Q：怎么交換或者移動(dòng)realm數(shù)據(jù)庫里面的兩條記錄呢灶？
- 需求：
我要移動(dòng)cell或者交換cell上的兩條數(shù)據(jù)模型吴超，下次展示這個(gè)頁面以我現(xiàn)在更改的順序出現(xiàn)。 - 思路：
因?yàn)閿?shù)據(jù)是從網(wǎng)絡(luò)獲取鸯乃，然后更新數(shù)據(jù)庫鲸阻，然后讀取出來跋涣，所以要想改變順序只有兩種方法：
1.對(duì)查詢結(jié)果按照自己想要的查詢條件進(jìn)行排序，但是這樣好像每次都需要對(duì)其查詢操作鸟悴，顯然不是太好陈辱。
2.直接對(duì)realm數(shù)據(jù)庫里面的記錄進(jìn)行移動(dòng)或者交換，于是去查詢r(jià)ealm的源代碼细诸，發(fā)現(xiàn)了兩個(gè)方法：
移動(dòng)和交換
具體實(shí)現(xiàn)方法如下：
/**
Replaces an object at the given index with a new object.
- warning: This method may only be called during a write transaction.
- warning: This method will throw an exception if called with an invalid index.
- parameter index: The index of the object to be replaced.
- parameter object: An object.
*/
public func move(from from: Int, to: Int) { // swiftlint:disable:this variable_name
throwForNegativeIndex(from)
throwForNegativeIndex(to)
_rlmArray.moveObjectAtIndex(UInt(from), toIndex: UInt(to))
}
/**
Exchanges the objects in the list at given indices.
- warning: This method may only be called during a write transaction.
- warning: This method will throw an exception if called with invalid indices.
- parameter index1: The index of the object which should replace the object at index `index2`.
- parameter index2: The index of the object which should replace the object at index `index1`.
*/
public func swap(index1: Int, _ index2: Int) {
throwForNegativeIndex(index1, parameterName: "index1")
throwForNegativeIndex(index2, parameterName: "index2")
_rlmArray.exchangeObjectAtIndex(UInt(index1), withObjectAtIndex: UInt(index2))
}
使用：
realm數(shù)據(jù)庫因?yàn)槭菬o序的沛贪，但是它提供了一個(gè)List類型的集合（關(guān)于List的介紹可以去看官方文檔），被加入到List集合中的Object可以保證有序的插入震贵，所以利赋，假如我要改變文章ArticleDAO模型的展示順序，那么我可以新建一個(gè)ArticleDAOList模型猩系，然后添加：
let list = List<ArticleDAO>()
來存放ArticleDAO媚送，這樣ArtucleDAO的插入順序就可以保證了，將ArticleDAOList寇甸，存入數(shù)據(jù)庫塘偎。如果需要更改順序，那么直接更新ArticleDAOList順序拿霉，然后再更新數(shù)據(jù)庫即可
