Binding

In abap2UI5 you share data between your ABAP code and the UI5 frontend with client->_bind( ). There is only one binding, and it works in both directions: when the value is changed in an editable control, the framework writes it back to your ABAP attribute before the next event handler runs. Only the paths the user actually edited are transported back (a delta), so read-only data costs nothing on the way back.

Displaying Data

Bind an attribute to a display-only control (e.g. text) — nothing is editable there, so nothing syncs back:

CLASS zcl_app_hello_world DEFINITION PUBLIC.

  PUBLIC SECTION.
    INTERFACES z2ui5_if_app.
    DATA name TYPE string.

  PROTECTED SECTION.
  PRIVATE SECTION.
ENDCLASS.

CLASS zcl_app_hello_world IMPLEMENTATION.
  METHOD z2ui5_if_app~main.

    IF client->check_on_navigated( ).

      name = `World`.

      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 = `abap2UI5 - Hello World`

                  )->tag( `Text`
                      )->a( n = `text` v = `My Text`
                  )->tag( `Text`
                      )->a( n = `text` v = client->_bind( name ) ).

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

    ENDIF.

  ENDMETHOD.
ENDCLASS.

This method works with tables, trees, and other nested data structures — see Tables and Trees.

Editing Data

Bind an attribute to an editable control (e.g. input). After an event, the framework has already synced the user's changes back to your ABAP attribute:

CLASS zcl_app_hello_world DEFINITION PUBLIC.

  PUBLIC SECTION.
    INTERFACES z2ui5_if_app.
    DATA name TYPE string.

  PROTECTED SECTION.
  PRIVATE SECTION.
ENDCLASS.

CLASS zcl_app_hello_world IMPLEMENTATION.
  METHOD z2ui5_if_app~main.

    IF client->check_on_navigated( ).

      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 = `abap2UI5 - Hello World`

                  )->tag( `Text`
                      )->a( n = `text` v = `Enter your name`
                  )->tag( `Input`
                      )->a( n = `value` v = client->_bind( name )
                  )->tag( `Button`
                      )->a( n = `text`  v = `post`
                      )->a( n = `press` v = client->_event( `POST` ) ).

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

    ELSEIF client->check_on_event( `POST` ).
      client->message_box_display( |Your name is { name }.| ).

    ENDIF.

  ENDMETHOD.
ENDCLASS.

The view is built once, in the check_on_navigated( ) branch; the POST branch only reads name, which the framework has already written back. It does not call view_display( ) again — the view on screen is still right, only the data changed. See Life Cycle for why every app is shaped this way.

Bound Attributes Must Be Public

_bind( ) resolves your class attributes from outside the controller via dynamic ASSIGN, and it only sees the PUBLIC SECTION. Passing a PROTECTED or PRIVATE attribute — or a local variable — is not silent: the framework finds no attribute for the reference and raises

BINDING_ERROR - No class attribute for binding found -
Please check if the bound values are public attributes of your class

which reaches the browser as a 500 and is shown in the error view. The compiler cannot catch it (the call takes TYPE data), but the runtime says exactly what is wrong.

Always declare bound data in PUBLIC SECTION. This resembles the PAI/PBO logic, where data lived in global variables. See also Life Cycle → Lifecycle Pitfalls.

Binding to Structures

When the bound attribute is a structure, refer to a field directly with the - component selector. The framework generates one model path per field — the structure name and the component name, in upper case, joined by /:

TYPES: BEGIN OF ts_order,
         customer TYPE string,
         material TYPE string,
         quantity TYPE i,
       END OF ts_order.

DATA edit_row TYPE ts_order.

...

)->tag( `Input`
    )->a( n = `value` v = client->_bind( edit_row-customer )   " resolves to {/EDIT_ROW/CUSTOMER}
)->tag( `Input`
    )->a( n = `value` v = client->_bind( edit_row-material )
)->tag( `Input`
    )->a( n = `value` v = client->_bind( edit_row-quantity )

Nested structures follow the same rule recursively (edit_row-address-city → /EDIT_ROW/ADDRESS/CITY). Internal tables of structures use one row context per item — see Tables.

