# Migrating from 0.16.x-beta to 0.17.0-alpha.x

## Changes to Demo APP
The demo application now uses the SDKSynchronizer to create addresses and
shield funds.
`DerivationToolViewController` was removed. See `DerivationTool` unit tests
for sample code.
`GetAddressViewController` now derives transparent and sapling addresses
from Unified Address
`SendViewController` uses Unified Spending Key and type-safe `Memo`

## Changes To SDK
### `CompactBlockProcessor`
`public func getUnifiedAddress(accountIndex: Int) -> UnifiedAddress?`
`public func getSaplingAddress(accountIndex: Int) -> SaplingAddress?` derived from UA
`public func getTransparentAddress(accountIndex: Int) -> TransparentAddress?`
is derived from UA
`public func getTransparentBalance(accountIndex: Int) throws -> WalletBalance` now
fetches from account exclusively
`func refreshUTXOs(tAddress: TransparentAddress, startHeight: BlockHeight) async throws -> RefreshedUTXOs`
uses `TransparentAddress`

### Initializer
Migration of DataDB and CacheDB are delegated to `librustzcash`

removed `public func getAddress(index account: Int = 0) -> String`


### Wallet Types
`UnifiedSpendingKey` to represent Unified Spending Keys. This is a binary
encoded not meant to be stored or backed up. This only serves the purpuse
of letting clients use the least priviledge keys at all times for every
operation.

### Synchronizer
`sendToAddress` and `shieldFunds` now take a `UnifiedSpendingKey` instead
of the respective spending and transparent private keys.
`refreshUTXOs` uses `TransparentAddress`

### KeyDeriving protocol
Addresses should be obtained from the `Synchronizer` by using the `get_address` functions
Transparent and Sapling receivers should be obtained by extracting the receivers of a UA
````Swift
public extension UnifiedAddress {
    /// Extracts the sapling receiver from this UA if available
    /// - Returns: an `Optional<SaplingAddress>`
    func saplingReceiver() -> SaplingAddress? {
        try? DerivationTool.saplingReceiver(from: self)
    }

    /// Extracts the transparent receiver from this UA if available
    /// - Returns: an `Optional<TransparentAddress>`
    func transparentReceiver() -> TransparentAddress? {
        try? DerivationTool.transparentReceiver(from: self)
    }
````

**Removed**
`func deriveUnifiedFullViewingKeys(seed: [UInt8], numberOfAccounts: Int) throws -> [UnifiedFullViewingKey]`
`func deriveViewingKey(spendingKey: SaplingExtendedSpendingKey) throws -> SaplingExtendedFullViewingKey`
`func deriveSpendingKeys(seed: [UInt8], numberOfAccounts: Int) throws -> [SaplingExtendedSpendingKey]`
`func deriveUnifiedAddress(from ufvk: UnifiedFullViewingKey) throws -> UnifiedAddress`
`func deriveTransparentAddress(seed: [UInt8], account: Int, index: Int) throws -> TransparentAddress`
`func deriveTransparentAccountPrivateKey(seed: [UInt8], account: Int) throws -> TransparentAccountPrivKey`
`func deriveTransparentAddressFromAccountPrivateKey(_ xprv: TransparentAccountPrivKey, index: Int) throws -> TransparentAddress`

**Added**
`static func saplingReceiver(from unifiedAddress: UnifiedAddress) throws -> SaplingAddress?`
`static func transparentReceiver(from unifiedAddress: UnifiedAddress) throws -> TransparentAddress?`
`static func receiverTypecodesFromUnifiedAddress(_ address: UnifiedAddress) throws -> [UnifiedAddress.ReceiverTypecodes]`
`func deriveUnifiedSpendingKey(seed: [UInt8], accountIndex: Int) throws -> UnifiedSpendingKey`
`public func deriveUnifiedFullViewingKey(from spendingKey: UnifiedSpendingKey) throws -> UnifiedFullViewingKey`

## Notes on Structured Concurrency

`CompactBlockProcessor` is now an Swift Actor. This makes it more robust and have its own
async environment. 

SDK Clients will likely be affected by some `async` methods on `SDKSynchronizer`. 

We recommend clients that don't support structured concurrency features, to work around this by  surrounding the these function calls either in @MainActor contexts either by marking callers as @MainActor or launching tasks on that actor with `Task { @MainActor in ... }`