SwiftUI iOS 15 button design system

swiftui-ios15-button-design-system.swift

//
//  ContentView.swift
//  SwiftUIDemo
//
//  Created by Damir Stuhec on 07/10/2021.
//

import SwiftUI

// MARK: - CustomButtonStyle

struct CustomButtonStyle: PrimitiveButtonStyle {
    enum `Type` {
        case plain(customTint: Color?)
        case bordered(customTint: Color?)
        case prominent(customBackground: Color?, customForeground: Color?)

        var tint: Color? {
            switch self {
            case .plain(let customTint), .bordered(let customTint), .prominent(let customTint, _):
                return customTint
            }
        }

        var foreground: Color? {
            switch self {
            case .plain, .bordered:
                return nil
            case .prominent(_, let customForeground):
                return customForeground
            }
        }
    }

    var type: Type
    var size: ControlSize = .regular
    var isDisabled = false
    var isLoading = false
    var scaleWidthToFill = false

    @ViewBuilder
    func makeBody(configuration: PrimitiveButtonStyle.Configuration) -> some View {
        switch type {
        case .plain:
            _ButtonBuilderView(
                configuration: configuration,
                size: size,
                isDisabled: isDisabled,
                isLoading: isLoading,
                scaleWidthToFill: scaleWidthToFill
            )
            .buttonStyle(.borderless)
            .tint(shouldIgnoreCustomColors(configuration: configuration) ? nil : type.tint)

        case .bordered:
            _ButtonBuilderView(
                configuration: configuration,
                size: size,
                isDisabled: isDisabled,
                isLoading: isLoading,
                scaleWidthToFill: scaleWidthToFill
            )
            .buttonStyle(.bordered)
            .tint(shouldIgnoreCustomColors(configuration: configuration) ? nil : type.tint)

        case .prominent:
            _ButtonBuilderView(
                configuration: configuration,
                size: size,
                isDisabled: isDisabled,
                isLoading: isLoading,
                scaleWidthToFill: scaleWidthToFill
            )
            .buttonStyle(.borderedProminent)
            .tint(shouldIgnoreCustomColors(configuration: configuration) ? nil : type.tint)
            .foregroundColor(shouldIgnoreCustomColors(configuration: configuration) ? nil : type.foreground)
        }
    }

    private func shouldIgnoreCustomColors(configuration: PrimitiveButtonStyle.Configuration) -> Bool {
        configuration.role != nil || isDisabled || isLoading
    }

    private struct _ButtonBuilderView: View {
        let configuration: PrimitiveButtonStyle.Configuration
        let size: ControlSize
        let isDisabled: Bool
        let isLoading: Bool
        let scaleWidthToFill: Bool

        private var font: Font? {
            switch size {
            case .mini:
                return .subheadline.weight(.regular)
            case .small:
                return .subheadline.weight(.regular)
            case .regular:
                return .body.weight(.medium)
            case .large:
                return .body.weight(.semibold)
            @unknown default:
                return nil
            }
        }

        var body: some View {
            Button(
                role: configuration.role,
                action: configuration.trigger,
                label: {
                    configuration.label
                        .font(font)
                        .opacity(isLoading ? 0 : 1)
                        .overlay {
                            if isLoading {
                                ProgressView()
                            }
                        }
                        .frame(maxWidth: scaleWidthToFill ? .infinity : nil)
                }
            )
            .disabled(isDisabled || isLoading)
            .controlSize(size)
        }
    }
}

// MARK: - Examples of defining prebuilt button styles using the CustomButtonStyle

extension PrimitiveButtonStyle where Self == CustomButtonStyle {
    static func primary(size: ControlSize = .large, isDisabled: Bool = false, isLoading: Bool = false, scaleWidthToFill: Bool = true) -> CustomButtonStyle {
        .init(
            type: .prominent(customBackground: .yellow, customForeground: .black),
            size: size,
            isDisabled: isDisabled,
            isLoading: isLoading,
            scaleWidthToFill: scaleWidthToFill
        )
    }

    static func secondary(size: ControlSize = .large, isDisabled: Bool = false, isLoading: Bool = false, scaleWidthToFill: Bool = true) -> CustomButtonStyle {
        .init(
            type: .prominent(customBackground: Color(.secondarySystemFill), customForeground: .primary),
            size: size,
            isDisabled: isDisabled,
            isLoading: isLoading,
            scaleWidthToFill: scaleWidthToFill
        )
    }

