When the user of your application edits records in masks, he usually changes field contents. DataView calls userexits at fields when the user enters or leaves fields with the write-cursor in mask edit state. Calling the various userexits at the field you can activate program functions that refer to the field entries. For instance you can request field contents, check for entries, calculate depending field entries or initiate program functions depending on field contents.
In DataView two triggers are available for calling userexits at fields. The pre_field-trigger is passed when the user enters the field with the cursor, while the post_field-trigger is passed when he leaves the field. The field triggers only work in Insert- and Update mode of Mask-Edit state, but not in Query- and View mode.
The field functionality you install via field userexits at the triggers of fields is not defined at the system object field in DataView. For you can apply a field in several masks, field userexits must always be invoked at the mask-field assignment. Though a field can be contained in several masks it is useful to assign its functionality to each corresponding mask (e.g. the post_field-trigger at the bill-of-material-field in the master list only results in a uniqueness check, while in the bill of material list a new relation can be generated).
Note! You cannot perform a mouse double click on hyperlink fields. As the mouse double click is a frequently used means for quick editing (dal_cch_sel_dtv at the Select_Action trigger), you should not use the hyperlink functionality for fields which have to be edited often. In this case you should offer the required functions in the context menu or in the context button area.