open interface B in interface A in portal

Question

Hi All, 
 I have a Signup form on the appian portals. 
 case 1: I want when I click on the Login then Open the Login UI. 
 Interface A: 
 And when the user enter all the details in the Signup form once and submit the form all the details are save in DB. 
 case 2: I want if the same user again come in Portal and signup form fill then show a message "you already have an account please login". In that case how to check the details of user in DB is present or not and show the message? 
 Interface B: a!localVariables(
 local!accountDetails: a!map(firstName: null, lastName: null, email: null,Password: null),

 a!sectionLayout(
 contents: {
 a!columnsLayout(
 columns: {
 a!columnLayout(contents: {}),
 a!columnLayout(contents: {}),
 a!columnLayout(
 contents: {
 a!cardLayout(
 contents: {
 a!cardLayout(
 /* Create Account */
 contents: {
 a!richTextDisplayField(
 labelPosition: "COLLAPSED",
 value: {
 a!richTextItem(
 text: "Create account",
 color: "#434343",
 size: "LARGE",
 style: "STRONG"
 )
 },
 marginBelow: "STANDARD"
 ),
 a!richTextDisplayField(
 labelPosition: "COLLAPSED",
 value: {
 a!richTextItem(
 text: "Already have an account?",
 color: "#666666"
 ),
 " ",
 a!richTextItem(
 text: {
 a!richTextItem(
 text: "Log in",
 color: "ACCENT"
 )
 },
 link:
 a!dynamicLink(
 value:rule!TestLoginUI(),
 )
 
 )
 },
 marginBelow: "MORE"
 ),
 a!textField(
 label: "First Name",
 value: local!accountDetails.firstname,
 saveInto: local!accountDetails.firstname
 ),
 a!textField(
 label: "Last Name",
 value: local!accountDetails.lastname,
 saveInto: local!accountDetails.lastname
 ),
 a!textField(
 label: "Email",
 value: local!accountDetails.email,
 saveInto: local!accountDetails.email
 ),
 a!textField(
 label: "Password",
 value: local!accountDetails.Password,
 saveInto: local!accountDetails.Password,
 ),
 a!buttonArrayLayout(
 buttons: {
 a!buttonWidget(
 label: "Signup account",
 width: "FILL",
 style: "SOLID"
 )
 },
 align: "START",
 marginAbove: "MORE"
 )
 },
 shape: "ROUNDED",
 padding: "MORE",
 marginBelow: "STANDARD",
 showBorder: false,
 showShadow: true
 )
 },
 /*style: local!backgroundColor,*/
 padding: "EVEN_MORE",
 showBorder: false
 )
 },
 width: "WIDE"
 ),
 a!columnLayout(contents: {}),
 a!columnLayout(contents: {})
 },
 alignVertical: "MIDDLE",
 stackWhen: { "PHONE", "TABLET_PORTRAIT" }
 )
 },
 
 ),
 
 
) Please help me for both the cases Thanks

Mike Schmitt · Answer

I think the most basic solution is that you'll need to rely on the user to know whether they've signed up, and just have a SafeLink on your portal form saying i.e. "Click Here if you've already signed up for an account" - linking to the normal sign-in page. There is probably a way you could have the user enter their username and use a Web API to retrieve from your environment whether the account already exists, but it doesn't add all that much IMHO and is a lot of extra work for not much gain.