Typo3 - Use FlexForm value for DataQueryProcessor in TypoScript

I have a content element that stores values in a FlexForm (eg. 1234). The value represents an UID of a database table.

What i want to do:

• Get the single value which is stored in the FlexForm (Already working)
• Run a database query with this value
• Show the data in the frontend

Problem: I don't know how to hand over the FlexForm value to the where-clause of the DB query.

tt_content {
  my_addresscontainer =< lib.contentElement
  my_addresscontainer {

    templateName = AddressContainer
    templateRootPaths {
      10 = EXT:xyz/Resources/Private/Partials/ContentElements/
    }
    partialRootPaths {
      10 = EXT:xyz/Resources/Private/Partials
    }

    dataProcessing {
        1 = xyz\DataProcessing\FlexFormProcessor
        1 {
            options {
                if.isTrue.field = pi_flexform
                fieldName = pi_flexform
            }
            as = content
        }

        10 = TYPO3\CMS\Frontend\DataProcessing\DatabaseQueryProcessor
               10 {
                  table = tt_address
                  pidInList = 19
                  markers {
                        myuid.value = 191901 <- This should be handed over...
                  }
                  where = uid =###myuid###
                  as = address_record
                }
    }
  }
}

Thank you in advance.

If you just want to access the flexform value from your plugin/content element you can do that without a custom FlexFormProcessor. Use the data type flexform, e.g. like this:

dataProcessing {
  10 = TYPO3\CMS\Frontend\DataProcessing\DatabaseQueryProcessor
  10 {
    table = tt_address
    pidInList = 19
    uidInList.data = flexform:pi_flexform:settings.myuid
  }
}

You need to adjust settings.myuid according to the naming in your flexform. See the TypoScript Reference for details on the data type flexform.

If you need your custom FlexFormProcessor, you need to nest the dataProcessing, something like this:

dataProcessing {
  1 = xyz\DataProcessing\FlexFormProcessor
  1 {
    options {
      if.isTrue.field = pi_flexform
      fieldName = pi_flexform
    }
    as = content

    dataProcessing {
      1 = TYPO3\CMS\Frontend\DataProcessing\DatabaseQueryProcessor
      1 {
        table = tt_address
        pidInList = 19
        markers {
              myuid.value = 191901 <- This should be handed over...
        }
        where.wrap = uid =|
        as = address_record
      }
    }
  }
}

The important line is the where.wrap where you use the value from the first dataProcessing.