【SwiftUI】カスタム ViewModifier の使い方と使いどころ 🤔 👉 https://android.benigumo.com/20240221/custom-viewmodifier/

CustomViewModifier.swift

import SwiftUI

struct TestView: View {
  var body: some View {

    VStack {
      Text("top")
      Text("bottom")
    }

    VStack {
      Text("top")
      Text("bottom")
    }
    .modifier(TitleTextFormat())

    VStack {
      Text("top")
      Text("bottom")
    }
    .titleTextFormat()

    VStack {
      Text("top")
      Text("bottom")
    }
    .titleTextFormat2()

    TitleTextFormatView {
      VStack {
        Text("top")
        Text("bottom")
      }
    }

    TitleTextFormatView {
      Text("top")
      Text("bottom")
    }
  }
}

struct TitleTextFormat: ViewModifier {
  func body(content: Content) -> some View {
    content
      .font(.title)
      .foregroundColor(.red)
  }
}

extension View {
  func titleTextFormat() -> some View {
    modifier(TitleTextFormat())
  }
}

extension View {
  func titleTextFormat2() -> some View {
    self
      .font(.title)
      .foregroundColor(.red)
  }
}

struct TitleTextFormatView<Content: View>: View {
  @ViewBuilder var content: Content

  var body: some View {
    content
      .font(.title)
      .foregroundColor(.red)
  }
}

#Preview {
  TestView()
}