1、需求背景

当程序中有互为层级的字段，需要使用搜索帮助时，可以通过多次调用搜索帮助来实现。比如在程序中需要填写省市区三级地址

2、实现方式

2.1、平铺直叙

程序的搜索帮助，通常使用F4IF_INT_TABLE_VALUE_REQUEST来实现。多级的搜索帮助，可以简单的通过多次调用F4函数来实现。

点击省字段，弹出省搜索帮助，根据选择的省份，查询对应的市，弹出市搜索帮助，根据选择的市，查询对应的区县，弹出区县搜索帮助，选择后更新到ALV报表。

同理，点击市则弹出市和区的搜索帮助；点击区则只弹出区的搜索帮助

如图所示：

点击省字段代码示例，省需要写三遍F4：

"--------------------@斌将军--------------------
READ TABLE gt_cjso_alv ASSIGNING <fs_cjso_alv> INDEX pv_row_no-row_id."获取对应数据集CASE lv_fieldname1.WHEN 'ZZDEADREGION'."送货地址-省SELECTland1,bland AS zzdeadregion,bezeiFROM t005uINTO TABLE @DATA(lt_t005u)WHERE land1 EQ 'CN'AND spras EQ @sy-langu.ASSIGN lt_t005u TO <lt_f4table>.REFRESH gt_return.CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'EXPORTINGretfield        = lv_fieldname1dynpprog        = sy-repiddynpnr          = sy-dynnrdynprofield     = lv_fieldname2value_org       = 'S'display         = 'F'TABLESvalue_tab       = <lt_f4table>return_tab      = gt_returnEXCEPTIONSparameter_error = 1no_values_found = 2OTHERS          = 3.IF sy-subrc =  0.READ TABLE gt_return INTO gs_return INDEX 1.IF sy-subrc = 0.ASSIGN COMPONENT lv_fieldname1 OF STRUCTURE <fs_cjso_alv> TO <lv_field>.<lv_field> = gs_return-fieldval.SELECTcountry,region,city_code AS zzdeadcity,city_nameFROM v_adrcityINTO TABLE @DATA(lt_v_adrcity)WHERE country EQ 'CN'AND langu  EQ @sy-languAND region EQ @<fs_cjso_alv>-zzdeadregion.ASSIGN lt_v_adrcity TO <lt_f4table>.lv_fieldname = 'ZZDEADCITY'.lv_dynprofld = 'ZZDEADCITY'.REFRESH gt_return.CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'EXPORTINGretfield        = lv_fieldnamedynpprog        = sy-repiddynpnr          = sy-dynnrdynprofield     = lv_dynprofldvalue_org       = 'S'display         = 'F'TABLESvalue_tab       = <lt_f4table>return_tab      = gt_returnEXCEPTIONSparameter_error = 1no_values_found = 2OTHERS          = 3.IF sy-subrc =  0.READ TABLE gt_return INTO gs_return INDEX 1.IF sy-subrc = 0.ASSIGN COMPONENT 'ZZDEADCITY' OF STRUCTURE <fs_cjso_alv> TO <lv_field>.<lv_field> = gs_return-fieldval.lv_zzdeadcity = |{ <fs_cjso_alv>-zzdeadcity ALPHA = IN }|.SELECTcountry,city_code,city_name,strt_code AS zzdeadstreet,streetFROM m_strtaINTO TABLE @DATA(lt_m_strta)WHERE country EQ 'CN'AND langu  EQ @sy-languAND region EQ @<fs_cjso_alv>-zzdeadregionAND city_code EQ @lv_zzdeadcity.ASSIGN lt_m_strta TO <lt_f4table>.lv_fieldname = 'ZZDEADSTREET'.lv_dynprofld = 'ZZDEADSTREET'.REFRESH gt_return.CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'EXPORTINGretfield        = lv_fieldnamedynpprog        = sy-repiddynpnr          = sy-dynnrdynprofield     = lv_dynprofldvalue_org       = 'S'display         = 'F'TABLESvalue_tab       = <lt_f4table>return_tab      = gt_returnEXCEPTIONSparameter_error = 1no_values_found = 2OTHERS          = 3.IF sy-subrc =  0.READ TABLE gt_return INTO gs_return INDEX 1.IF sy-subrc = 0.ASSIGN COMPONENT 'ZZDEADSTREET' OF STRUCTURE <fs_cjso_alv> TO <lv_field>.<lv_field> = gs_return-fieldval.ENDIF.ENDIF.ENDIF.ENDIF.ENDIF.ENDIF.WHEN 'ZZDEADCITY'."送货地址-市……WHEN 'ZZDEADSTREET'."送货地址-区县……WHEN OTHERS.ENDCASE.PERFORM frm_refresh_alv USING g_grid_9001.
"--------------------@斌将军--------------------

2.2、简洁递归

上述方法，虽然能够实现，但是三级地址就需要写五遍重复性代码，如果遇到层级更多的搜索帮助，则需要写N(N+1)/2遍代码，所以我们可以使用递归函数，重复调用搜索帮助，使代码更简洁。

