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Documentation Index

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Abstract Base Class Base class for email / phone non-custodial signers. 
abstract base class CrossmintNonCustodialSigner implements CrossmintWalletApprovalSigner, CrossmintExportableWalletSigner
Signing happens inside a hidden WebView (the Crossmint signer runtime) coordinated through CrossmintSignerBridgeClient. The SDK owns the WebView’s lifecycle via CrossmintWalletHost — if it is not mounted, attempting to use a non-custodial signer throws CrossmintSignerException(code: nonCustodialBridgeHostNotMounted). When authentication is needed, the signer calls onAuthRequired which surfaces the OTP challenge to UI (typically via CrossmintWalletController.otp). Concurrent callers are coalesced onto the same in-flight auth future to avoid double-prompting. Non-custodial signers are also CrossmintExportableWalletSigners — email/phone signers can export their private key via exportPrivateKey.

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Constructors

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CrossmintNonCustodialSigner

CrossmintNonCustodialSigner({
  required this.client,
  required this.bridge,
  required this.type,
  required this.locator,
  this.address,
  this.onAuthRequired,
  CrossmintSignerBridgeClient? bridgeClient,
})
Creates a non-custodial signer. Prefer the chain-specific factory on CrossmintClient (e.g. createEvmNonCustodialSigner) over constructing this directly.

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Properties

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client

final CrossmintClient client
The client this signer belongs to.

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bridge

final HiddenSignerBridge bridge
The hidden signer WebView bridge that hosts the signing runtime.

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type

final String type

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locator

final String locator

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address

final String? address
The wallet address this signer approves for, if known at construction.

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onAuthRequired

final CrossmintSignerAuthRequiredCallback? onAuthRequired
Callback invoked when an OTP challenge starts or ends. Usually wired to CrossmintWalletController.onAuthRequired — which in turn surfaces a reactive challenge on CrossmintWalletController.otp.

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needsAuth

bool get needsAuth
true while an OTP challenge is outstanding.

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canExportPrivateKey

bool get canExportPrivateKey

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Methods

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ensureAuthenticated

Future<void> ensureAuthenticated()
Ensures the signer runtime has completed its authentication handshake, prompting the user via onAuthRequired if necessary. Concurrent callers share the same in-flight future — the user sees at most one prompt per auth cycle.

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signMessage

Future<String> signMessage(String message)

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signTransaction

Future<String> signTransaction(String transaction)

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sign

Future<String> sign({
  required CrossmintSignerKeyType keyType,
  required String bytes,
  required CrossmintSignerEncoding encoding,
})
Low-level sign primitive — ensures auth, then invokes the signer bridge directly. Chain-specific subclasses wrap this with the encoding / key-type appropriate for their chain.

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sendOtp

Future<void> sendOtp()
(Re-)sends the OTP to the signer locator (email / phone). Meant to be invoked via CrossmintWalletOtpController.sendOtp during an active challenge.

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exportPrivateKey

Future<void> exportPrivateKey(CrossmintExportSignerBridge bridge)

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verifyOtp

Future<void> verifyOtp(String otp)
Submits the OTP the user entered. Resolves the pending ensureAuthenticated future on success.

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reject

void reject([Object? error])
Cancels the pending OTP challenge. Fails the pending ensureAuthenticated future with CrossmintAuthRejectedException when no cause is supplied.