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ST - tt:loop, Internal Tables

Other versions: 7.31 | 7.40 | 7.54


<tt:loop [ref="node"] [name="alias"]> 


Internal tables are serialized and deserialized within a loop defined by tt:loop that sets the current node to the current table row.

The optional attribute ref can be used to define the current node for the command. If ref is not specified, the current node of the surrounding element is used. The ABAP data object that is bound to the current node must be an internal table.

The name attribute can be used to define an alias for the current node within the loop. In the tt:loop loop, the current node can then be addressed with $alias. When nested loops are used, the alias permits access to the current nodes of outer loops. If only one loop is used and in the outermost loop, $alias is equivalent to $ref when entering the loop.


During serialization, a loop is run for the entire internal table. If the internal table is blank, processing continues after the element. During each loop pass, the current node of a data node is set and the current ABAP table row is bound to the data node. The content of element tt:loop, which can contain any template elements, is processed for each data node.


During the deserialization process, the ABAP table is initialized and the content of element tt:loop is also executed in a loop. The XML document continues to be processed until a position is reached that cannot be processed with the content of the element. A new line is generated in the bound ABAP table for each loop pass and is in turn bound to the current node. The XML values that are deserialized in the current loop pass are passed on to the current table row.


  • If you want to be able to deserialize a transformation, you have to make sure that loop execution can be ended properly, especially in the case of nested tt:loop loops. This is the case when the content of a tt:loop element can be synchronized with the sections to be deserialized. If the XML elements in a loop are not sufficient, the entire loop body can be enclosed with a literal XML element, for example, which defines a hierarchy level that can be analyzed during the deserialization process.

  • In a Simple Transformation, a data node must be treated either exclusively as an internal table or not at all. In particular, this applies to dividing a template into different transformation directions.


In the following symmetrical Simple Transformation, the internal table that is bound to the ROOT data roots and its table-like component values are serialized and deserialized in two nested tt:loop loops. For demonstration purposes, an alias called line is defined in the outermost loop and is addressed in the loop using $line. Since $line is not addressed in the inner loop, the definition of the alias name would not be necessary here.

  <tt:root name="ROOT"/>
      <tt:loop ref=".ROOT" name="line">
          <tt:value ref="$line.key" />
          <tt:loop ref="$line.values">

The following ABAP program can call the transformation:

DATA xml_string TYPE string.

        key TYPE i,
        values TYPE TABLE OF i,
      END OF line.

DATA num TYPE i.

DATA result LIKE itab.

  CLEAR line.
  line-key = sy-index + 1.
  num = line-key ** 2.
  APPEND num TO line-values.
  num = line-key ** 3.
  APPEND num TO line-values.
  num = line-key ** 4.
  APPEND num TO line-values.
  APPEND line TO itab.

  SOURCE root = itab
  RESULT XML xml_string.

cl_abap_browser=>show_xml( EXPORTING xml_string = xml_string ).

  SOURCE XML xml_string
  RESULT root = result.

The result of the serialization is the following:


The transformation is symmetrical. After deserialization, result has the same content as itab.