    static func toolbar(isDisabled: Bool = false, isLoading: Bool = false) -> CustomButtonStyle {
        .init(
            type: .plain(customTint: nil),
            size: .regular,
            isDisabled: isDisabled,
            isLoading: isLoading,
            scaleWidthToFill: false
        )
    }
}

struct ExampleUsageView: View {
    var body: some View {
        VStack {
            Button("Primary button", role: nil, action: { })
                .buttonStyle(.primary())
            Button("Secondary button", role: nil, action: { })
                .buttonStyle(.secondary())
            Button("Toolbar button", role: nil, action: { })
                .buttonStyle(.toolbar())
        }
    }
}

// MARK: - Preview

struct ContentView: View {
    var body: some View {
        ScrollView {
            VStack {
                Button("Plain default small", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .plain(customTint: nil), size: .small, isDisabled: false, isLoading: false))
                Button("Plain default regular", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .plain(customTint: nil), size: .regular, isDisabled: false, isLoading: false))
                Button("Plain default large", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .plain(customTint: nil), size: .large, isDisabled: false, isLoading: false))
                Button("Plain custom tint", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .plain(customTint: .green), size: .regular, isDisabled: false, isLoading: false))
                Button("Plain destructive", role: .destructive, action: { })
                    .buttonStyle(CustomButtonStyle(type: .plain(customTint: nil), size: .regular, isDisabled: false, isLoading: false))
                Button("Plain loading", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .plain(customTint: nil), size: .regular, isDisabled: false, isLoading: true))
                Button("Plain disabled", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .plain(customTint: nil), size: .regular, isDisabled: true, isLoading: false))

                Divider()
            }

            VStack {
                Button("Bordered small", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .bordered(customTint: nil), size: .small, isDisabled: false, isLoading: false))
                Button("Bordered regular", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .bordered(customTint: nil), size: .regular, isDisabled: false, isLoading: false))
                Button("Bordered large", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .bordered(customTint: nil), size: .large, isDisabled: false, isLoading: false))
                Button("Bordered custom tint", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .bordered(customTint: .green), size: .regular, isDisabled: false, isLoading: false))
                Button("Bordered destructive", role: .destructive, action: { })
                    .buttonStyle(CustomButtonStyle(type: .bordered(customTint: nil), size: .regular, isDisabled: false, isLoading: false))
                Button("Bordered loading", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .bordered(customTint: nil), size: .regular, isDisabled: false, isLoading: true))
                Button("Bordered disabled", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .bordered(customTint: nil), size: .regular, isDisabled: true, isLoading: false))

                Divider()
            }

            VStack {
                Button("Prominent small", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .prominent(customBackground: nil, customForeground: nil), size: .small, isDisabled: false, isLoading: false))
                Button("Prominent regular", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .prominent(customBackground: nil, customForeground: nil), size: .regular, isDisabled: false, isLoading: false))
                Button("Prominent large", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .prominent(customBackground: nil, customForeground: nil), size: .large, isDisabled: false, isLoading: false))
                Button("Prominent custom tint", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .prominent(customBackground: .primary, customForeground: .green), size: .regular, isDisabled: false, isLoading: false))
                Button("Prominent destructive", role: .destructive, action: { })
                    .buttonStyle(CustomButtonStyle(type: .prominent(customBackground: nil, customForeground: nil), size: .regular, isDisabled: false, isLoading: false))
                Button("Prominent loading", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .prominent(customBackground: nil, customForeground: nil), size: .regular, isDisabled: false, isLoading: true))
                Button("Prominent disabled", role: nil, action: { })
                    .buttonStyle(CustomButtonStyle(type: .prominent(customBackground: nil, customForeground: nil), size: .regular, isDisabled: true, isLoading: false))
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        Group {
            ContentView()
                .previewLayout(.sizeThatFits)
            ContentView()
                .previewLayout(.sizeThatFits)
                .preferredColorScheme(.dark)

            ExampleUsageView()
                .previewLayout(.sizeThatFits)
            ExampleUsageView()
                .previewLayout(.sizeThatFits)
                .preferredColorScheme(.dark)
        }
    }
}