这里说明一点，什么是递归函数？

递归函数：在函数内部调用自身的函数被称为递归函数。递归函数可以将复杂问题转化为更简单的子问题来解决。一个经典的递归函数例子是阶乘函数，其中 n! 等于 n 乘以 (n-1)!。在函数内部通过调用自身来计算阶乘。

抽出通用代码，编写递归函数

"--------------------@斌将军--------------------
FORM frm_callback_f4 USING pv_level pv_fieldname CHANGING ps_alv TYPE ty_cjso_alv.*  DATA:lv_zzdeadcity   TYPE vbak-zzdeadcity. "送货地址-市DATA:lt_return TYPE STANDARD TABLE OF ddshretval,ls_return TYPE ddshretval.DATA:lv_next_field TYPE dfies-fieldname,lv_next_level TYPE int4,lv_fieldname  TYPE dfies-fieldname,lv_dynprofld  TYPE help_info-dynprofld.FIELD-SYMBOLS:<lv_field>.lv_fieldname = pv_fieldname.lv_dynprofld = pv_fieldname.CONDENSE:lv_fieldname,lv_dynprofld NO-GAPS.lv_next_level = pv_level."根据层级，查询当前层级的数据集，并赋值下一层的字段名CASE lv_next_level.WHEN 1."第1层 省SELECTland1,bland AS zzdeadregion,bezeiFROM t005uINTO TABLE @DATA(lt_t005u)WHERE land1 EQ 'CN'AND spras EQ @sy-langu.UNASSIGN <gt_f4table>.ASSIGN lt_t005u TO <gt_f4table>.lv_next_field = 'ZZDEADCITY'.WHEN 2."第2层 市SELECTcountry,region,city_code AS zzdeadcity,city_nameFROM v_adrcityINTO TABLE @DATA(lt_v_adrcity)WHERE country EQ 'CN'AND langu  EQ @sy-languAND region EQ @ps_alv-zzdeadregion.UNASSIGN <gt_f4table>.ASSIGN lt_v_adrcity TO <gt_f4table>.lv_next_field = 'ZZDEADSTREET'.WHEN 3."第3层 区DATA(lv_zzdeadcity) = |{ ps_alv-zzdeadcity ALPHA = IN }|.SELECTcountry,city_code,city_name,strt_code AS zzdeadstreet,streetFROM m_strtaINTO TABLE @DATA(lt_m_strta)WHERE country EQ 'CN'AND langu  EQ @sy-languAND region EQ @ps_alv-zzdeadregionAND city_code EQ @lv_zzdeadcity.UNASSIGN <gt_f4table>.ASSIGN lt_m_strta TO <gt_f4table>.WHEN OTHERS.ENDCASE."调用搜索帮助函数CALL FUNCTION 'F4IF_INT_TABLE_VALUE_REQUEST'EXPORTINGretfield        = lv_fieldnamedynpprog        = sy-repiddynpnr          = sy-dynnrdynprofield     = lv_dynprofldvalue_org       = 'S'display         = 'F'TABLESvalue_tab       = <gt_f4table>return_tab      = lt_returnEXCEPTIONSparameter_error = 1no_values_found = 2OTHERS          = 3.IF sy-subrc =  0.READ TABLE lt_return INTO ls_return INDEX 1.IF sy-subrc = 0.ASSIGN COMPONENT lv_fieldname OF STRUCTURE ps_alv TO <lv_field>.<lv_field> = ls_return-fieldval.IF lv_next_level < 3."第三层查询完退出lv_next_level = lv_next_level + 1."调用函数本身，开始下次循环PERFORM frm_callback_f4 USING lv_next_level lv_next_field CHANGING ps_alv.ENDIF.ENDIF.ENDIF.
ENDFORM.
"--------------------@斌将军--------------------

在点击字段时调用，通过赋值层级，就可以循环调用多级搜索帮助，且代码更加简洁，复用性更高

"--------------------@斌将军--------------------
FORM frm_alv_on_f4_9001 USING pv_fieldname pv_fieldvalue pv_row_no TYPE lvc_s_roidpv_event_data TYPE REF TO cl_alv_event_datapv_display.READ TABLE gt_cjso_alv ASSIGNING <fs_cjso_alv> INDEX pv_row_no-row_id."获取对应数据集CASE pv_fieldname.WHEN 'ZZDEADREGION'."送货地址-省PERFORM frm_callback_f4 USING 1 'ZZDEADREGION' CHANGING <fs_cjso_alv>.WHEN 'ZZDEADCITY'."送货地址-市PERFORM frm_callback_f4 USING 2 'ZZDEADCITY' CHANGING <fs_cjso_alv>.WHEN 'ZZDEADSTREET'."送货地址-区县PERFORM frm_callback_f4 USING 3 'ZZDEADSTREET' CHANGING <fs_cjso_alv>.WHEN OTHERS.ENDCASE.PERFORM frm_refresh_alv USING g_grid_9001.ENDFORM.
"--------------------@斌将军--------------------

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