<!-- https://abap2ui5.github.io/docs/advanced/insights/02-the-cost-of-a-screen -->

# #2 The Cost of a Screen

An ABAP team needs a screen. A maintenance view for a customizing table nobody
wants to explain in SM30 again. A cockpit showing what last night's job
actually did. An approval step for one department. Some of these are used by
four people, twice a year. Some run during a go-live or a migration and are
never started again after that.

The logic behind such a screen might be thirty lines. The user interface in
front of it is not, and — this is the part that hurts — it does not scale down
with the logic: a data model, a service, a binding, an annotation model, a
frontend artifact, a deployment. Every one of those objects then exists
forever, unless somebody remembers to delete it.

None of that is waste. It is what makes a real application dependable. It is
simply a *fixed* cost, and a fixed cost is brutal to a small thing.

So the screen does not get built. Or it becomes a selection screen and an ALV
grid, and everyone agrees to stop thinking about it. Every system has a `Z`
package full of those, and every one of them was a reasonable decision at the
time.

Here is the job monitor as a UI5 app instead — not an excerpt, the whole
application:

```abap
CLASS zcl_job_monitor DEFINITION PUBLIC.

  PUBLIC SECTION.
    INTERFACES z2ui5_if_app.

    TYPES:
      BEGIN OF ty_s_run,
        job    TYPE string,
        finish TYPE string,
        state  TYPE string,
      END OF ty_s_run.

    DATA runs TYPE STANDARD TABLE OF ty_s_run WITH EMPTY KEY.

  PROTECTED SECTION.
    DATA client TYPE REF TO z2ui5_if_client.
    METHODS set_view.
    METHODS model_init.

  PRIVATE SECTION.
ENDCLASS.


CLASS zcl_job_monitor IMPLEMENTATION.

  METHOD z2ui5_if_app~main.

    me->client = client.
    IF client->check_on_init( ).
      model_init( ).
    ENDIF.
    set_view( ).

  ENDMETHOD.

  METHOD set_view.

    DATA(view) = z2ui5_cl_ui5_view_builder=>factory(
        )->ele( n = `View` ns = `mvc`
            )->a( n = `xmlns`     v = `sap.m`
            )->a( n = `xmlns:mvc` v = `sap.ui.core.mvc`

            )->ele( `Page`
                )->a( n = `title` v = `Last night`

                )->ele( `Table`
                    )->a( n = `items` v = client->_bind( runs )

                    )->ele( `columns`
                        )->ele( `Column`
                            )->tag( `Text`
                                )->a( n = `text` v = `Job`
                        )->end(
                        )->ele( `Column`
                            )->tag( `Text`
                                )->a( n = `text` v = `Finished`
                        )->end(
                        )->ele( `Column`
                            )->tag( `Text`
                                )->a( n = `text` v = `State`
                        )->end(
                    )->end(

                    )->ele( `items`
                        )->ele( `ColumnListItem`
                            )->ele( `cells`
                                )->tag( `Text`
                                    )->a( n = `text` v = `{JOB}`
                                )->tag( `Text`
                                    )->a( n = `text` v = `{FINISH}`
                                )->tag( `ObjectStatus`
                                    )->a( n = `text`  v = `{STATE}`
                                    )->a( n = `state` v = `{STATE}` ).

    client->view_display( view->stringify( ) ).

  ENDMETHOD.

  METHOD model_init.
    runs = VALUE #( ( job = `ZFI_POSTING`  finish = `03:14`  state = `Success` )
                    ( job = `ZMM_REORG`    finish = `03:41`  state = `Warning` )
                    ( job = `ZSD_INVOICES` finish = `04:02`  state = `Error` ) ).
  ENDMETHOD.

ENDCLASS.
```

Activate it, call the ICF endpoint with `?app_start=zcl_job_monitor`, and it is
on screen. About as much work as an ALV — except this one follows the Fiori
design guidelines, and starts on your phone too.

Replace `model_init( )` with the `SELECT` that reads your job log, and it is
finished. Nothing published, nothing to deprecate, nothing anybody has to
un-build in three years.

abap2UI5 is not a replacement for your RAP or UI5 apps. It is an addition to
the UI5 solutions you already run — especially for small programs, and for the
screen somebody needs exactly once.

Install it with abapGit and give it a try!

A screen that costs one class is a screen that gets built.

*The article before this one:
[#1 Somewhere on the Way to UI5, We Lost RTTS](/advanced/insights/01-somewhere-on-the-way-to-ui5)
— a table whose structure is only known at runtime, drawn in UI5.*