ABAP引數傳遞USING和CHANGIN用法總結
ABAP中FORM引數的傳遞有以下幾種方式。 1.引用傳遞(CALL BY REFERENCE) 傳遞引數時將引數的地址(ADDRESS)傳至子程式中，也就是子程式中的引數變數與外部程式的引數變數共享地址內的值。又叫CALL BY ADDRESS，若子程式中的引數變數的值發生了改變，那麼，外部程式的實際變數的值也發生改變。 [Syntax] FORM [USING …] [CHANGING …] PERFORM [USING …] [CHANGING …] USING 之後跟隨著不會發生變化的子程式引數，CHANGING後面的引數按引用傳遞，值會隨著子程式內的變化而變化。 [FOR EXAMPLE]
DATA: i_num1 TYPE I VALUE 10, i_num2 TYPE I VALUE 20, i_num3 TYPE I.
WRITE: / ‘I_NUM1=’,i_num1, ‘I_NUM2=’,i_num2, ‘I_NUM3=’,i_num3.
PERFORM CALCULATOR USING i_num1 i_num2 CHANGING i_num3. WRITE: / ‘I_NUM1=’,i_num1, ‘I_NUM2=’,i_num2, ‘I_NUM3=’,i_num3.
FORM CALCULATOR USING NUM1 NUM2 CHANGING NUM3. NUM3 = NUM1 + NUM2. WRITE: / ‘NUM1=’,NUM1, ‘NUM2=’,NUM2, ‘NUM3=’,NUM3.
"NUM1 = NUM1 + 10. "不允許修改
"NUM2 = NUM2 + 12. "不允許修改
ENDFORM.
程式執行結果如下，i_num3變數在呼叫子程式後值變為了30.
WRITE: / ‘I_NUM1=’,i_num1, ‘I_NUM2=’,i_num2, ‘I_NUM3=’,i_num3.
PERFORM CALCULATOR_TWO USING i_num1 i_num2 CHANGING i_num3. WRITE: / ‘I_NUM1=’,i_num1, ‘I_NUM2=’,i_num2, ‘I_NUM3=’,i_num3.
*值傳遞 USING VALUE(f1)
FORM CALCULATOR_TWO USING VALUE(NUM1) VALUE(NUM2) CHANGING SUM.
SUM = NUM1 + NUM2.
NUM1 = NUM1 * NUM2.
NUM2 = NUM1 * NUM2.
WRITE: / ‘NUM1=’,NUM1,
‘NUM2=’,NUM2,
‘SUM=’,SUM.
ENDFORM.
程式執行如下圖，子程式內部引數變數的值發生變數，不影響外部程式實際變數的值。
DATA: i_num1 TYPE I VALUE 10, i_num2 TYPE I VALUE 20.
WRITE: / ‘I_NUM1=’,i_num1 LEFT-JUSTIFIED, ‘I_NUM2=’,i_num2 LEFT-JUSTIFIED.
PERFORM CALCULATOR USING i_num1 i_num2. WRITE: / ‘I_NUM1=’,i_num1 LEFT-JUSTIFIED, ‘I_NUM2=’,i_num2 LEFT-JUSTIFIED.
FORM CALCULATOR USING NUM1 NUM2. WRITE: / ’ NUM1=’,NUM1 LEFT-JUSTIFIED, ’ NUM2=’,NUM2 LEFT-JUSTIFIED.
NUM1 = NUM1 + 10.
NUM2 = NUM2 + 12.
ENDFORM.
執行結果很明顯，如下圖：
WRITE: / ‘I_NUM1=’,i_num1, ‘I_NUM2=’,i_num2, ‘I_NUM3=’,i_num3.
PERFORM CALCULATOR_THREE USING i_num1 i_num2 CHANGING i_num3. WRITE: / ‘I_NUM1=’,i_num1, ‘I_NUM2=’,i_num2, ‘I_NUM3=’,i_num3.
