null set

基本解釋

When a change is made to a relationship, the related foreign-key property is set to a null value.
對(duì)關(guān)系進(jìn)行更新時(shí)，相關(guān)的外鍵的屬性設(shè)置爲(wèi)空值。
If the pszText member is non-NULL, return TRUE to set the item's label to the edited text. Return FALSE to reject the edited text and revert to the original label.
処理這個(gè)通知，查找是否有同名項(xiàng)，如果是則返廻FALSE，否則將編輯後的文字複制到節(jié)點(diǎn)。
However in this case, the link's ref attribute will be set to the value "null," and the link's text content will be hidden unless a flag to show null-link content is set to true.
但是，在這種情況下，這個(gè)鏈接的 ref 屬性會(huì)設(shè)置爲(wèi) “null” 值，而且鏈接的文本內(nèi)容會(huì)隱藏起來(lái)，除非將顯示空鏈接內(nèi)容的標(biāo)志設(shè)置爲(wèi) true。