Contacts Framework

# Contacts Framework

Fetch, create, update, and pick contacts from the user's Contacts database using
`CNContactStore`, `CNSaveRequest`, and `CNContactPickerViewController`. Targets
Swift 6.3 / iOS 26+.

## Contents

- [Setup](#setup)
- [Authorization](#authorization)
- [Fetching Contacts](#fetching-contacts)
- [Key Descriptors](#key-descriptors)
- [Creating and Updating Contacts](#creating-and-updating-contacts)
- [Contact Picker](#contact-picker)
- [Observing Changes](#observing-changes)
- [Common Mistakes](#common-mistakes)
- [Review Checklist](#review-checklist)
- [References](#references)

## Setup

### Project Configuration

1. Add `NSContactsUsageDescription` to Info.plist explaining why the app accesses contacts
2. No additional capability or entitlement is required for basic Contacts access
3. For contact notes access, add the `com.apple.developer.contacts.notes` entitlement

### Imports

```swift
import Contacts       // CNContactStore, CNSaveRequest, CNContact
import ContactsUI     // CNContactPickerViewController
```

## Authorization

Request access before fetching or saving contacts. The picker (`CNContactPickerViewController`)
does not require authorization -- the system grants access only to the contacts
the user selects.

```swift
let store = CNContactStore()

func requestAccess() async throws -> Bool {
    return try await store.requestAccess(for: .contacts)
}

// Check current status without prompting
func checkStatus() -> CNAuthorizationStatus {
    CNContactStore.authorizationStatus(for: .contacts)
}
```

### Authorization States

| Status | Meaning |
|---|---|
| `.notDetermined` | User has not been prompted yet |
| `.authorized` | Full read/write access granted |
| `.denied` | User denied access; direct to Settings |
| `.restricted` | Parental controls or MDM restrict access |
| `.limited` | iOS 18+: user granted access to selected contacts only |

## Fetching Contacts

Use `unifiedContacts(matching:keysToFetch:)` for predicate-based queries.
Use `enumerateContacts(with:usingBlock:)` for batch enumeration of all contacts.

### Fetch by Name

```swift
func fetchContacts(named name: String) throws -> [CNContact] {
    let predicate = CNContact.predicateForContacts(matchingName: name)
    let keys: [CNKeyDescriptor] = [
        CNContactGivenNameKey as CNKeyDescriptor,
        CNContactFamilyNameKey as CNKeyDescriptor,
        CNContactPhoneNumbersKey as CNKeyDescriptor
    ]
    return try store.unifiedContacts(matching: predicate, keysToFetch: keys)
}
```

### Fetch by Identifier

```swift
func fetchContact(identifier: String) throws -> CNContact {
    let keys: [CNKeyDescriptor] = [
        CNContactGivenNameKey as CNKeyDescriptor,
        CNContactFamilyNameKey as CNKeyDescriptor,
        CNContactEmailAddressesKey as CNKeyDescriptor
    ]
    return try store.unifiedContact(withIdentifier: identifier, keysToFetch: keys)
}
```

### Enumerate All Contacts

Perform I/O-heavy enumeration off the main thread.

```swift
func fetchAllContacts() throws -> [CNContact] {
    let keys: [CNKeyDescriptor] = [
        CNContactGivenNameKey as CNKeyDescriptor,
        CNContactFamilyNameKey as CNKeyDescriptor
    ]
    let request = CNContactFetchRequest(keysToFetch: keys)
    request.sortOrder = .givenName

    var contacts: [CNContact] = []
    try store.enumerateContacts(with: request) { contact, _ in
        contacts.append(contact)
    }
    return contacts
}
```

## Key Descriptors

Only fetch the properties you need. Accessing an unfetched property throws
`CNContactPropertyNotFetchedException`.

### Common Keys

| Key | Property |
|---|---|
| `CNContactGivenNameKey` | First name |
| `CNConta