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. The app crashes if it uses contact data APIs without this key.
2. No additional capability or entitlement is required for ordinary Contacts access.
3. Add `com.apple.developer.contacts.notes` only when reading or writing `CNContactNoteKey` / `CNContact.note`; this entitlement requires Apple approval before public distribution.

### Imports

```swift
@preconcurrency 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 |

Treat both `.authorized` and `.limited` as usable Contacts API states. With
`.limited`, fetch, edit, and delete operations only apply to contacts the user
granted or the app created. Use `ContactAccessButton` or
`contactAccessPicker(isPresented:completionHandler:)` to let users add contacts
to the app's limited-access set.

## Fetching Contacts

Use `unifiedContacts(matching:keysToFetch:)` for predicate-based queries.
Use `enumerateContacts(with:usingBlock:)` for batch enumeration of all contacts.
For large cached address books, first fetch identifiers, then fetch detailed
contacts in batches by identifier.

### 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 |
| `CNContactFamilyNameKey` | Last name |
| `CNContactPhoneNumbersKey` | Phone numbers array |
| `CNContactEmailAddressesKey` | Email addresses array |
| `CNContactPostalAddressesKey` | Mailing addresses array |
| `CNContactImageDataKey` | Full-resolution contact photo |
| `CNContactThumbnailImageDataKey` | Thumbnail contact photo |
| `CNContactBirthdayKey` | Birthday date components |
| `CNContactOrganizationNameKey` | Company name |

### Composite Key Descriptors

Use `CNContactFormatter.descriptorForRequiredKeys(for:)` to fetch all keys needed
for formatting a contact's name.

```swift
let nameKeys = CNContactFormatter.descriptorForRequiredKeys(for: .fullName)
let keys: [CNKeyDescriptor] = [nameKeys, CNContactPhoneNumbersKey as CNKeyDescriptor]
```

## Creating and Updating Contacts

Use `CNMutableContact` to build new contacts and `CNSaveRequest` to persist changes.

### Creating a New Contact

```swift
func createContact(givenName: String, familyName: String, phone: String) throws {
    let contact = CNMutableContact()
    contact.givenName = givenName
    contact.familyName = familyName
    contact.phoneNumbers = [
        CNLabeledValue(
            label: CNLabelPhoneNumberMobile,
            value: CNPhoneNumber(stringValue: phone)
        )
    ]

    let saveRequest = CNSaveRequest()
    saveRequest.add(contact, toContainerWithIdentifier: nil) // nil = default container
    try store.execute(saveRequest)
}
```

### Updating an Existing Contact

You must fetch the contact with the properties you intend to modify, create a
mutable copy, change the properties, then save.

```swift
func updateContactEmail(identifier: String, email: String) throws {
    let keys: [CNKeyDescript