lv_children = iv_account->get_children( iv_as_copy = abap_true ). 的參數(shù)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(shí)對于做過debug的developer，看了文檔里對這個(gè)參數(shù)的解釋后理解就會(huì)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(gè)參數(shù)關(guān)鍵起作用的地方就在container object list的構(gòu)造函數(shù)里：

如果你使用iv_as_copy = true得到一個(gè)container object list，那么這個(gè)container object list A 只是當(dāng)前parent container object的children的一個(gè)snapshot，今后parent container object 如果有新的children加進(jìn)來之后，新的child不會(huì)反映到你得到的snapshot A去，因?yàn)閠echnical上講，你的snapshot并沒有注冊 parent container object的CHILD_ADDED event，因?yàn)椴粫?huì)被通知到。

舉一個(gè)例子：

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

我新建一個(gè)Address，然后save

因?yàn)楫?dāng)前的Account DB里面有50個(gè)address，我又在當(dāng)前session里面添加了1個(gè)，所以iv_as_copy = false的有51個(gè)item，而snapshot仍然只有1個(gè)dummy的。

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