SAP CRM get_children 方法裏面參數 iv_as_copy 有什麼用？

• 2020 年 2 月 14 日
• 筆記

lv_children = iv_account->get_children( iv_as_copy = abap_true ). 的參數啥意思 lo_children = iv_account->get_relation( iv_relation_name = iv_as_copy = abap_false ).

解釋沒太看懂

There is one special thing you need to know on the parameter IV_AS_COPY of GET_CHILDREN. It has only effect on the iterator GET_FIRST etc. of the container list you will receive back. If set to true the iterator will iterate only on the children inside the container list when it was created. If the parameter is set to false the iterator will take into account children that are added to the container (or which are deleted from it) after the container list was get. It is a misunderstanding that you get a copy of the content of the container if you use this parameter. Knowing this you now have the knowledge going through the relations of your model getting a separate nested container for every 1:n relation.

Rule of thumb:

(1) iv_as_copy = true => you get a snapshot (preffered) (2) iv_as_copy = false => list gets updated; use only if you want to keep the list; has negative impact on performance/memory consumption

其實對於做過debug的developer，看了文檔里對這個參數的解釋後理解就會更加深刻。但是的確剛剛接觸的developer看了解釋可能仍然似懂非懂。

這個參數關鍵起作用的地方就在container object list的構造函數里：

如果你使用iv_as_copy = true得到一個container object list，那麼這個container object list A 只是當前parent container object的children的一個snapshot，今後parent container object 如果有新的children加進來之後，新的child不會反映到你得到的snapshot A去，因為technical上講，你的snapshot並沒有註冊 parent container object的CHILD_ADDED event，因為不會被通知到。

舉一個例子：

我在從Account navigate 到AccountAddress的地方加一段代碼，分別存儲兩種方式得到的account address container object list，這個時候還沒有真正取Account address,所以兩個container object list裏面都只有一個dummy的entry，is_handle = X

我新建一個Address，然後save

因為當前的Account DB裏面有50個address，我又在當前session裏面添加了1個，所以iv_as_copy = false的有51個item，而snapshot仍然只有1個dummy的。