_bind( ) Options

client->_bind( name ) is the whole call in most places. The optional parameters cover the cases where the default shape of the model is not what the control needs:

Parameter	What it does
path = abap_true	returns the model path of the attribute (/NAME) instead of the binding ({/NAME}) — what a parts: array, a binding_call filter or sorter and bind_element need. _bind_path( ) is the same thing under a readable name, see below
tab / tab_index	bind one cell of an internal table: pass the table as tab, the row number (1-based, the ABAP way) as tab_index, and the row's component itself as val — _bind( val = mt_emp[ 1 ]-name tab = mt_emp tab_index = 1 ) renders {/MT_EMP/0/NAME}. The cell is found by reference, so a copy of the value is refused with BINDING_ERROR_TAB_CELL_LEVEL. For a repeating aggregation bind the table itself and keep the template's fields relative
omit_initial	leaves initial fields out of the serialized model instead of sending them as "", 0 or false. An ABAP field is never absent, so by default every field reaches the client as an explicit value, which overrides the UI5 property default — and an enum-typed property rejects the empty string outright. Set it when the rows of a bound template fill different subsets of the same properties
omit_initial_paths	the same omission scoped to the listed fields (upper-case column names). For the case where the blanket flag is too coarse: an abap_false that must reach the client is itself initial, so list the numeric and enum columns and leave the booleans
json	the bound string already contains JSON — it is spliced into the model as a node instead of being sent as a quoted string. For a control property that needs an object no typed ABAP value can be, such as a sap.ui.integration card manifest whose keys (sap.app, sap.card) are not valid ABAP field names. Outbound only
switch_default_model	writes the binding against the named http model — where abap2UI5's own data lives once view_display( switch_default_model_path = … ) has made an OData service the view's default model, see Smart Controls

custom_mapper and custom_filter still compile but are obsolete — see Deprecations.

_bind_path( )

client->_bind_path( val ) is _bind( val = val path = abap_true ) byte for byte, delegating to it rather than repeating it. It exists because the two forms of _bind( ) read nothing alike: _bind( t_products ) says what it does, the path form needs a named val and a boolean whose name means nothing to a reader who does not know the method. It takes one parameter on purpose — the moment a second one is needed (tab, omit_initial, json), _bind( ) is the right call and path stays on it.

)->a( n = `value` v = |\{ path: '{ client->_bind_path( amount ) }', type: 'sap.ui.model.type.Float' \}|

When a Value Does Not Convert

A value travels back as text and is converted into the ABAP type behind the binding. A string that will not convert — 1,250.00 typed into an Input bound to a packed amount, letters into an integer — is skipped, not raised on: the attribute keeps its old value, the roundtrip goes on, and the browser still shows what the user typed, because the client model was updated before the request went out. The skip is traced in client->get( )-t_model_skipped, one row per refused value with the attribute name, the row and field for a table cell, and the raw text as it arrived. Read it at the top of main( ) rather than inside a Save branch, since the delta travels with whatever roundtrip follows the edit; the list is per roundtrip. Reading it pushes no model, so the refused text stays on screen until the app writes something.

The errors that do stop a roundtrip are the ones about the binding itself: BINDING_ERROR for an attribute _bind( ) cannot reach, and BINDING_ERROR_TAB_CELL_LEVEL for a cell binding whose row or component does not exist. Both are listed with their causes in Common Failures.

Data-Type Mapping

ABAP and UI5 do not share a type system. When ABAP values cross to the frontend they are serialized to JSON and then read by UI5 controls. The table below is the reference for how each ABAP type travels on the wire and which UI5 binding it pairs with. For the controls that need an explicit type: or formatter, the linked sections in Formatter show the full binding-string pattern.

ABAP type	On the wire	Typical UI5 use	Notes
string, c LENGTH n	JSON string	Input, Text	Works without a formatter.
i, int8, b, s	JSON number	Input type="Number", Text	Returned as string from inputs; cast back if you need an integer.
p LENGTH n DECIMALS m, decfloat16, decfloat34	JSON number	Input, Text + sap.ui.model.type.Float/Currency	The decimals travel as written (1234.56), no rounding through a binary float. Locale formatting needs an explicit type — see Currency.
f (binary float)	JSON number	Input, Text + sap.ui.model.type.Float	Binary float — prefer p or decfloat34 for monetary values to avoid rounding drift.
n LENGTH n	JSON string of digits	Input + sap.ui.model.odata.type.String with isDigitSequence: true	Without the constraint, leading zeros render literally — see Digit Sequence.
d	ISO date string 2024-01-15 (initial: "")	DatePicker + sap.ui.model.type.Date	Give the type a yyyy-MM-dd source pattern for explicit locale or pattern control. See Date.
t	time string 12:30:00 (initial: "")	TimePicker + sap.ui.model.type.Time	Same pattern as d, source pattern HH:mm:ss — see Time.
abap_bool (X/)	JSON true / false	CheckBox, Switch — bind it directly	The framework maps the boolean ABAP types to a JSON boolean and back, so no expression and no formatter is needed. A flag typed c LENGTH 1 instead is just a string — see Boolean.
timestamp, timestampl	JSON string, ISO in UTC (2024-01-15T12:30:00Z)	DateTimePicker + Formatter.DateCreateObject or a type with a source pattern	The Z marks UTC — see Timestamp.
utclong	JSON string, ISO-like (2026-08-21T14:00:00Z)	DateTimePicker + Formatter.DateCreateObject	Like timestamp, it arrives in a shape new Date( ) parses — see The formatters abap2UI5 ships.
xstring	binary — must be base64-encoded in ABAP before binding	Image, FileUploader, pdf_viewer	The framework does not auto-encode. Convert with cl_web_http_utility=>encode_x_base64( ) (or cl_http_utility=>if_http_utility~encode_x_base64( ) on older releases) — see PDF and Upload / Download.
structure	JSON object	Bind individual fields with struct-field	One model path per field — see Binding to Structures.
internal table	JSON array	Table, List, Tree	One row context per item — see Tables and Trees.

