# authenticate property

void authenticate= (Future<bool> f(Uri url, String scheme, String realm))

Sets the function to be called when a site is requesting authentication. The URL requested and the security realm from the server are passed in the arguments `url` and `realm`.

The function returns a Future which should complete when the authentication has been resolved. If credentials cannot be provided the Future should complete with `false`. If credentials are available the function should add these using addCredentials before completing the Future with the value `true`.

If the Future completes with true the request will be retried using the updated credentials. Otherwise response processing will continue normally.

## Implementation

    set authenticate(Future<bool> f(Uri url, String scheme, String realm));