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Flash Messages

Flash messages allow you to pass temporary messages - info/error or otherwise - across multiple web requests via a user's current session.

For example, in sign-up logic you could set a flash error message for an invalid email address; retrieving the message from the session on a redirect for the view, allowing the view to render error messages.

Important

To use flash messages you need to have Session Middleware enabled.

Usage

The flash functions allow you to add, get, and remove messages on a user's session.

If you call Add-PodeFlashMessage using the same Name multiple times, then the messages will be appended as an array. Calling Add-PodeFlashMessage for a Name will remove all messages from the current session for the Name supplied.

The following is an example of adding a flash message to a session, this will add a message under the email-error key:

Add-PodeFlashMessage -Name 'email-error' -Message 'Invalid email address'

Then to retrieve the message, you can do this in a Route for a View:

Add-PodeRoute -Method Get -Path '/signup' -ScriptBlock {
    Write-PodeViewResponse -Path 'signup' -Data @{
        Errors = @{
            Email = (Get-PodeFlashMessage -Name 'email-error')
        }
    }
}

Views

The Write-PodeViewResponse function has a helper switch (-FlashMessages) to load all current flash messages in the session, into the views data - to save time writing lots of Write-PodeViewResponse calls. When used, all messages will be loaded into the $data argument supplied to dynamic views, and accessible under $data.flash.

For example, somewhere we could have a sign-up flow which fails validation and adds two messages to the session:

Add-PodeFlashMessage -Name 'email-error' -Message 'Invalid email address'
Add-PodeFlashMessage -Name 'name-error' -Message 'No first/last name supplied'

Then, within your route to load the sign-up view, you can use the switch to automatically load all current flash messages:

Add-PodeRoute -Method Get -Path '/signup' -ScriptBlock {
    Write-PodeViewResponse 'signup' -FlashMessages
}

With this, the two flash messages for email-error and name-error are automatically added to a dynamic view's $data.flash property. You could get these back in the view, such as the snippet of a possible signup.pode:

<html>
    <head>...</head>
    <body>
        <form action="/signup" method="post">

            <!-- The email input control -->
            <label>Email Address:</label>
            <input type="text" id="email" name="email" />

            <!-- Check if there's a flash error, and display it -->
            $(if ($data.flash['email-error']) {
                "<p class='error'>$($data.flash['email-error'])</p>"
            })
        </form>
    </body>
</html>

Authentication

When doing authentication checks, normally if the check fails Pode will throw an error and return with a 401 status code. These errors are also stored in the current Session's Flash messages under an auth-error key - if sessions are enabled.

For example, here we have a login page, with the POST login check. Any authentication errors will be loaded into the session's flash messages:

Add-PodeRoute -Method Get -Path '/login' -Authentication Login -Login -ScriptBlock {
    Write-PodeViewResponse -Path 'auth-login' -FlashMessages
}

Add-PodeRoute -Method Post -Path '/login' -Authentication Login -Login

Then, to load the authentication back for the user:

<html>
    <head>...</head>
    <body>
        <form action="/login" method="post">
            <!-- The username control -->
            <label>Username:</label>
            <input type="text" name="username"/>

            <!-- The password control -->
            <label>Password:</label>
            <input type="password" name="password"/>
        </form>

        <!-- Check if there's a flash error, and display it -->
        $(if ($Data.flash['auth-error']) {
            "<p class='error'>$($data.flash['auth-error'])</p>"
        })

    </body>
</html>
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