How to Build a Blood Pressure Tracker App in SwiftUI

import SwiftData
import Foundation

@Model
final class BPReading {
    var id: UUID = UUID()
    var systolic: Int
    var diastolic: Int
    var pulse: Int?
    var timestamp: Date = Date()

    init(systolic: Int, diastolic: Int, pulse: Int? = nil) {
        self.systolic = systolic
        self.diastolic = diastolic
        self.pulse = pulse
    }

    var category: String {
        switch systolic {
        case ..<120:    "Normal"
        case 120..<130: "Elevated"
        case 130..<140: "Stage 1 Hypertension"
        default:        "Stage 2 Hypertension"
        }
    }
}

struct BPDashboardView: View {
    @Environment(\.modelContext) private var modelContext
    @Query(sort: \BPReading.timestamp, order: .reverse) var readings: [BPReading]
    @State private var showLogger = false

    var body: some View {
        NavigationStack {
            List {
                BPTrendChart(readings: Array(readings.prefix(30)))
                    .frame(height: 180)
                    .listRowSeparator(.hidden)
                ForEach(readings) { BPReadingRow(reading: $0) }
                    .onDelete { offsets in
                        offsets.forEach { modelContext.delete(readings[$0]) }
                    }
            }
            .listStyle(.plain)
            .navigationTitle("Blood Pressure")
            .toolbar {
                Button { showLogger = true } label: {
                    Image(systemName: "plus.circle.fill")
                }
            }
            .sheet(isPresented: $showLogger) { LogBPView() }
        }
    }
}

import Charts

struct BPTrendChart: View {
    let readings: [BPReading]
    private var sorted: [BPReading] {
        readings.sorted { $0.timestamp < $1.timestamp }
    }

    var body: some View {
        Chart {
            ForEach(sorted) { r in
                LineMark(x: .value("Date", r.timestamp, unit: .day),
                         y: .value("Systolic", r.systolic))
                    .foregroundStyle(.red.gradient)
                LineMark(x: .value("Date", r.timestamp, unit: .day),
                         y: .value("Diastolic", r.diastolic))
                    .foregroundStyle(.blue.gradient)
            }
            RuleMark(y: .value("Stage 1", 130))
                .lineStyle(StrokeStyle(lineWidth: 1, dash: [5]))
                .foregroundStyle(.orange.opacity(0.7))
        }
        .chartYScale(domain: 50...200)
        .chartLegend(position: .bottom)
    }
}

// 1. Add PrivacyInfo.xcprivacy (File → New → Resource → App Privacy)
//    NSPrivacyAccessedAPICategoryUserDefaults → CA92.1

// 2. Info.plist — required HealthKit usage strings:
//    NSHealthShareUsageDescription  → "Read past BP readings from Health."
//    NSHealthUpdateUsageDescription → "Save BP readings to Apple Health."

// 3. Entitlements: com.apple.developer.healthkit = YES

// 4. Request authorization at launch (real device only):
import HealthKit

func requestHealthKitAccess() async {
    guard HKHealthStore.isHealthDataAvailable() else { return }
    let store = HKHealthStore()
    let bpTypes: Set<HKSampleType> = [
        HKQuantityType(.bloodPressureSystolic),
        HKQuantityType(.bloodPressureDiastolic)
    ]
    try? await store.requestAuthorization(toShare: bpTypes, read: bpTypes)
}