How to Use Filters 

Recalling from the previous step (How to Implement a BAdI), you need a way to select between different BAdI implementations. This is where you need the BAdI filter.

What you need is to change the BAdI definition. You can define one or many filters for a BAdI. For the purpose of this example, you create only one filter. Therefore, in this step you define the filter in the BAdI definition, determine filter values for the respective BAdI implementation, and use the filter in the instantiation of the BAdI handle.

When modifying your example you do not take into account the differentiation between the BAdI provider and the implementer. In real life it is the BAdI provider who defines a BAdI with a filter or adds a filter to an existing BAdI. It is also part of this role to use the filter condition to select the respective BAdI implementation in the ABAP code. It is the implementer who determines the filter value(s) or an interval for one or many BAdI implementations.

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       1.      Navigate to your enhancement spot and open the Enh. Spot Element Definition tab that shows a list of all the enhancement elements of the spot.

       2.      Switch to a change mode, select your BAdI in the list, and in the small toolbar above choose Create BAdI Subobject icon and then Filter.

       3.      The following dialog appears, where you fill in the corresponding fields:

       4.      Confirm the entries.

The filter is now visible as a property below the BAdI.

       5.      Activate the enhancement spot, double-click on the implementation and navigate to the respective BAdI implementation by double-clicking the respective row in the table of BAdI implementations.

       6.      Switch to change mode, double-click the triangle in front of the BAdI implementation in the tree and then double-click on the filter icon below.

       7.      On the Filter Values screen, choose the Create Filter Combination pushbutton.

       8.      Select Country as the filter and confirm

       9.      Double-click on the row below Combination 1.

A new dialog opens:

 

   10.      Activate the (simple) enhancement implementation and navigate back to the spot.

The other implementation, that is the one for USA, also needs the respective filter value. So you go to the respective (simple) enhancement implementation and change the BAdI implementation in the same way as you just did above. The respective filter value for this country is 'US'.

   11.      Return to your program and adapt it to the modified BAdI. Running the syntax check shows you that you need to have a filter parameter in the GET BADI command if the BAdI you try to instantiate is defined with a filter. The required addition to the GET BADI command is FILTERS. It is after this keyword that you insert the name of the BAdI filter and a value the filter is compared to. You also have to take care that an appropriate value can be passed to the GET BADI routine:

REPORT  Z_DEMO_ENH.

parameters: ctry(2) type c.

DATA: handle TYPE REF TO z_badi_calc_vat,

sum TYPE p,

vat TYPE p,

percent TYPE p.

sum = 50.

GET BADI handle FILTERS Country = ctry.

CALL BADI handle->get_vat

  EXPORTING im_amount = sum

  IMPORTING ex_amount_vat = vat

         ex_percent_vat = percent.

WRITE: 'percentage:', percent, 'VAT:' ,vat.

If you pass GB to the parameter ctry, you get a VAT rate of 17.5 percent. If the value of the parameter ctry is US, the VAT rate is 4 percent. When the parameter ctry has any other value, you still get a calculated value for the data field percent. This is because you have defined a fallback class for your BAdI. The fallback class is not only selected if no BAdI implementation is available, but also if none of the existing BAdI implementations meets the filter conditions in the GET BADI command. Accordingly, you get a VAT rate of 20 percent, which is the VAT rate you have implemented in the method get_vat in the fallback class.