body: some View {
      List(0..<20) { _ in
        ArticleView()
      }
   }
}

struct ArticleView: View {
   var body: some View {
      VStack(alignment: .leading) {
        HStack {
           Circle()
              .fill(Color.blue)
              .frame(width: 15, height: 15)
              .overlay(Circle().inset(by: 2).fill(Color.white))
           
           Text("Headline").font(.headline)
        }
        
        HStack {
           Rectangle().frame(width: 20)
           
           Text(String(repeating: "lorem ipsum ", count: (5...50).randomElement()!))
        }
        
        HStack {
           Circle()
              .fill(Color.orange)
              .frame(width: 15, height: 15)
              .overlay(Circle().inset(by: 2).fill(Color.white))
           
           Text("Footer").font(.subheadline)
        }
      }
   }
}

You can add max-height like this

HStack {
    VStack {
        //                    Text("l").padding(.leading,5)
        //                    Text("l").padding(.leading,5)
        Rectangle().frame(width: 20)
    }
    
    Text("Time Line Content Time Line Content Time Line Content Time Line Content fdfgfuysdgfuydsgfgds fgfyusdfyfdsdfsdfgyusdg fydsufidsfy uyfudsfuydsufysdfsdf dfusdtfoisdtftdsoftsdftsydtfsdtfodstfdstf fgdsygfdsgfuygu").font(.caption)
}.frame(minHeight: 0, maxHeight: .infinity) //<---here

Or Set up your cell view like this

struct ContentCellView: View {
    var isLast: Bool = false
    var body: some View {
        HStack(alignment: .top, spacing: 0) {
            VStack(alignment: .leading) {
                Image(systemName: "message.circle").frame(width: 30)
                if !isLast {
                    Rectangle().fill(Color.black).frame(width: 1).padding(.leading, 15.5)
                }
            }
            Text("Time Line Content Time Line Content Time Line Content Time Line Content fdfgfuysdgfuydsgfgds fgfyusdfyfdsdfsdfgyusdg fydsufidsfy uyfudsfuydsufysdfsdf dfusdtfoisdtftdsoftsdftsydtfsdtfodstfdstf fgdsygfdsgfuygu")
        }.frame(minHeight: 0, maxHeight: .infinity)
    }
}

struct ContentViewList: View {
    var body: some View {
        ScrollView{
            VStack(spacing: 0){
                ForEach((1...10).reversed(), id: \.self) {
                    ContentCellView(isLast: $0 == 1) // isLast for not showing last line in last cell
                }
            }
        }.padding()
    }
}

This is what i did

HStack {
          Text("some long text........")
               .font(.body)
               .padding(.horizontal, 20)
        }
        .overlay(
            GeometryReader { proxy in
                Rectangle()
                    .frame(width: 20, height: proxy.size.height)
            }
        )