返回（AWSTask <nsstring * =“”>）没有错误

Question

我从AWS文档中获得以下代码：

@implementation DeveloperAuthenticatedIdentityProvider / *  *使用令牌方法与后端通信以获得  * identityId和token。  * /

- (AWSTask <NSString*>) token {
    //Write code to call your backend:
    //Pass username/password to backend or some sort of token to authenticate user
    //If successful, from backend call getOpenIdTokenForDeveloperIdentity with logins map 
    //containing "your.provider.name":"enduser.username"
    //Return the identity id and token to client
    //You can use AWSTaskCompletionSource to do this asynchronously

    // Set the identity id and return the token
    self.identityId = response.identityId;
    return [AWSTask taskWithResult:response.token];
}

@end

我如何返回（AWSTask）？我有另一种方法的令牌，它是NSString *令牌形式。

文档： http://docs.aws.amazon.com/cognito/latest/developerguide/developer-authenticated-identities.html