Flutter 将 QuerySnapshot 转换为 Future <List<Map<dynamic, dynamic>>>.

Question

如何将QuerySnapshot作为Future返回？

代码片段：

Future <List<Map<dynamic, dynamic>>>() {
List<Map<dynamic,dynamic>> list;
.....

.....
QuerySnapshot collectionSnapshot = await collectionRef.getDocuments();

list = collectionSnapshot.documents;  <--- ERROR
return list;

}

我认为我需要使用一个 Map，但是我无法解决它的问题。

- LiveRock

Answer 1

collectionSnapshot.documents返回的是List而不是List类型，您需要将documentsnapshots的List转换为List<Map<dynamic, dynamic>>。

Future <List<Map<dynamic, dynamic>>> getCollection() async{
List<DocumentSnapshot> templist;
List<Map<dynamic, dynamic>> list = new List();
CollectionReference collectionRef = Firestore.instance.collection("path");
QuerySnapshot collectionSnapshot = await collectionRef.getDocuments();

templist = collectionSnapshot.documents; // <--- ERROR

list = templist.map((DocumentSnapshot docSnapshot){
  return docSnapshot.data;
}).toList();

return list;
}  

- Ganapat

Answer 2

Ganapat的答案对我有所帮助，只需进行一些小修改即可。

Future <List<Map<dynamic, dynamic>>> getCollection() async{
List<DocumentSnapshot> templist;
List<Map<dynamic, dynamic>> list = new List();
CollectionReference collectionRef = Firestore.instance.collection("path");
QuerySnapshot collectionSnapshot = await collectionRef.get(); // <--- This method is now get().

templist = collectionSnapshot.documents; // <--- ERROR

list = templist.map((DocumentSnapshot docSnapshot){
  return docSnapshot.data() as Map<Dynamic,Dynamic>; // <--- Typecast this.
}).toList();

 

return list;
}  

- DevSec Guy

---

小写形式：return docSnapshot.data() as Map<dynamic, dynamic>; - threepartment