Adding an Extension

For the extension to function, it first needs to be installed by the Kiosk owner. To achieve that, an extension needs to implement the add function which will be called by the Kiosk owner and will request all necessary permissions.

Implementing add function

The signature of the kiosk_extension::add function requires the extension witness making it impossible to install an extension without an explicit implementation provided by the extension. The following example shows how to implement the add function for an extension that requires the place permission:

module examples::letterbox_ext {
    // ... dependencies

    /// The expected set of permissions for extension. It requires `place`.
    const PERMISSIONS: u128 = 1;

    /// The Witness struct used to identify and authorize the extension.
    struct Extension has drop {}

    /// Install the Mallbox extension into the Kiosk.
    public fun add(kiosk: &mut Kiosk, cap: &KioskOwnerCap, ctx: &mut TxContext) {
        kiosk_extension::add(Extension {}, kiosk, cap, PERMISSIONS, ctx)