When a value looks wrong, the fix is almost always a UI5-side type (e.g. sap.ui.model.type.Date, sap.ui.model.type.Float) or an abap2UI5 Formatter. The shape is always the same — build a JSON binding string with parts and type, using _bind_path( ) to inject the raw model path:

)->tag( `Input`
    )->a( n = `value` v = |\{ parts: [ '{ client->_bind_path( amount ) }',|
                       && | '{ client->_bind_path( currency ) }' ],|
                       && | type: 'sap.ui.model.type.Currency' \}|

See Formatter for the full example with formatOptions, constraints, and read-only display variants.

Validation with valueState

A UI5 input shows a check result through two properties: valueState (None, Error, Warning, Success, Information) and valueStateText, the message under the field. Both are ordinary properties, so the check runs in ABAP and the result is bound like any other value — no second view, no popup:

CLASS zcl_sample_validation DEFINITION PUBLIC.

  PUBLIC SECTION.
    INTERFACES z2ui5_if_app.

    DATA mv_quantity   TYPE i.
    DATA mv_state      TYPE string VALUE `None`.
    DATA mv_state_text TYPE string.

  PROTECTED SECTION.
  PRIVATE SECTION.
ENDCLASS.

CLASS zcl_sample_validation IMPLEMENTATION.
  METHOD z2ui5_if_app~main.

    IF client->check_on_navigated( ).

      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 = `Validation`

                  )->tag( `Label`
                      )->a( n = `text` v = `Quantity (1 to 100)`
                  )->tag( `Input`
                      )->a( n = `value`          v = client->_bind( mv_quantity )
                      )->a( n = `valueState`     v = client->_bind( mv_state )
                      )->a( n = `valueStateText` v = client->_bind( mv_state_text )
                  )->tag( `Button`
                      )->a( n = `text`  v = `Save`
                      )->a( n = `press` v = client->_event( `SAVE` ) ).

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

    ELSEIF client->check_on_event( `SAVE` ).

      IF mv_quantity < 1 OR mv_quantity > 100.
        mv_state      = `Error`.
        mv_state_text = `Enter a quantity between 1 and 100`.
      ELSE.
        mv_state      = `None`.
        mv_state_text = ``.
        client->message_toast_display( `saved` ).
      ENDIF.

    ENDIF.

  ENDMETHOD.
ENDCLASS.

The SAVE branch changes two attributes and returns; the framework pushes the changed values into the view that is already on screen, and the field turns red with its text underneath. Clearing the state on success is the app's job too — a state that is never reset stays red after the user has fixed the value. For the case where the value did not even reach the attribute, see When a Value Does Not Convert above: a row of t_model_skipped is the input to the same two attributes.

Working Samples

Complete apps from the sample catalog that use what this page describes. Each is a single class in abap2UI5/samples unless its row names another of the three sample repositories — pull that repository with abapGit and start the class with ?app_start=<class>.

Sample	Class
Basics II — Data Binding: Input and Button	Z2UI5_CL_SMP_APP_494
Types for Integer, Decimal, Date and Time	Z2UI5_CL_SMP_APP_047
Structure Fields and INCLUDEs	Z2UI5_CL_SMP_APP_166
Single Table Cell (tab_index)	Z2UI5_CL_SMP_APP_144
Dynamic Table Typed at Runtime (RTTI)	Z2UI5_CL_SMP_APP_061