ABAP Basic Concept (2) 運算子 控制式與迴圈 Subroutines Event Block IF, CASE, DO… ENDDO Subroutines Call by value, value and result, reference Event Block Initialization, Start-of-Selection, At Line-Selection
1. 運算子 比較運算子 = , <> , < , <= , > , >= 比較運算子 = , <> , < , <= , > , >= 算數運算子 + , - , * , /, mod (餘數) 邏輯運算子 AND , OR
2. 控制式與迴圈 IF子句 IF <Logical Expression> . <Statements>. ELSEIF <Logical Expression> . <Statements>. ELSE . <Statements>. ENDIF . CASE子句 CASE < variable > . WHEN 'value1' . <Statements>. WHEN 'value2' OR 'value3' . <Statements>. WHEN OTHERS . <Statements>. ENDCASE .
控制式與迴圈 (Cont.) DO…ENDDO子句 DO 整數變數 TIMES. ENDDO. 範例： DATA X TYPE I. DATA N TYPE I. X = 1. N = 5. DO N TIMES. WRITE: / X. X = X + 1.
3. Subroutines 第一行以FORM開始，最後一行以ENDFORM結束
參數傳遞方式 相同記憶體位址 CHANGING fv3 USING VALUE (fv1) 不同位址，但回傳後更改其值 呼叫副程式 USING VALUE (fv1) 不同位址，但回傳後更改其值 CHANGING VALUE (fv2) 相同記憶體位址 CHANGING fv3 CHANGING
練習F 計算總和副程式 (程式名稱zyy**_ex_f) 定義整數變數n，並設定n為6，請分別呼叫以下兩支副程式，再印出n值。 副程式1：利用call by value 根據傳來的n值，印出n平方 副程式2：利用call by reference
練習F參考解答 REPORT zyyTC_EX_F . DATA N TYPE I. N = 6. PERFORM SQUARE1 USING N. WRITE: / 'N=', N. ULINE. PERFORM SQUARE2 CHANGING N. FORM SQUARE1 USING VALUE(X). X = X * X. WRITE: / 'Square1: N^2=', X. ENDFORM. FORM SQUARE2 CHANGING X.
4. Event Block 類似視窗系統之事件，無一定之執行順序，而由 runtime system 所決定 用法: 第一行以keyword為起始，無結束keyword 直到遇到下一個event block或FORM keyword才結束
Event Blocks for Reports
Event Blocks for Reports (Cont.) The runtime environment creates the INITIALIZATION event and calls the event block. If there is a selection screen defined in the program, control returns to the selection screen processor. Control then passes to the reporting processor. It creates the START-OF-SELECTION event. The logical database, if you are using one, calls further event blocks at this point. The reporting processor creates the END-OF-SELECTION event. If the program contains a list description, it displays the list defined in the AT LINE-SELECTION event.
Major Event Blocks 設定初值 Basic list要用到的 event，用來產生report 範例 PARAMETERS INPUTN TYPE I. START-OF-SELECTION. IF INPUTN = 1 . WRITE : 'HI!'. ENDIF.