更新时间:2023-11-30 23:07:40
按照有关阵列的官方文档:
虽然Cloud Firestore可以存储数组,
但它不支持
查询数组成员或更新单个数组元素。
Although Cloud Firestore can store arrays,
it does not support
querying array members or updating single array elements.
如果您只想获得整个论文
数组,则需要迭代 Map
,如下所示:
If you only want to get the entire papers
array you need to iterate over a Map
like this:
Map<String, Object> map = document.getData();
for (Map.Entry<String, Object> entry : map.entrySet()) {
if (entry.getKey().equals("papers")) {
Log.d("TAG", entry.getValue().toString());
}
}
但请注意,即使论文
对象作为数组存储在数据库中, entry.getValue()
返回 ArrayList
,而不是数组
。
But note, even if papers
object is stored in the database as an array, entry.getValue()
returns an ArrayList
, not an array
.
编辑2018年8月13日:
根据有关数组成员资格,现在可以使用 whereArrayContains()
方法根据数组值过滤数据。一个简单的例子是:
According to the updated documentation regarding array membership, now it is possible to filter data based on array values using whereArrayContains()
method. A simple example would be:
CollectionReference citiesRef = db.collection("cities");
citiesRef.whereArrayContains("regions", "west_coast");
此查询返回每个城市文档,其中regions字段是一个数组包含west_coast。如果数组具有您查询的值的多个实例,则文档仅包含在结果中一次。
This query returns every city document where the regions field is an array that contains west_coast. If the array has multiple instances of the value you query on, the document is included in the results only once.