Generic Animated Progress Bar in SwiftUI

NutrientModel.swift

import Foundation
import UIKit
import SwiftUI
import Combine

class NutrientModel: Progressable {
  
  var willChange = PassthroughSubject<BaseNutrient, Never>()
  var id = UUID.init()
  var name: String
  var description: String {
    get {
      return "\(current) / \(total)"
    }
  }
  
  var current: CGFloat
  var total: CGFloat
  var progress: CGFloat {
    get {
      return current / total
    }
  }
 
  
  var gradient: LinearGradient
  
  init(name: String, unit: NutrientUnit, total: CGFloat, colors: [Color] = [Color(red: 239.0 / 255, green: 120.0 / 255, blue: 221.0 / 255), Color(red: 239.0 / 255, green: 172.0 / 255, blue: 120.0 / 255)], start: CGFloat = 0) {
    self.name    = name
    self.total   = total
    self.current = start
    self.gradient = LinearGradient(gradient: .init(colors: colors), startPoint: .init(x: 0.0, y: 0),
        endPoint: .init(x: 1.0, y: 0))
  }
  
  func addProgress(_ progress: CGFloat) {
    willChange.send(self)
    self.current += progress
  }
  
  func removeProgress(_ progress: CGFloat) {
    willChange.send(self)
    self.current -= progress
    if self.current < 0 {
      self.current = 0
    }
  }
}

Progressable.swift

import SwiftUI

protocol Progressable: ObservableObject {
  
  /// Name of the progressable field
  var name: String { get }
  
  /// The text form of the progress being made (ex. formatted percentage or fraction)
  var description: String { get }
  
  /// The percentage of progress made as float
  var progress: CGFloat { get }
  
  /// The linear gradient use to fill the completed portion of the bar
  var gradient: LinearGradient { get set }
  
}

ProgressBarComponent.swift

import SwiftUI

struct ProgressBarComponent<P: Progressable> : View {
  @ObservedObject var progression: P
  var progressAnimation: Animation {
    Animation
      .interpolatingSpring(mass: 43, stiffness: 3.2, damping: 0.5)
    .speed(3)
    .delay(0.07)
  }
  var barHeight: CGFloat = 12.0
  
  var body: some View {
    VStack {
      HStack {
        Text(self.progression.name)
          .font(.subheadline)
          .foregroundColor(.gray)
        Spacer()
        Text(self.progression.description)
          .font(.subheadline)
          .foregroundColor(.gray)
      }
        .padding(.bottom, -8)
        .padding(.horizontal, 4)
      ZStack {
        GeometryReader { geometry in
          RoundedRectangle(cornerRadius: 100.0)
          .fill(
            Color(.displayP3,
              red: 150 / 255,
              green: 150 / 255,
              blue: 150 / 255,
              opacity: 0.1)
          )
          .overlay(
            RoundedRectangle(cornerRadius: 100.0)
                .size(
                  width: max(geometry.size.width * self.progression.progress, self.barHeight),
                  height: geometry.size.height)
                .fill(self.progression.gradient)
                .animation(self.progressAnimation)
          )
        }
      }
      .frame(height: self.barHeight, alignment: .leading)
    }
  }
}

ProgressContainerView.swift

import SwiftUI

struct DayProgressContainer : View {
  var trackedNutreints: [NutrientModel]
  var body: some View {
    return VStack {
      ForEach(self.trackedNutreints, id: \.self) { nutrient in
        ProgressBarComponent(progression: nutrient)
          .padding(.vertical, 4)
      }
    }
  }
}

Examples

Need to make the following changes for the lates version of SwiftUI.

Change in Progressable.swift
protocol Progressable: BindableObject {

To
protocol Progressable: ObservableObject {

Change in ProgressBarComponent.swift
@ObjectBinding var progression: P

To
@ObservedObject var progression: P

Thanks @mwcs01! I went ahead and updated a few other API changes (foregroundColor) as well.

I have been struggling on how to use it. Any chance you could include how you used it to create one of your example views above?

@mwcs01 I added an example--I didn't have a chance to test it, but hopefully you get the idea? This code is a bit different in my app now, I'll try to update it sometime soon.

Thanks!